Search

The editorial discusses the complexities of solidification in metallic materials, emphasizing the importance of understanding variables like cooling rate and thermal gradient for predicting cast product performance. The special issue focuses on casting alloy design and characterization, with studies covering topics such as high-entropy alloys, Fe-based and Co-based multicomponent alloys, and unconventional rheocasting processes for Al-Si alloys. The research aims to establish correlations between processing, properties, and microstructures, offering insights into improving casting processes and developing high-quality cast products. The editorial concludes by highlighting the significance of microstructure in determining casting properties and the need for continued investigation in casting alloy design and characterization. [Extracted from the article]

Carburizing and quenching can endow the gear with a hardening depth, improving the part's hardness and contact fatigue strength while distorting the part, resulting in increased or uneven subsequent grinding allowances and reduced part precision. Therefore, cooperative control of hardening depth and distortion is critical. Here, the temperature, phase transition, hardness of carburizing and quenching, and the numerical strain model after die unloading were analyzed to predict the hardening depth and deformation of die quenching. Numerical model is the mathematical essence of finite element model (FEM), based on numerical model, a face gear die-quenching FEM was established to predict the hardening depth and deformation of die quenching, which was verified through carburizing and die-quenching experiments. Based on the FEM, the simulation results under multiple process parameters can be obtained. Further, using the results can built a neural network surrogate model to describe the relationship between carburizing and quenching process parameters and hardening depth and deformation. Additionally, the non-dominated sorting genetic algorithm (NSGA-II) was used to optimize the parameters of the heat treatment process, which are able to control the deformation under the condition of satisfying hardening depth. Finally, a "simulation-surrogation-optimization" model was proposed to simulate the process of carburizing and die quenching of parts, predict the deformation and hardening depth of parts, and give the optimal process parameters under certain process requirements. The results revealed that the martensite content and the deformation of the face gear increased as the carbon content increased from the surface to the center of the face gear. As the die pressure increased, the overall deformation of the face gear using die quenching decreased gradually. However, the excessive pressure caused severe distortion to the tooth height. Using appropriate pressure for die quenching not only controlled the face gear's warping but also reduced its diameter shrinkage. [ABSTRACT FROM AUTHOR]

The development of high-strength advanced additively manufactured (AM) aluminum alloys is driven by the need for weight reduction in complex-shaped structural applications. In this context, heat-treatable aluminum-scandium alloy, known commercially as Scalmalloy®, offers high strength and lightness, also at high temperatures, due to solution strengthening Al3(Sc, Zr) particles. A widespread diffusion of such AM alloy is also related to welding technologies that could preserve its engineered microstructure. This study investigates the microstructural and mechanical properties of butt friction stir welding (FSW) joints of LPBF Scalmalloy® plates under different welding settings. Joint performance was evaluated under quasi-static and cyclic loading conditions. Porosity in Scalmalloy® and welds was assessed using 3D X-ray computed tomography. An aging heat treatment assessed the extent of precipitation hardening in the FSW joints. Results show that metal stirring during FSW notably reduced the intrinsic porosity of Scalmalloy®, decreasing the equivalent pore diameter from about 200 μm to 60 μm in the welded joints. Under quasi-static loading, welded specimens failed at the interface between the thermo-mechanically affected and the stir zones on the advancing side. The aging heat treatment improved the mechanical strength of Scalmalloy® from approximately 400 to 480 MPa, albeit at the expense of ductility (elongation at fracture decreased from 16 to 4%). The higher heat input and stirring developed at a low welding speed reduced lazy S defects but limited the effectiveness of subsequent aging. In fatigue testing, welded joints consistently failed within the aged base material due to the intrinsic porosity of Scalmalloy®. [ABSTRACT FROM AUTHOR]

We study Inconel 718 refractory alloy produced by using different modes of electron beam melting. The phase composition and specific features of the microstructure of alloy are analyzed both in the initial state and after hardening heat treatment. The fracture surfaces of the samples of alloy are analyzed after uniaxial tensile tests. It is shown that the fracture of the material occurs according to the ductile mechanism. However, fracture surfaces contain significant amounts of defects in the form of unmolten areas and porosity, which is typical of the products obtained by using additive technologies from powder materials. It is shown that the fracture of the analyzed alloy is provoked by the presence of unmolten areas and intermetallic particles of the δ-phase in the structure. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The primary goal of this research is to develop hybrid non-ferrous material composites with high flexural and impact strengths by testing the mechanical, thermal, and corrosion properties of AA 6061 wheel rims with various silicon carbide (SiC) and zirconium sulphide (ZrSO4) compositions. This produces an alloy with high strength and perceptible hardenability that is used in a variety of marine space industries. Because of its exceptional strength-to-density ratio, it is a highly sought-after metal matrix composite in the automobile industry. This innovative composite material offers lower weight and higher impact strength when compared to the current wheel rim alloy. Designs of experiments based recommendations and results of simulations in order to prolong the life of the wheel rim. [ABSTRACT FROM AUTHOR]

Metal manufacturing processes based on deformation (forging, rolling) result in a fine grain structure with a complex dislocation substructure, which positively influence mechanical properties. Casting and additive manufacturing (powder- or wire-based) usually produce a coarse grain structure with a poorly developed dislocation substructure, which negatively affect mechanical properties. Heat treatment may alter phase balance and stimulate precipitation strengthening; however, precipitation kinetics depends on the dislocation substructure. In this paper, a comparative study of the microstructure and strength is presented for Monel K500 alloy containing 63 Ni, 30 Cu, 2.0 Mn, and 2.0 Fe (wt.%), and microalloyed with Al, Ti, and C hot-rolled to a round bar and deposited on a round surface using wire additive manufacturing (WAAM) technology. An increased dislocation density and number density of fine precipitates resulted in 8–25% higher hardness and 1.8–2.6 times higher compression yield stress in the hot-rolled alloy compared to these in the WAAM-produced alloy. However, due to a high work hardening rate, only 3–10% cold deformation was necessary to increase the strength of the WAAM alloy to this of the hot-rolled one. Age hardening heat treatment, through the intensification of the precipitation strengthening mechanism, reduced the value of cold deformation strain required to equalise the properties. Based on the obtained results, a new technology consisting of additive manufacturing, heat treatment, and cold deformation can be proposed. It can produce WAAM components with strength and hardness improved to the level of hot-rolled components, which is a significant development of additive manufacturing. [ABSTRACT FROM AUTHOR]

To improve the machinability properties of CuZn-alloys, these are alloyed with the element lead. Due to its toxicity, a variety of legislative initiatives aim to reduce the lead content in CuZn-alloys, which results in critical machinability problems and a reduction in the productivity of machining processes. Basically, there are two ways to solve the critical machinability problems when machining lead-free CuZn-alloys: optimizing the machinability of lead-free materials on the material side or adapting the processes and the respective process parameters. In this study, the focus is on material-side machinability optimization by investigating the influence of a targeted variation in the process chain in the material production route. To evaluate the influence of the material production route, the brass alloy CuZn40 (CW509L) was produced in four variants by varying the degree of work hardening and the use of heat treatments, and all four variants were evaluated in terms of their machinability. To evaluate the machinability, the cutting force components, the chip temperature, the chip formation, and the chip shape were analyzed. Clear influences of the material production route were identified, particularly with regard to the chip formation mechanisms and the resulting chip shape. [ABSTRACT FROM AUTHOR]

Hardening heat treatment is one of the most important processes used in manufacturing the oil extraction machine’s cylinder. During heating operations, thermal stresses are created. This would lead to internal defects because of screw pressure and finally cause failure and decreases in machine life time. In this paper, different heating heat treatment cycles for an oil extraction machine’s cylinder made of stainless steel AISI420 were investigated by experimental and numerical methods. Since the residual stress is the main factor that affects the failure in the cylinder, the cycle with minimum stress is chosen as an optimum condition. The accuracy of the results of the simulation process is evaluated by providing experimental samples. Also, different heat treatment cycles were designed by the TAGUCHI method. Then, tensile test specimens were prepared from experimental samples, and their mechanical properties were compared. Finally, preheating at 790 °C for 30 minutes, the second stage preheating at 900 °C for 30 minutes, the Austenitic process at 1056 °C for 30 minutes, Quenching in oil at 80 °C for 10 minutes, the first stage tempering process at 370 °C for 90 minutes and the second stage tempering process at 370 °C for 90 minutes was considered as the best condition for hardening heat treatment cycles. [ABSTRACT FROM AUTHOR]

Influence of different levels of silicon under a variety of thermal treatment is investigated on the thermophysical behaviour of Al-Si-Cu-Mg automotive alloys. Conventional cast alloys are subjected to T6 heat treatment for age hardening. Hardness values, thermal conductivity along with microstructural observation under different heattreated conditions are well thought-out to comprehend the ageing performance and the precipitation behaviour of the alloys. From these investigational results it is indicated that two successive hardening peaks take place in the aged alloys. Ageing sequence consists of different phases like a supersaturated solid solution, GP zones, intermediate β", intermetallic β', equilibrium β and the Q phase but GP zones and the metastable phases are most likely responsible for these ageing peaks. Thermal conductivity decreases for these precipitates formation during ageing and increases for relieving the internal stress, dissolution of metastable phase and coarsening the precipitation of the alloys. Adding up of Si to the alloy showed earlier ageing peaks with higher intensities intended for its increasing properties of heterogeneous nucleation and diffusion kinetics. After ageing around at 200°C for four hours the alloys offer the height hardness. Microstructural study reveals that eutectic silicon makes the grain boundary coarsen and beyond the eutectic composition the star-shaped blocky primary Si is formed. Subsequent to ageing at 350oC for one hour the alloys reach completely recrystallized state. [ABSTRACT FROM AUTHOR]

The Al-Si-Mg alloy is highly popular in the aluminum industry, and the Mg2Si/Al composites demonstrate extensive development prospects. However, the practical production of these composites still faces certain obstacles. In this study, L32(49) orthogonal experiments were conducted to systematically examine the impact of heat treatment conditions on 15% Mg2Si/Al-8Si composites with 0.5%Sb modification. The microstructures of the as-cast alloys and heat-treated samples were studied using OM, XRD, DSC, SEM, EDS, and hardness tests. By conducting an orthogonal test, the influence of each factor was analyzed to quantify its magnitude and identify the optimal heat treatment process. The results showed that the hardness value of the alloy could be increased from 74.77 to 163.86 HV through heat treatment. Additionally, the average particle size of the initial Mg2Si could be refined from 19.15 to 12.44 µm. Furthermore, the hardening mechanism of the heat treatment parameters was discussed in detail. [ABSTRACT FROM AUTHOR]

AISI 52100 is a high carbon alloy steel typically used in bearings. One hardening heat treatment method for AISI 52100 is austempering, in which the steel is heated to above austenitizing temperature, cooled to just above martensite starting (Ms) temperature in quench media (typically molten salt), held at that temperature until the transformation to bainite is completed and then cooled further to room temperature. Different austempering temperatures and holding times will develop different bainite percentages in the steel and result in a variation in mechanical properties. In the present work, the bainitic transformation kinetics of AISI 52100 were investigated through experiments and simulation. Molten salt austempering trials of AISI 52100 were conducted at selected austempering temperatures and holding times. The microstructure of austempered samples were characterized with optical microscope and x-ray diffraction. The bainitic transformation kinetics were analyzed by Avrami equations using measured hardness data. The CHTE quench probe was used to measure the cooling curves in the molten salt from austenitizing temperature to the selected austempering temperatures. The heat transfer coefficient (HTC) was calculated with the measured cooling rates and used to calculate the bainitic transformation kinetics via DANTE software. The experimental results were compared with the calculated results and displayed good agreement. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is an additive manufacturing technique that can be used to make the near-net-shape metal parts. M2 is a high-speed steel widely used in cutting tools, which is due to its high hardness of this steel. Conventionally, the hardening heat treatment process, including quenching and tempering, is conducted to achieve the high hardness for M2 wrought parts. It was debated if the hardening is needed for additively manufactured M2 parts. In the present work, the M2 steel part is fabricated by SLM. It is found that the hardness of as-fabricated M2 SLM parts is much lower than the hardened M2 wrought parts. The characterization was conducted including x-ray diffraction, optical microscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy (EDS) to investigate the microstructure evolution of as-fabricated, quenched, and tempered M2 SLM part. The M2 wrought part was heat-treated simultaneously with the SLM part for comparison. It was found the hardness of M2 SLM part after heat treatment is increased and comparable to the wrought part. Both quenched and tempered M2 SLM and wrought parts have the same microstructure, while the size of the carbides in the wrought part is larger than that in the SLM part. [ABSTRACT FROM AUTHOR]

The research was aimed at investigating effective methods of surface strengthening of the working bodies of agricultural machines to increase their wear resistance and extend their service life. The study used surface hardening methods such as heat treatment, chemical and thermal processes, coatings, and mechanical methods. It has been shown that various methods of surface hardening significantly increase the wear resistance of working parts of agricultural machinery. The use of such heat treatment as induction hardening increased the resistance to wear due to localised heating and rapid cooling, which led to an increase in the hardness of the material. Chemical and heat treatment, including carburisation, nitrocementation and nitration, showed a significant improvement in surface layer hardness and increased corrosion resistance. Mechanical methods such as shot blasting and roller hardening have increased hardness and wear resistance by 30-50% due to plastic surface deformation. It has been proven that the use of surfacing and coatings of physical vapour deposition/chemical vapour deposition increases the durability of parts by 20-40%, which reduces operating costs and increases the productivity of agricultural machinery. The study examined approaches to enhancing the wear resistance of agricultural machinery's working parts, highlighting a notable issue: Ukrainian agricultural machinery often exhibits a shorter service life (1.2-2 times less) compared to imported counterparts. The analysis focuses on the reasons behind the wear and deterioration of cultivator teeth, with particular emphasis on how wear affects the size and shape of the working parts, resulting in decreased efficiency. The surface strengthening methods under study can be directly implemented in production to increase the durability and reliability of working parts of agricultural machinery, which would help to increase their efficiency and reduce operating costs. [ABSTRACT FROM AUTHOR]

Axle shafts, which are an important part of the vehicle's powertrain system, transfer the torque to the wheels and enable the vehicle to move. In this respect, the design of the axle shaft to be used in a new vehicle is of great importance for vehicle manufacturers. When a cylindrical shaft is torsionally loaded, the shear stress is highest at the surface of component and zero at the center. Therefore, these axle shafts are exposed to an induction hardening process that enables only this superficial case to have its properties changed, remaining the core zone with its material original characteristics. Current study presents the results of a project aimed at developing and evaluating the fatigue life of axle shaft that belongs to a commercial vehicle. Developments were made on the existing axle and the results were examined using experimental tests and finite element analysis method. In line with the improvements made, the developed axle shaft has 331.7% more fatigue life than the existing axle, while the cost is 24% lower. According to these results, more attention must be paid to material selection, induction hardening process, stress concentration and surface condition of axle shaft in the design. This study involves many disciplines such as design, manufacturing, analysis, testing, etc. It is very important to ensure communication between all these disciplines in the production of the product. The output obtained from one discipline becomes the input of another discipline. In the cumulative sum of all these inputs, the optimum level of parts is obtained. For this reason, this study, which processes all these disciplines together, is very valuable. [ABSTRACT FROM AUTHOR]

In recent years, there has been a notable increase in the frequency and intensity of natural disasters related to global warming. Large‐scale blackouts caused by natural disasters demonstrate the extreme vulnerability of power systems to these devastations. Resilience planning is the key to preparing power systems for natural disasters by enhancing the vital infrastructure's robustness. This paper proposes a new resilience improvement framework based on resiliency assessment and optimal hardening to improve the distribution system's resiliency against hurricanes. The main goal is to find the optimal distribution system line hardening solution according to reconfiguration potentials after the hurricane to minimize the distribution system cost of energy not supplied. Fragility curves and Monte Carlo simulations are used for the distribution system resilience assessment. Poles and conductors are vulnerable components of distribution system lines; therefore, two hardening strategies have been outlined using measures like replacing old poles with new poles, upgrading pole classes, and vegetation management. This method is modelled as an optimization program considering budget limitations and load priorities and implemented by a genetic algorithm on the IEEE 33‐bus standard network. The results show that optimal line hardening according to network reconfiguration potentials significantly increased the distribution system's resilience. [ABSTRACT FROM AUTHOR]

The effect of phase transformations on the steel/quenchant interfacial heat flux during quench hardening heat treatment is investigated in the present work. Experimental and modeling approaches comprising the inverse heat conduction problem (IHCP) were employed to analyze the thermal behavior of different steel grades with varying section thicknesses. The results revealed that phase transformation led to a distinctive pattern of the interfacial heat flux, characterized by a dip and subsequent rise. We observed that increasing the section thickness increases the surface heat flux for stainless steel probes without phase transformation. In contrast, the surface heat flux decreased with thicker sections in phase transformation. The increased heat evolved due to the latent heat liberation during phase transformation, and a reduction in thermal diffusivity due to increased specific heat caused a fall in the heat flow rates. Furthermore, the study proposed a phase transformation enthalpy parameter (ΔQ) to access the enthalpy change during quenching. ΔQ was consistent for a specific steel grade and independent of section thickness but varied with the cooling rate or quench media. The incorporation of phase transformation in the quenching heat transfer model is complex due to the required material data, including TTT/CCT diagrams and thermophysical properties that vary with steel grade. The study suggests directly incorporating the ΔQ values into the heat conduction equation or the IHCP model with phase transformation, simplifying the simulation process and minimizing data inputs. A database on ΔQ as a function of temperature and cooling rate would facilitate heat transfer modeling during quench hardening. [ABSTRACT FROM AUTHOR]

With the development of automotive lightweight technology, the improvement of the design of body sheet metal forming processes has gradually become a research focus. Advanced high--strength dual-phase steel is the main material for lightweight vehicle bodies, and exploring its accurate ductile fracture criteria plays an important role in predicting the forming fracture behavior of the sheet metal. The characterizations of the plastic behavior of the DP780 sheet before fracture were performed by the Swift hardening model. Three sets of tests from pure shear to tensile-shear stress states are designed to calibrate the ductile fracture parameters of Lou-Huh, Cockcroft-Latham, and Rice-Tracey criteria. The calibrated parameters are used to predict tensile shear test fractures and punching fractures at small bend fillets of molds. The results show the Lou-Huh criterion can accurately predict the shear fracture behavior of the DP780 sheet in the low-stress triaxiality (0.08-0.33). [ABSTRACT FROM AUTHOR]

The article aims to characterize Hadfield steel by analyzing its chemical composition, mechanical properties, and microstructure. The study focused on the twinning-induced work hardening of the alloy, which led to an increase in its hardness. The experimental data show that the material hardness at the surface improved considerably after solution heat treatment and work hardening, reaching more than 750 HV. By contrast, the hardness of the material core in the supersaturated condition was about 225 HV. The chemical and phase compositions of the material at the surface were compared with those of the core. The microstructural analysis of the steel revealed characteristic decarburization of the surface layer after solution heat treatment. The article also describes the effects of heat treatment on the properties and microstructure of Hadfield steel. The volumetric (qualitative) analysis of the computed tomography (CT) data of Hadfield steel subjected to heavy dynamic loading helped detect internal flaws, assess the material quality, and potentially prevent the structural failure or damage of the element tested. [ABSTRACT FROM AUTHOR]

It is shown that a set of production and mechanical properties of metastable β-titanium alloys make it possible to produce high-strength parts of a complex shape for aviation equipment. The influence of production regimes for manufacture and hardening heat treatment on structure and mechanical properties of thin-sheet rolled semi-finished products from metastable β-titanium alloy VT47 is studied. It is established that the degree of deformation during cold rolling of sheets due to occurrence of recrystallization processes upon heating to temperatures in the β-region does not significantly affect alloy mechanical properties in a heat treated condition. Varying the aging temperature makes it possible to control the combination of strength and ductility properties of VT47 alloy over a wide range. [ABSTRACT FROM AUTHOR]

[Display omitted] • The present study achieves a large-scale SNP dataset, a total of 512 genomes comprising 487 B. dorsalis and 25 B. carambolae. • B. dorsalis originates from the Southern India with three invasion routes worldwide, mainly facilitated by human activities. • CYP6a9 is identified that enhance the thermal adaptation of B. dorsalis and thus boost its invasion to temperate regions. • The gene function is further verified using the RNAi technology. The oriental fruit fly Bactrocera dorsalis is one of the most destructive agricultural pests worldwide, with highly debated species delimitation, origin, and global spread routes. Our study intended to (i) resolve the taxonomic uncertainties between B. dorsalis and B. carambolae , (ii) reveal the population structure and global invasion routes of B. dorsalis across Asia, Africa, and Oceania, and (iii) identify genomic regions that are responsible for the thermal adaptation of B. dorsalis. Based on a high-quality chromosome-level reference genome assembly, we explored the population relationship using a genome-scale single nucleotide polymorphism dataset generated from the resequencing data of 487 B. dorsalis genomes and 25 B. carambolae genomes. Genome-wide association studies and silencing using RNA interference were used to identify and verify the candidate genes associated with extreme thermal stress. We showed that B. dorsalis originates from the Southern India region with three independent invasion and spread routes worldwide: (i) from Northern India to Northern Southeast Asia, then to Southern Southeast Asia; (ii) from Northern India to Northern Southeast Asian, then to China and Hawaii; and (iii) from Southern India toward the African mainland, then to Madagascar, which is mainly facilitated by human activities including trade and immigration. Twenty-seven genes were identified by a genome-wide association study to be associated with 11 temperature bioclimatic variables. The Cyp6a9 gene may enhance the thermal adaptation of B. dorsalis and thus boost its invasion, which tended to be upregulated at a hardening temperature of 38 °C. Functional verification using RNA interference silencing against Cyp6a9 , led to the specific decrease in Cyp6a9 expression, reducing the survival rate of dsRNA-feeding larvae exposed to extreme thermal stress of 45 °C after heat hardening treatments in B. dorsalis. This study provides insights into the evolutionary history and genetic basis of temperature adaptation in B. dorsalis. [ABSTRACT FROM AUTHOR]

The article presents a model of non-hydration hardening of dispersed systems - mineral binders (without the stage of hydration) and the results of studies of gypsum stone with ash filler from the standpoint of the formation of the optimal structure of the material of non-hydration hardening, as well as its density and strength. The model assumes the use of binary mixtures of dispersed components with different dispersions. The study was based on data on the granulometric composition and dispersion of gypsum powders and aluminosilicate microspheres. It was isolated from the ash-slag mixture - waste from a thermal power plant. The aluminosilicate microsphere contains not only microsized spherical particles of the amorphous phase but also nanosized grains in a sufficient amount. This makes it possible to control the particle packing density. Experimental verification of the optimization of the granulometric composition of a binary dispersed system based on gypsum and ash microspheres was carried out. Based on the results, the optimal content of the filler in the composition of the non-hydration hardening structure was established. It is shown that filling with highly dispersed particles affects the performance properties of the resulting modified stone. [ABSTRACT FROM AUTHOR]

In this investigation, the specific cutting energy (SCE) and average surface roughness (Ra) were decreased using the hard-rotary turning (HRT) factors, including the inclined angle (I), depth of cut (D), feed rate (f), and spindle speed (S). The Bayesian regularized feed-forward neural network was applied to develop the SCE and Ra models. The entropy method and vibration and communication particle swarm optimization (VCPSO) algorithm were employed to compute the weights and determine optimal factors. The optimizing outcomes presented that the optimal I, D, f, and S were 35 deg., 0.45 mm, 0.50 mm/rev., and 1200 rpm, respectively, while the SCE and Ra were decreased by 37.4% and 6.6%, respectively. The total turning cost was saved by 7.5% at the selected solution. The valuable outcomes could be applied to the practical HRT process to decrease performance measures, while the developed HRT operation could be utilized for machining difficult-to-cut materials. [ABSTRACT FROM AUTHOR]

Laser transformation hardening (LTH) is the efficient method of surface hardening used for synthesizing a hard, wear resistant surface layer on parts through the ultrafast heating action of the high energy scanned laser beam. Initial microstructure plays a very significant role on nucleation and growth kinetics of austenite formation during ultrafast heating of laser treatment. The conventional hardening and tempering heat treatment can produce very interesting microstructure as initial microstructure for LTH. In this work the effect of the tempered structure as the initial structure on LTH 8620 steel was investigated. It was observed that initial tempered structure significantly affects the surface hardness and hardening depth after LTH. It was observed that microstructure containing more martensitic features and lesser carbides produces coarser martensitic structure with shallow hardened case depths. On the other hand, microstructure containing more ferritic structure and high-volume fraction of carbides showed finer martensite with deeper hardened case depths. LTH of all tempered specimens shows that with increase in tempering temperature surface hardness decreases. As compared to conventional hardening by quenching, it was observed that surface hardness increased by 52 to 128% for LTH. After LTH about 15 to 22% drop in surface hardness was observed with increase in tempering temperature for different scanning speeds. On the other hand, laser transformation hardened depth and laser transformation hardened width are observed to rise for all scanning velocities with tempering temperature. After LTH, laser transformation hardened depth is observed to increase by 18 to 24% whereas laser transformation hardened width is observed to rise by 12 to 43% when tempering temperature is raised from 205 to 705°C. [ABSTRACT FROM AUTHOR]

Case-hardening steels are gaining increasing interest in the field of laser powder bed fusion (PBF-LB/M) due to their excellent weldability. In combination with post-process carburization heat treatment, the surface properties can be improved to generate high-strength products. When manufacturing larger products by means of PBF-LB/M, the in situ heat accumulation and the altered cooling rates affect the resulting material properties. Therefore, the fabrication of larger products requires an understanding on the influencing factors that affect the material properties. This work investigates the effect of different volumetric energy densities (VED) on the resulting microstructural and mechanical properties. It is found that the hardness decreases continuously along the build direction. The gradient depends on the applied energy and is stronger for higher energy inputs due to heat accumulation and lowered cooling rates. Furthermore, countering strategies are investigated to avoid process-specific hardness reduction along the build direction. This includes a reduced number of parts within the build job as well as a modified inter-layer time (ILT) between consecutive layers of the specimen. Applying a moderate inter-layer time helps to counter process-specific overheating, which is indicated by an almost homogeneous material hardness and melt pool size along the build direction. [ABSTRACT FROM AUTHOR]

A model of the process which describes the dependence of the period accuracy of profiles with periodically recurring longitudinal corrugations on the ratio of the main diameters, height and cross-sectional dimensions of periodic corrugations is created; expressions for finding the optimum values of the main diameters, corrugations height and their cross-sectional dimensions that ensure minimum deviations of the longitudinal dimensions of profile periods from the nominal ones are obtained. The results of the researches carried out with the use of the method of mathematical planning of experiment are given. Practical recommendations on the use of the obtained results in designing the technology are prepared. As a result of the performed experimental studies of the influence of the main geometrical dimensions of molded corrugations - radii of their tops and bases, as well as height, analytical expressions for determining the optimal values of these parameters have been obtained, allowing to obtain finished profiles with minimum deviations in the lengths of periods, laid down in the design of technology in the calibrations of rolls. [ABSTRACT FROM AUTHOR]

The combined effects of concentration of chloride, carbon dioxide and thiosulfate on the oxide film formation and metal dissolution have been investigated for two cast duplex stainless steels, by electrochemical measurements. A comparative study was made between the alloys considering the effects of Cu addition in steel 1B. Different levels of hardness were obtained by solution treatment and aging at 450, 500, 550 and 600 °C for 1 h, in order to confirm the possibility of performing heat treatments capable of hardening the material, with minimal deleterious effects on corrosion resistance. According to the results, Cu improves the corrosion resistance in the media containing either NaCl only or CO2-saturated NaCl. Furthermore, the addition of thiosulfate to the CO2-saturated NaCl solution was beneficial for both steels, with a more pronounced effect for steel 3A. The effects on the localized and selective corrosion attack susceptibility were also investigated. [ABSTRACT FROM AUTHOR]

Alkali–silica reactivity (ASR) is one of multiple reactions responsible for premature loss in concrete infrastructure service life. ASR results in the formation of expansive, white-colored gel-like material which results in internal stresses within hardened concrete. ASR-induced stresses result in concrete cracking, spalling, and increased reinforcement steel corrosion rates. The main objective of this research is to improve the conditions of concrete infrastructure projects by mitigating ASR's damaging effect. The expansion of accelerated mortar bars poured using fine aggregates collected from different sources is measured versus time to evaluate the aggregates' reactivity. Different percentages of supplementary cementitious materials (SCMs), including class C fly ash and microsilica, were used in remixing mortar bars to evaluate the efficiency of different types of SCMs in mitigating mortar bar expansion. The research findings showed that SCMs can mitigate ASR, thus decreasing mortar bar expansion. The efficiency of SCMs in ASR mitigation is highly dependent on the incorporated SCM percentage and particle fineness. Silica fume, having the smallest particle size, displayed higher rates of ASR mitigation, followed by fly ash. The outcomes of this research will assist design engineers in avoiding future losses due to ASR cracking in concrete infrastructure projects, and reduce the excessive need for maintenance, repair, and replacement activities. [ABSTRACT FROM AUTHOR]

Purpose: Pulsed low-pressure carburizing (LPC) and omnidirectional high-pressure gas quenching (HPGQ) are innovative methods for quenching the surface layer. The thermochemical treatment carried out by this method reduces quenching geometric deformations, with detailed numerical values not available in the literature due to the short existence of this method. Design/methodology/approach: Sixteen toothed elements of EN 20MnCr5 steel were subjected to pulsed low-pressure carburising with omnidirectional jet quenching in 4 groups, varying the process temperature (920°C, 960°C) and in two groups performing a tempering treatment. The elements were tested before machining by measuring their internal hole diameters, radial runout, roundness and cylindricity. These values were tested again after treatment. The direction of change and the statistical significance of the effect of treatment and its parameters, temperature and tempering were analysed. Findings: Thermo-chemical treatment significantly affects geometric changes in diameters, roundness, cylindricity and radial runout compared to elements without heat treatment due to physical transformations occurring during this treatment (p<0.05). Changing the process temperature in the value range of 920°C-960°C affects the hole diameter (makes it smaller) (p<0.05), but does not affect radial runout, cylindricity and roundness. The observed dimensional changes in diameters have numerically small values (<0.005 mm). The tempering treatment can affect the values of average diameters. Its effect on roundness, cylindricity and radial runout was not observed. Research limitations/implications: In the temperature range studied, the method of pulsed low-pressure carburising + omnidirectional high-pressure gas quenching makes it possible to raise the temperature of the process and shorten its duration without significant geometric changes in the treated elements. Practical implications: The method of pulsed low-pressure carburising and omnidirectional high-pressure gas quenching (HPGQ) ensures the maintenance of reproducible quenching deformations at a level significantly lower than conventional processing methods. Originality/value: The method of pulsed low-pressure carburising together with omnidirectional high-pressure gas quenching (HPGQ) is a method that has been used briefly in the industry, and there are few reports on it to date. [ABSTRACT FROM AUTHOR]

Taking into account the numerous previous attempts to use waste glass for concrete production, an approach was proposed based solely on car side window glass waste. Only side window waste emerging during the production of car side windows was used during the research program. In this way, all key properties of the waste glass were under control (purity, granulometric properties, etc.). Two types of concretes with crushed side window glass, playing the role of coarse aggregate, were created. Concretes were differentiated by the amount of added crushed side window glass, which replaced 10-50% of the natural aggregate. Created concretes were thoroughly tested in the state of both a fresh mix and hardened composite. Consistency and air content of fresh mixes were tested. Slump was ranging from 15 mm to 20 mm and air content was ranging from 2.5% to 3.1%. Hardened composites were used to test apparent density, compressive strength, water absorption, water-tightness and resistance to freeze-thaw cycles. It was proven that concrete with side window glass as partial aggregate substitution is characterized by satisfactory mechanical properties (compressive strength after 28 days of curing was ranging from 51.9 MPa to 54.7 MPa), enabling its application as ordinary structural concrete. Properties of both fresh concrete mixes and hardened concretes based on crushed side window glass are similar to a reference concrete. It was proved that it is possible to replace up to 50% of natural coarse aggregate by crushed side window glass. Possible applications of the concretes in question were proposed. Experience gained during the research program is likely to be useful for tests of using crushed side window glass sourced from decommissioned cars and trucks. Areas where future research is needed are indicated. [ABSTRACT FROM AUTHOR]

A study of the properties of industrial sheets made of alloy 1580, including the determination of mechanical properties for tensile strength, impact strength, manufacturability during machining and shape- changing operations of sheet stamping, as well as during welding, has been carried out. The comparison of technological properties of alloy 1580 sheets with the properties of sheets made of aluminum alloy 1560, 1160, and 1201 has been performed. It has been established that alloy 1580 and 1560 sheets have similar properties in terms of machinability, manufacturability during shape-changing operations of sheet stamping, and weldability by electron beam welding. It is shown that the characteristics of the alloy 1580 during machining and shaping during sheet stamping are generally close to those of alloys 1160, 1201, and the absence of the need for hardening heat treatment (quenching followed by aging) and the high isotropy of the properties of semi-finished products are the advantages of the alloy 1580. The conducted studies indicate the prospects of using sheet semi-finished products of alloy 1580 for the manufacture of critical parts in various fields of mechanical engineering, such as aviation, space industry, automotive construction and shipbuilding. [ABSTRACT FROM AUTHOR]

This paper deals with analysis and comparison of the equivalent plastic strain and temperature fields in the aluminium alloy 2024 T3 (AA2024 T3) welded joint, with macro/microstructure appearance and hardness profile. In the alloys hardened by heat treatment, grain size and particle size of the precipitate are functions of equivalent plastic strain, strain rate and temperature. By analysing the equivalent plastic strain fields and temperature fields it is possible, to some extent, to capture the effect of welding parameters and thermo-mechanical conditions on grain structure, and therefore hardness and strength in the welded joint. A coupled thermo-mechanical model is applied to study the material behaviour during the linear welding stage of friction stir welding. The 3-D finite element model has been created in ABAQUS/EXPLICIT software using the Johnson-Cook material law. The values of thermo-mechanical quantities during the welding stage are obtained from the numerical model and shown as distributions across the joint. The obtained values of these quantities are related to the microstructure of the joint zones and hardness distribution, and this relation is discussed. [ABSTRACT FROM AUTHOR]

Currently, a large number of studies are being conducted in the field of application of methods of thermal and chemical-thermal treatment, and there are some unresolved technological problems. In particular, the issues of the formation of wear-resistant structures have not been sufficiently studied in the study of combined methods of chemical and thermal treatment, the development of which makes it possible to reduce the technological cycles of the hardening process of the surface layer of metals. This paper examines the issues of the formation of wear-resistant structures during technological operations that allow combining the tempering process with the saturation of the steel surface with nitrogen and carbon atoms, as well as issues of reducing the technological cycles of hardening using methods of chemical-thermal treatment, the possibility of using standard equipment, preparation of the saturation medium based on local raw materials. [ABSTRACT FROM AUTHOR]

The article discusses the results of research work on an innovative technology for the manufacture of carbide blades for metal-machining tools from ultrafine tungsten powders. Analysis of the results of the study showed that the shape and dimensions, the level of residual internal stress in the cutting part of the machining tools, as well as the granulometric composition of tungsten powders affect the resistance of carbide plates. In the studies carried out, special attention was paid to the study of the stress state of the working elements. The stress state of an insert made of a hard alloy (five-fold difference in thermal expansion coefficients) and a molybdenum alloy (three-fold difference in thermal expansion coefficients) steel 40XNML leads to the creation of a state of all-round compression in the insert upon cooling. [ABSTRACT FROM AUTHOR]

The present investigation focuses on the effect of heat treatment parameters on the hardening and fracture behavior of 17-4 PH stainless steel, thereby assessing the susceptibility to failure at intense loading conditions. The tensile tests were conducted at an effective strain rate of 47 s−1 on a GleebleTM 3800 thermo-mechanical simulator at room temperature and 75 °C. X-ray diffraction (XRD) analyses revealed the presence of a predominant martensitic phase with significant reverted austenite content at higher aging times in the 480 °C condition, thereby resulting in the softening phenomenon and lower strength values. Peak hardness and superior strength values were obtained for higher aging times in the 450 °C condition and lower aging times in the 480 °C condition due to precipitate-particle segregation at packet junctions and finer lath microstructure. Consequently, the fractographic observations from scanning electron microscopy (SEM) exhibited a semi-brittle mode of failure. In the over-aged conditions, a transition toward ductile fracture mode with dimple morphology was depicted. The higher testing temperature produced a uniform set of failure strain values compared to the scattered strains at ambient conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The aging hardening behavior of the Mg-Sm-Nd-Zn-Zr alloy was clarified. • The precipitation evolution of the Mg-Sm-Nd-Zn-Zr alloy was revealed. • The intrinsic relationship between hardness and precipitates is established. Precipitation-hardenable Mg-Sm-Nd-Zn-Zr alloy is a high-performance magnesium alloy with great potential for aviation applications. A more comprehensive understanding of the precipitation evolution will help fully exert its mechanical properties. The hardness initially rose and then fell with alloy aging to 100 h at 200 °C. A peak hardness of 84.1 HV was achieved at the aging time of 20 h, with a 39.7 % increase in hardness compared to the unaged alloy. The primary precipitates were the GP zones and β′ phase at the under-aged stage. As the aging time was extended to 20 h, a more abundant β′ phase precipitated in the matrix, and the alloy achieved the peak-aged stage. Eventually, the over-aging stage came with the aging process continuing, where the β′ phase coarsened severely and further transformed into the β 1 phase. When the aging temperature was raised to 350 °C, even under a short aging time of 1 h, the coarse β 1 phase formed rapidly, and the β phase could also nucleate and grow directly on the β 1 phase. This work offers a guide for developing aging treatment processes for Mg-RE alloys. [ABSTRACT FROM AUTHOR]

The mechanisms that govern a previously unexplained hardening effect of a single phase Cu-30wt%Zn α -brass after heating have been investigated. After cold-work, the alloy possesses an increased yield strength and hardening rate only when heat treated to temperatures close to 220 °C, and is otherwise softer. Crystallographic texture and microstructure, explored using electron backscatter diffraction (EBSD), describe the deformation heterogeneity including twin development, as a function of the heat treatment conditions. When heated, an increased area fraction of deformation twins is observed, with dimensions reaching a critical size that maximises the resistance to dislocation slip in the parent grains. The effect is shown to dominate over other alloy characteristics including short range order, giving serrated yielding during tensile testing which is mostly eliminated after heating. In-situ X-ray diffraction during tensile testing corroborates these findings; dislocation-related line broadening and lattice strain development between as-worked and heated α -brass is directly related to the interaction between the dislocations and the population of deformation twins. The experiments unambiguously disprove that other thermally-induced microstructure features contribute to thermal hardening. Specifically, the presence of recrystallised grains or second phases do not play a role. As these heat treatments match annealing conditions subjected to α -brass during deformation-related manufacturing processes, the results here are considered critical to understand, predict and exploit, where appropriate, any beneficial process-induced structural behaviour. [Display omitted] [ABSTRACT FROM AUTHOR]

The research presented in this article aimed to obtain a semi-finished product in the form of TRIP wires, which in further research will be used to produce fasteners in the form of KPS-6 screws used in the construction industry. At present, the process of manufacturing this type of fastener (from wire rod to the finished product) involves two technological lines: one for carrying out the drawing process and obtaining a semi-finished product in the form of a wire with appropriate properties, and the other for the production of fasteners. Semi-finished product wires with a ferritic-perlitic structure obtained after the drawing process are the starting product for the production of fasteners, the tensile strength of which is approximately 450 MPa. In order to be able to obtain fasteners characterized by an increased level of properties in 8.8 grade, after the screw manufacturing process, heat treatment should be carried out by hardening and tempering. The new technology proposed in the article includes: a drawing wire rod with a semi-finished product diameter, two-stage heat treatment on the line for pass-through heating and cooling, ensuring the obtaining of a TRIP-type structure in drawn wires, and calibration drawing. The product of this process was a wire whose tensile strength was in the range of 700–800 MPa with a TRIP structure. Thanks to obtaining a TRIP-type structure with the assumed amount of retained austenite, we obtained wires with higher strength properties and very high plasticity in relation to wires with the same chemical composition and ferritic and perlitic structure. The research carried out in the article also allowed us to obtain, in the semi-finished product wires, a favourable relationship between the strength properties and plasticity of the material, expressed by the value of the Re/Rm coefficient (yield strength/tensile strength) and the so-called yield ratio, which determines the material′s susceptibility to cold deformation; the smaller these coefficients, the greater the yield strength. The subsequent stages of the research will include the development of forming fasteners in the form of KPS-6 screws used in the steel construction industry with TRIP structures, with increased properties of products in the 8.8 property class, without conducting heat treatment by hardening and tempering. It is assumed that the resulting product will have an additional usable feature: preserving a certain amount of retained austenite in the structure of the finished fasteners, which will be transformed into martensite during operation, and thus affect the longevity of the fasteners. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V is the largest useable titanium grade alloy in various engineering components due to its superior inherent properties like high strength to weight ratio, highly corrosive resistance, ability to withstand high temperature, etc. But machining of this alloy is found to be challenging because of having lesser thermal conductivity, highly chemical sensible, more sensitivity in work hardening and low young's modulus. However, the current study offers the use of novel and environment pleasant lubricants like iron aluminium oil with minimum quantity lubrication (MQL) concept to machine this alloy using a low budget hard tool (uncoated carbide) and the performance was compared with dry machining. Severe abrasion, adhesion, diffusion, and chipping were the main cause of tool failure in both cooling strategies. The tool life in MQL was traced to be 280% greater than the dry condition at the same turning parameters. Compared to dry turning, lower tool vibration and superior surface quality were obtained in MQL. The MQL assisted turning exhibited 12.38% lower costs than dry. Overall, with the use of an uncoated carbide tool, the turning of Ti-6Al-4V alloy in MQL was found to be more precise and more economical than dry and recommended for mass production works. [ABSTRACT FROM AUTHOR]

Ultrafine grained (UFG) metallic materials obtained by severe plastic deformation (SPD) typically exhibit very high strength properties, whose values are much higher than those predicted by the well-known Hall–Petch relation. Our studies show that the basis for this to occur is that SPD not only forms the UFG structure, but also leads to the formation of other nanostructural features, such as dislocation substructures, nanotwins, and nanosized precipitates of second phases, which additionally contribute to strengthening of materials. At the same time, this analysis of hardening mechanisms indicates that the structure and condition of grain boundaries, namely, their nonequilibrium state and the presence of grain boundary segregations, also substantially contribute to hardening. Taking this into consideration, approaches are discussed to achieve very high strengths in metallic materials by SPD. [ABSTRACT FROM AUTHOR]

CrN coatings are widely used in the industry due to their excellent mechanical features and outstanding wear and corrosion resistance. Using scratch and ball-on-disk wear tests, the current study deals with the tribological characterisation of CrN coatings deposited onto an X42Cr13 plastic mould tool steel. Two surface conditions of the secondary-hardened substrate are compared—the plasma nitrided (duplex treated) and the un-nitrided (simply coated) states. The appropriate combination of secondary hardening providing the maximum toughness and the high-temperature nitriding of this high Cr steel is a great challenge due to the nitrogen-diffusion-inhibiting effect of Cr. The beneficial effect of the applied duplex treatment is proven by the 34% improvement of the adhesion strength and the 43% lower wear rate of the investigated duplex coatings. Detailed morphological analyses give insight into the characteristic damage mechanisms controlling the coating failure processes during scratching and wearing. For the simply CrN-coated sample, a new type of scratch damage mechanism, named "SAS-wings", is identified, providing useful information in predicting the final failure of the coating. The tribological results obtained on tribosystems with the investigated high Cr steel/CrN constituents represent a novelty in the given field. [ABSTRACT FROM AUTHOR]

Complex structures can now be manufactured easily utilizing AM technologies to meet the pre-requisite objectives such as reduced part numbers, greater functionality, and lightweight, among others. Polymers, metals, and ceramics are the few materials that can be used in AM technology, but metallic materials (Magnesium and Aluminum) are attracting more attention from the research and industrial point of view. Understanding the role processing parameters of laser-based additive manufacturing is critical to maximize the usage of material in forming the product geometry. LPBF (Laser powder-based fusion) method is regarded as a potent and effective additive manufacturing technique for creating intricate 3D forms/parts with high levels of precision and reproducibility together with acceptable metallurgical characteristics. While dealing with LBPF, some degree of porosity is acceptable because it is unavoidable; hot ripping and cracking must be avoided, though. The necessary manufacturing of pre-alloyed powder and ductility remains to be the primary concern while dealing with a laser-based additive manufacturing approach. The presence of the Al-Si eutectic phase in AlSi10Mg and AlSi12 alloy attributing to excellent castability and low shrinkage, attaining the most attention in the laser-based approach. Related studies with these alloys along with precipitation hardening and heat treatment processing were discussed. The Pure Mg, Mg-Al alloy, Mg-RE alloy, and Mg-Zn alloy along with the mechanical characteristics, electrochemical durability, and biocompatibility of Mg-based material have been elaborated in the work-study. The review article also summarizes the processing parameters of the additive manufacturing powder-based approach relating to different Mg-based alloys. For future aspects, the optimization of processing parameters, composition of the alloy, and quality of powder material used will significantly improve the ductility of additively manufactured Mg alloy by the LPBF approach. Other than that, the recycling of Mg-alloy powder hasn't been investigated yet. Meanwhile, the post-processing approach, including a homogeneous coating on the porous scaffolds, will mark the suitability in terms of future advancements in Mg and Al-based alloys. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the production of building reinforcing steel, special charge components were used, consisting of steel waste, cast iron shavings and about 20 % of NVG pellets. Steel was smelted in a 60-ton electric arc furnace. The pouring of liquid steel was carried out on a continuous casting machine. Heat treatment was carried out immediately after the rolling operation to improve the physical and mechanical properties of the construction reinforcing steels melted in the electric arc furnace from the charge material using metal waste. It is recommended that these steels be made of low-carbon (C≤0.25 %) and low-alloy steels in order to have a sufficiently high technology and good weldability. However, in order to meet the requirements of construction standards, these steels must have high structural integrity and physical and mechanical properties. It was found that these requirements can be solved only by heat treatment immediately after the rolling operation of the armature. In this case, the effect can be obtained by reinforcing heat treatment of the fittings by hardening due to the rolling temperature. Therefore, in order to further improve the properties during thermomechanical treatment (TMT), the hardening was carried out directly (immediately) after the deformation in the roll. Immediately after the spread, the physical and mechanical properties, as well as the fluidity and strength properties of the construction low-carbon reinforcement steels met the requirements of the standard by conducting HTMT. Increased strength and technological properties of reinforcing steel are achieved after hardening by dispersion hardening at high-temperature tempering, which is carried out at a temperature of more than 580 °C. [ABSTRACT FROM AUTHOR]

As a subset of the PMP-HSDE program, CU Boulder will offer certificate programs tailored to specific design skills and tools. The ten-course master's program will integrate the Ansys Electronics Desktop Student software product, which students can easily download to access Ansys HFSS, Ansys Maxwell, Ansys Q3D Extractor, and Ansys Icepak. The University of Colorado Boulder will launch a master's degree program that will integrate and feature Ansys' best-in-class electronics simulation in its new Professional Master's Program in high-speed digital engineering. [Extracted from the article]