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The chip study can be the simile to the biopsy in the machining process, as it exposes physical phenomena that are generated in the machining process (heat transfer, hardening, phase changes, heat treatments, etc.). These physical phenomena are directly influenced by the cutting parameters applied to the process (feed, cutting speed, and depth). A chip analysis procedure is proposed to estimate some of the physical phenomena generated in the micro-end-milling in a conventional CNC machine on 7075 aluminium and Ti-6Al-4 V titanium alloys. The procedure is composed of hardness tests, metallography, scanning electron microscopy (SEM), and infrared thermography. A softened chip is observed in the Ti-6Al-4 V titanium a hardened one in 7075 aluminium alloy. The chip approach evaluation evidences a great variation regarded to thermal characteristics between micro-machining and meso-machining focused on the scale of the removed layer thickness.

Aluminium hybrid functionally graded metal matrix composites (FGMMCs), meet growing demands for supreme tribo-mechanical performance in automotive and aviation industry. This research experimentally compares the influence of carbide ceramics (B4C, SiC, TiC) as reinforcements, in improving reciprocating tribology performance and mechanical strength of A333 hybrid composites against alloy. Hollow cylindrical samples of A333/6 wt%B4C/4 wt%TiC and A333/6 wt%B4C/4 wt%SiC hybrid FGMMCs were developed using horizontal centrifugal casting. Metallography analysis on both composites revealed increasing ceramic gradient distribution towards outer composite wall. Particle rich zone of A333/B4C/SiC hybrid FGMMC showed maximum micro-hardness (198.9 HV) and tensile strength (267.9 MPa). Elemental mapping confirmed effective distribution of ceramics and detected elemental composition of both composites. Particle rich layer of A333/B4C/SiC hybrid FGMMC exhibited improved wear resistance in comparison with all three layers of A333/B4C/TiC hybrid FGMMC and alloy. Third-body abrasion and tribo-chemical wear were the predominant mechanisms revealed for both composites during worn surface analysis.

Hexagonal boron nitride (h-BN) fillers are incorporated into poly(vinyl butyral) (PVB) coatings to improve the corrosion protection performance of copper. It has been revealed that the h-BN fillers exhibit an excellent dispersiblility in PVB coating due to the non-covalent interactions between h-BN fillers and the PVB molecules. Electrochemical characterization reveals that the corrosion resistance of the BN-reinforced PVB (BN-P) coating is 5–6 orders of magnitude higher than that of the pristine PVB coating. Photographs and metallography show that the copper substrate beneath the BN-P coating does not suffer from corrosion after immersion for 2 months, indicating that the BN-P coating can provide a long-term protective barrier for the underlying copper substrate. Loading 0~0.25 g h-BN fillers in 2.0 g PVB, the corrosion protection performance increases with increasing the loading of h-BN fillers. The scratch test results suggest that h-BN fillers do not accelerate copper corrosion when the BN-P coating is damaged.

A metallurgical and technological characterization of a seventh century seax coming from the Lombard necropolis of Campo San Giovanni in Leno (Brescia, northern Italy) was carried out to investigate the smithing technology involved in the blade manufacturing process. At first, a metric-based typological investigation of the seax was performed. X-ray radiography was used to gain a preliminary non-destructive technological assessment of the object. Optical microscopy and Vickers hardness measurements have allowed a metallurgical and mechanical characterization of the metal matrix both at the upper and lower blade portion. The results show that the seax blade was forged using different steel bars and also hypereutectoid steel. In addition, a selective quenching was performed by the ancient blacksmith to enhance the cutting-edge hardness. Scanning electron microscopy coupled with X-ray dispersive spectroscopy was employed to determine the chemistry of a large sample of nonmetallic inclusions entrapped within the metal matrix. A multivariate statistical analysis of the inclusions compositional data was used to carefully examine the composite nature of the artefact and trace the origin of the seax steel.

Friction extrusion is a thermomechanical process that combines conventional extrusion with the action of a rotating die. The plastic deformation of the material being sheared and extruded is the primary source of process heat and it produces strain distributions unlike those resulting from conventional extrusion. This paper proposes an improved strain analysis that evaluates three main strain components in a series of rate-controlled friction extrusions in which the steady state was achieved. Cylindrical AA1100 extrusion billets with two embedded markers were extruded to wire with a 10:1 diametral reduction. The shape change of the embedded markers was determined via serial, transverse sectioning and quantitative metallography of the extruded wires. Three mutually orthogonal strain components (longitudinal, circumferential, and radial) were calculated at different positions along each extruded wire from the marker's shape change. The development of strain from the initial transient to the steady state is discussed. The variation of the steady-state strain with different process parameters is correlated with the die advance per revolution.

The authors have studied the effect of alloying on the structure, microhardness and abrasive wear resistance of electroslag surfacing layers on low-alloy structural steel 09G2S. For modification, mixtures of Si3 N4 + FeSi2 + Si powders obtained in the Department of Structural Macrokinetics of the Tomsk Scientific Centre SB RAS by the method of SHS synthesis, as well as powder compositions based on TiC, were used. A molten electrode was made of low-alloy steel St3, on which modifying compositions Si3 N4 + FeSi2 + Si were poured out, in the first case, and modifying compositions Si3 N4 + FeSi2 + Si, located below, in the second case. Metallography and X-ray microanalysis methods were used to determine the structure and to analyze the composition of the deposited layers, heat-affected zone (HAZ) and the base metal, on the basis of which assumptions were made about the nature of the formation of coating properties – hardness and wear resistance. It is shown that the main influence on the wear resistance is exerted by structure of the surfacing metal. There is a positive effect of modifying coatings by alloying materials with the alloys Si3 N4 + FeSi2 + Si + St3 and TiC + St3. In the molten layer, many new crystallization centers are released in the form of dispersed TiC particles. Dispersed TiC particles with a high melting point (3180 °C) are the first to fall out of the melt and not only serve as multiple crystallization centers, but also prevent the growth of austenitic grains, which ensures the formation of dispersed structure. The coatings contain TiC carbide particles, as well as inclusions of other phases. At the same time, an increase in hardness of the deposited layer containing titanium carbide inclusions is observed in direction of the boundary with the base. Wear resistance of the layer increases when a TiC-based coating is formed. The obtained data can be used to create deposited layers on the metal surface with high resistance against abrasive wear.

The gas produced from an oil field is used to inject into the well for enhanced recovery of oil and gas. The injected gas flows through a pipeline called a header to individual wells for gas injection. One such 6” gas injection header at an offshore process complex experienced a leakage during operation just after 2 years of service. The operating pressure of the pipeline was normal, and there was no process disturbance at the time of the failure. There was no localized corrosion and thinning of the header. The material of construction of the header sample was reported to be ASTM A106 Gr B specification. Laboratory investigations revealed that the material did not conform to ASTM A106 Grade B standard. In the present case, the H2S partial pressure was 0.09 psi; this comes under sulfide stress cracking (SSC) region 2 as per ISO 15156-2:2015; therefore, the environment is prone to SSC. During metallography and SEM analysis, cracks filled with corrosion product typical of SSC were observed which propagated intergranularly. Zigzag cracks typical of hydrogen-induced cracking that branched out from the main SSC crack were also observed. As the metal was too brittle in nature, the gas injection header cracked at many sites. When the crack grew to the extent that the pipe could not withstand the operating pressure anymore, it failed in a brittle manner and the header was shattered into pieces.

The effect of the conditions and temperature of static tensile deformation on the mechanical properties and structure of a high-temperature KKh28M6 cobalt alloy (Co–Cr–Mo system) prepared by selective laser melting is studied. An effect of the loading conditions at temperatures of 900–1100°C on the ultimate tensile strength of the alloy is revealed.

The embrittlement resistance of the claddings made of an E110 zirconium alloy of various degrees of purity under high-temperature oxidation conditions close to the LOCA conditions is estimated using a developed technique, which includes the determination of static fracture toughness, quantitative metallography, and electron-probe microanalysis. This technique demonstrates that the alloy based on a zirconium sponge has the best fracture toughness and the Zr–1% Nb–0.13% O–0.12% Fe alloy has the minimum fracture toughness.

The relationship between as-cast and post-friction-stir-processed microstructures was assessed by a combination of quantitative metallography and statistical analysis. Two distinct as-cast microstructures, resulting from commercial and continuous casting processes, were subjected to multiple friction stir passes and subsequent metallography by SEM with EDS. X-ray maps were used to elucidate Si particles for quantitative image processing. Progressive homogenization with each successive pass was observed in both alloys. Continuously cast samples exhibited Si particle coarsening, while commercially cast alloys undergo Si particle refinement. Aspect ratio of particles remains constant throughout multiple FSP passes despite changes in spatial and particle size distribution. Trends in distributions of Si particle size and nearest neighbor distances with each pass are presented.

Joining SiALON to duplex stainless steel utilizes the properties of two materials which may provide an opportunity for distinctive applications. Ceramic is hard and operates at a high temperature but it is brittle whereas metal is tough but it can work at a low temperature. The benefits of the best properties of both materials can be utilized by joining them. The objectives of the research work are to investigate the physical properties and the phase transformation at the interface and at the inter-diffusion layer in between the SiAlON and duplex stainless steel. The experiment incorporated nitriding, then diffusion bonding the duplex stainless steel using the hot press. Bonding was carried out at 1200°C for the holding times of 30 minutes and 1 hour. Metallography and micro analyses were conducted to achieve the above objectives. The study has demonstrated that 30 minutes joining time is sufficient to develop the thickness of the interface. However, 1 hour joining duration achieved cohesive and sound diffusion bonding of the SiAlON to duplex stainless steel. This is possible due to the formation of diffusion interlayer which accommodates the residual stress presence during cooling down process.

Directed energy deposition (DED) is an Additive Manufacturing process deposing fused metal powder on a preexisting substrate. This document shows the influence of heat treatment on P295GH deposit made by DED, for hybridization process. The heat treatment must reduce the macroscopic differences between the rolled substrate and the deposited DED material. The experimental plan has been defined around AC3 temperature, according to P295GH existing literature. XRD analysis, hardness measurements and metallographic inspections have been performed on samples before and after heat treatment. XRD analysis and hardness measurements have shown an isotropic material. The as-built microstructure is ferritic and acicular, but coarsens after the heat treatment. The study promotes a heat treatment at 800°C during 3 hours to obtain the best compromise between properties, impact on the substrate and differences with the rolled substrate.

The article is devoted to a comprehensive analysis of the coating of a component from the Ford Fo-cus 1.0 l EcoBoost engine. It is one of a pair of materially identical aluminum gears connected by a drive pulley and a drive. Aluminum gear components are surface treated with a mixture of metal powders using PVD technology, where the goal of the coating is to increase the hardness, abrasion resistance and heat of the base material. The chemical composition of the basic material of the gea-red aluminum drive wheel of the FORD engine proves that it is a component made by thermofor-ming and corresponds to the alloy EN AW 6061 (AlMg1SiCu) according to the standard CSN EN 573 1-3. The microstructure of the base material component exhibits fine intermetallic phases evenly dis-tributed throughout the cross-section of the base base material, without the occurrence of larger inc-lusions and/or porosity. The cross-sectional microstructure in the area of the coating demonstrates that the component has a continuous uniform surface layer of the coating formed without a defect and does not have a diffuse bond with the base material. The measurement of the coating thickness of the component shows a continuous surface layer formed by powder metallography, which ranges from 70.1 µm to 143.9 µm. The surface EDS of the surface proves that it consists of deposited tungsten carbides produced by powder metallography and the bonding material is cobalt. Area EDS analysis of the surface coating identified morphologically two distinct areas of dark and light, where tungsten carbides and cobalt are based, and only the tungsten carbide and cobalt carbide contents change. The oxygen and carbon content also changes in the dark and light areas.

The present paper provides a solution to enhance the reliability of bonding. The effect of the nonwoven carbon tissue (NWCT) composite adhesive layer on the bonding strength and reliability of aluminum alloy of single lap joints (SLJ) was investigated by embedding NWCT into the epoxy adhesive layer. The bonding strength, Weibull distribution, metallography of cross section, and fracture surface morphology of NWCT specimens were investigated. The results showed that the average bonding strength and Weibull characteristic strength (WCS) of NWCT-reinforced specimen were 16.78 and 17.17 MPa, which increased by 70.2 and 66.7%, respectively, compared with the neat specimen, and the Weibull modulus increased from 11.46 to 22.83, which indicated that NWCT specimens had higher bonding reliability. The mechanism of microcrack formation was obtained by analyzing the cross section of specimen loaded 95% WCS without macroscopic damage. The metallographic section showed that the microcrack of the neat specimen originated from the adhesive-aluminum interface, while the microcracks of the NWCT specimen originated from the interface between short carbon fibers (SCF) and adhesive. Typical failure modes were gained from visual observation and SEM. The failure mode of the neat specimen included more Al-adhesive interface failure, while the NWCT specimen included more internal failure of adhesive-SCFs with the fracture, pullout, peeling, and slippage of SCFs improving the toughness and bonding strength of the adhesive layer. The bridging effect of SCFs in the adhesive layer reinforced by NWCT can even the load and release the stress to improve the bonding reliability.

Quantitative percussion diagnostics (QPD) is a non-destructive evaluation method that has been used successfully in a number of applications. This technique involves a rod that is actuated to impact a specimen with a given amount of kinetic energy and the resulting mechanical response of the specimen as a function of time is measured using a piezoelectric force sensor. The mechanical energy returned to the rod is then analyzed. Because contact with the specimen is on the order of a few hundred microseconds, QPD can be used in situations and for specimen conditions (e.g. high temperature) that are not feasible for other nondestructive testing methods. The objective of the present study was to evaluate the use of QPD for characterization of defects in specimens fabricated using two additive manufacturing methods, i.e. cold spray deposition and laser powder directed energy deposition (LPDED). Cold spray specimens were produced using commercially pure nickel with varied process conditions including gas type (i.e. helium and nitrogen) and deposition rate. In addition, a Ti–6Al–4V specimen was manufactured using LPDED with varying porosity content. All specimens were characterized using both QPD and destructive methods (i.e. cross-sectional metallography) to compare results for observed defect characteristics. Cold spray specimens exhibited a lower energy return when they contained more porosity and/or surface roughness. Microscopic plastic deformation at highly porous surfaces was indicated during percussion testing that reached a saturation level after repeated percussion. Overall, the results showed that QPD can effectively evaluate cold spray and LPDED specimens for porosity and surface roughness.

The manifestations of ancient metals’ embrittlement, cracking and fracture, are challenging problems for restorers and conservators, yet the scientific understanding of these problems is limited. In particular, the study and interpretation of fracture surfaces, fractography, is a minor or non-existent consideration for most archaeometallurgical investigations. This paper presents a survey of fractographic analyses, in combination with the more widely used disciplines of microstructural studies, metallography, and chemical analyses for some Old-World copper alloy (bronzes) and high-silver alloy artifacts that have undergone long-term corrosion and embrittlement damage. We show that fractography, as an adjunct to metallography, can improve the interpretation of these types of damage and assist in selecting the best methods for restoration and conservation of the objects made from these alloys.

The object of research is hard alloys with a morphology of the carbide phase skeleton structure, in which particles contact with each other, and the gaps between them are filled with a binder phase. The mechanical and service characteristics of such materials depend on the degree of development of the skeleton structure. One of the most problematic areas is the lack of non-destructive methods for determining the parameters of the structure. The introduction of such techniques will allow obtaining objective information on the structure of the material and using it to evaluate the quality of products. In the course of the study, the parameters of the scattering of elastic vibrations in inhomogeneous media were determined. The main hypothesis of the study is the assumption that the processes of energy dissipation occur both in the structural elements themselves (carbide grains and bond areas) and at their boundaries. Therefore, the evaluation of dissipation processes will allow obtaining a quantitative estimation of the alloys structure parameters, and will allow assessing the quality of the material. The following characteristics were chosen as the parameters characterizing the propagation of ultrasonic oscillations: the speed of the oscillations propagation, the scattering background level in relation to the amplitude of the bottom reflection, the oscillations attenuation coefficient. The parameters were determined and compared with the characteristics of the quality of the products and the parameters of the microstructure, which were determined by the methods of quantitative metallography and the statistical characteristics of the relationship between the parameters, were determined. As a result, new quality control procedures for carbide products have been developed. The contiguity characteristics of the carbide skeleton of the sintered cemented carbide were determined by measuring the propagation speed of ultrasonic oscillations. The assessment of the level of porosity with a pore size of less than 1 mm was carried out according to the results of measuring the relative amplitude of the background scattering of ultrasonic oscillations. The proposed methods are non-destructive and are carried out in one cycle with ultrasonic flaw detection, to which 100% of the products are subjected. These techniques have been introduced in the production of carbide rolls by the method of controlled hot vacuum pressing. They have become an integral part of the quality control system for carbide rolls.

The 3-mm-thick plate joints of the UNS S32750 were successfully established using cold transfer welding (CMT) technology with Inox 2509 MoW B as filler. Metallography studies indicated that the austeno-ferrite phase equilibrium in the HAZ and weld seam was greatly affected compared to the base metal. The occurrence of various forms of austenite, i.e., grain boundary austenite, Widmanstatten austenite, and intergranular austenite, was observed in the CMT weld seam. While there was a slight increase in hardness, tensile failures occurred in CMT welds during tensile failure tests. The absence of secondary austenite and deleterious intermetallic phases in the CMT weld has improved the joint strength and moderate ductility. A ductile–brittle transition is observed in both the base metal and the CMT-welded joints when subjected to an impact load at sub-zero temperatures.

The paper details the studies carried out on a dual-size particulate composite prepared by stir casting using A 356 aluminum alloy and B4C powders. Three composite compositions, viz., A356 plus 2% B4C (44µm size and 105µm size in 1:1 ratio), 4% B4C (3:1 ratio), and 6% B4C (1:3 ratio) were cast in finger molds, from which test specimens were prepared for hardness and tensile tests as well as for metallography. Vickers hardness tests, tensile tests and microstructure analysis using an optical microscope were conducted. The results obtained indicated that the B4C particles were evenly distributed in the alloy matrix. EDS also revealed the presence of B4C in all the three composites. In general, the hardness and tensile strengths increased with increase in concentration B4C powders. While the increase in hardness was increases less than 15%, there was significant increase (more than 35 %) in tensile strength. However, the ductility represented by % elongation, which was already very low in A 356 cast alloy (24.2%,), further decreased in composites. Tensile fractography results shows inter crystalline fracture where the breakage in the B4C particle instead of deboning were observed.

The preparation of metallographic sections from soft metals such as pure copper constitutes a particular challenge: the high degree of ductility promotes the formation of preparation artifacts and complicates the preparation of homogeneous, low-deformation surfaces. A metallographic preparation routine is therefore presented which has proven effective for pure copper and which can also be applied to additionally soft annealed samples. The subsequent removal of fine crystalline deformation layers is discussed and different setups for electropolishing and its optimization are presented.

The structure and physical and mechanical properties of a 17GS steel specimen cut from a main gas pipeline section under use for over 50 years at a working pressure of 5.5 MPa is investigated in this study. The pipe under study laid in a straight-line segment and covered with sand was in service according to regular parameters. Metallography studies using methods of optical and scanning microscopy for analyzing transformations in the crystal structure of the metal are carried out. Mechanical tests are focused on the impact strength and static tension to determine changes in the physical and mechanical properties. The data obtained are compared with the as-delivered state specified by the manufacturer, currently accepted standards and industry requirements for pipes intended for reuse. The research reveals the basic mechanical characteristics of the steel to be virtually the same as those stated by the manufacturer; no structural transformations in the metal are found. The principal degradation process in the specimen of interest is identified to be sub-surface corrosion occurring no deeper than 100 µm. from the result of this study is that changes in the structure and mechanical properties appear insignificant over 50 years of service provided that the maximal stress in the pipes is below the limit of macroelasticity.

En este trabajo se analiza el efecto que tiene la temperatura de revenido en las propiedades microestructurales, cristalográficas y de desgaste del acero AISI/SAE 1045. Las muestras se obtuvieron por mecanizado de una varilla de 5/8´´ de acero comercial AISI/SAE 1045, hasta obtener probetas cilíndricas de 40 mm de diámetro y 5 mm de espesor. Estas muestras se sometieron a tratamientos térmicos de normalizado, temple y revenido, el cual se realizó a temperaturas de 460 °C, 507 °C, 554°C y 600 °C, esto con el fin de abarcar el rango de temperaturas de revenido recomendadas, por la literatura y los fabricantes de acero, para este material. En el ensayo de desgate adhesivo se utilizó un tribómetro pin-on-disk, para obtener tasa de desgaste de las muestras sometidas a las diferentes condiciones de revenido. Las huellas de desgaste se analizaron por medio de microscopia electrónica de barrido. La microestructura obtenida en cada tratamiento térmico se analizó mediante estudios de metalografía. Así mismo se realizaron medidas de dureza a las diferentes condiciones de revenido.

The alloys K90941 and N08811 were tested under conditions simulating a pyrolysis process of post-consumer plastics. Impurities in the plastic feedstock like chlorine containing materials or organic components yield HCl and H2S respectively during the cracking process. The reactor material must be able to withstand these harsh corrosive conditions.In lab-scale test equipment, process conditions of the reactor zone of the pyrolysis process were simulated at temperatures of 420 °C and 580 °C for 72 h. The gas atmosphere consisted of either 200 ppm or 20000 ppm H2S and 3.8 vol% HCl, 1.9 vol% CO2, 0.3 vol% CO, 2.8 vol% H2, bal. N2. After the corrosion experiments, the samples were analyzed by metallography, SEM/EDX, and XRD. Additionally, the mass loss was evaluated. Results show that the ferritic K90941 is more aggressively attacked than the austenitic N08811 and that for both materials the mass loss rises with increasing H2S content in the gas atmosphere and increasing temperature.

Fatigue crack growth (FCG) behavior of the bimodal (equiaxed and columnar) grain microstructure of Scalmalloy, which is a printable and high strength aluminum alloy, processed by laser powder bed fusion (LPBF) has been studied. Experimentally, FCG tests have been conducted using FCG samples with crack growth direction normal, parallel or 45° to build direction. Tested sample conditions include LPBF with room temperature base plate or heated base plate and as built state or heat-treated state. It has been found that the fatigue crack propagation threshold (ΔKth) values vary insignificantly and are 1.3-1.4 MPa m1/2 for all samples. Metallography examination of samples has shown that the crack path is highly smooth in the sub-micron grain-size equiaxed grain regions and is also generally smooth in the columnar grain regions with zigzag magnitudes no more than 2 μm. Fractography examination has also confirmed the lack of tortuosity in crack path. It is suggested that the small grain nature after LPBF provides little roughness-induced closure mechanism, resulting in low ΔKth values. In Paris region, m = 2.9-3.0 and C = (3-5) × 10-10MPa m1/2, in agreement with the values found in most aluminum alloys.

This study investigates the premature failure of an axial flow valve used in a gas flow control station. After the first reports of these valves' malfunction exposed to severe gas/solid flow, they were disassembled. It was found that their common issue was the erosion of radial slits of the valve cage closures (VCCs) made of 17-4 PH stainless steel. Metallurgical failure analysis on the eroded slits was performed through spark emission spectroscopy, metallography observations, hardness measurements, and scanning electron microscopy equipped with energy-dispersive spectroscopy. The results presented show that the major microstructure of the slits was martensitic with an average hardness value of 387 HV; however, unlike the common 17-4 PH alloys, the Al content of the VCCs was around 0.25 wt.% which is about 8 times higher than the common ones. The comparison of microstructure, hardness, impact toughness, and erosion rate of the failed VCCs with the standard reference composition 17-4 PH samples revealed that this level of Al content changes the phase balance of 17-4 PH and increases the amount of δ-ferrite from 1.1% to 4.7%. In addition, Al-rich inclusions with sizes less than 5 μm form throughout the microstructure of failed VCCs. These microstructural changes lead to around 50% decrease in the impact toughness and erosion resistance. A meaningful increase in the amounts of Al-rich inclusions and δ-ferrite/martensite interface are discussed as the potential mechanisms of severe erosion of VCCs and consequently malfunction of the axial gas flow valves.

The high-speed welding of friction stir welding can improve the production efficiency of the equipment. The orthogonal experiment method was used to study the high-speed welding process parameters of aluminum alloy. The mechanical properties of welded joints were tested, and the influence of process parameters on welding quality was analyzed. A data collection platform was designed, and the spindle axial force of the spindle and the three-directional force of the worktable were collected during the welding process. The relationship between the process force and process parameters was studied. From the perspective of macroscopic metallography, the causes of welding defects and the influence of process parameters are studied. The research results show that the mechanical properties of the welded joint are optimal and meet the requirements of welding quality when the process parameters are the tool rotational speed of 5000 rpm, the welding speed of 3000 mm/min, and the plunge depth of 0.25 mm.

The high-rate convergence of copper cylindrical shells with a diameter of 48 mm and a wall thickness of 4 mm is studied at various intensities of explosive loading. Two structural mechanisms of the loss of stability of the radial deformation front are described. A diagram of structural changes reflecting the successive stages of the convergence process is presented. An interrelation is found between the number of protrusions on the shell surfaces during their corrugation at the intensity of explosive loading. It was found that high-rate longitudinal deformation during convergence has a pulsating character. It was found that the temperature rises to ~500°С in the center of the converged shell and that it can be higher than 1000°С at a high rate of spall-pore collapse.

Failure of tubes is a very critical problem in boilers. The current study describes the detailed investigation for failure of boiler tubes in the power plants. Different characterization techniques like; metallography/microscopy, hardness, chemical analysis, SEM/EDS were utilized to find out the actual cause of failure. The tubes were failed within one year of its service. It was concluded that the brittle fracture (rupture) of tubes was occurred due to over-heating caused the formation of thermally insulating thick iron oxide scale on the inner surface of the boiler tube. Evidence of hydrogen embrittlement of the boiler tube in the rupture region was also found. Insights of this investigation might be helpful for the prevention of this type of failures in future.

The fatigue crack propagation (FCP) behavior of FSW welded 7050-T7451 joints was studied using compact tensile specimens. Based on Paris law and three-stage theory of FCP, the FCP rate of joint was obtained by data fitting and calculation. The fracture morphologies at different stages of FCP were characterized by metallography and scanning electron microscopy (SEM). Results showed that the FCP rate in each region for FSW joint was as follows: heat affected zone (HAZ) > weld nugget zone (WNZ) > base metal (BM). In the first stage of FCP, the fracture morphologies of BM and HAZ were mainly tearing ridges and river pattern. There were a small number of dimples on the fracture of BM, but no dimples on the fracture of HAZ. In the second stage of FCP, the fatigue striations of the BM were denser and finer than those in the HAZ, and have dimple fracture characteristics. In the third stage of FCP, dimples still existed in the fracture surface of the BM, and the fatigue striations disappeared. The HAZ was dominated by lamellar tearing and cleavage fracture without dimples. During the three stages of FCP, the fracture morphology of the WNZ in the first and second stages was fine dimple fracture with significant equiaxed deep dimple morphology. In the third stage, the fracture dimple in the WNZ changed from equiaxed deep dimples to tearing dimples.

The laser process parameters used in selective laser melting (SLM) affect the mode of melting and the process characteristics such as the porosity. Some parameters may have a higher effect on the single-track characteristics than the others. This study aims at determining both the individual and combined effects of laser parameters on the single-track geometry and porosity for Inconel 625 alloy powder. The single tracks with linear energy densities (LED) ranging from 0.16 to 0.98 J/mm are fabricated to explore the effect of LED on melting modes and the keyhole porosity. A micro-CT scanner is used to measure the pores formed inside the tracks, and the results showed that the porosity increased with an increase in LED in the keyhole mode. Besides, metallography is performed to reveal the transverse melt pool boundary and to differentiate the melting modes. The transverse melt pool boundary shows that the depth of the melt pool increases significantly compared to the width with an increase in LED, which signifies the change in the melting from the conduction to keyhole mode. Further, another set of experiments is performed by using different combinations of laser power and scan speed from the same LEDs of 0.48 J/mm and 0.75 J/mm. The melt pool boundary shows that within the same LED, the depth of the melt pool increases significantly with an increase in the laser power. However, for the same LED, the single-track porosity increased up to a certain level; then, the porosity decreased with the further increase in the power and speed. The physics behind such phenomenon is explained by the particle-level SLM process simulations developed using FLOW-3D. The simulation results show that the change in the melting mode from the conduction to keyhole for the same LED is due to the increased vaporization with an increase in the laser power, which enhanced the vapor pressure.

Shape memory alloys (SMAs) are increasingly used in a wide range of thermomechanical and thermoelectric applications that are of a macro-, micro- and nano-scale. Though the use of commercial Ni–Ti (NiTiNOL) SMAs is preferred in most of these applications, there is an ever-increasing demand for cost-effective and easy-to-produce alternatives to NiTiNOL. In terms of functional properties, copper-based SMAs are comparable to Ni–Ti SMAs. Moreover, Cu-based SMAs are cheaper and easier to produce and process. In order to improve the functional properties of binary Cu-based SMAs (Cu–Al, Cu–Zn and Cu–Sn), ternary elements are added in small quantities. This is also one of the most common methods that is used to improve the functional properties of NiTi- and Fe-based SMAs. In this work, Cu–Al-based alloys containing ternary elements, Mn, Sn, Te and Hf, were produced by arc melting technique. Thermal (DSC, DTA) and microstructural (XRD, metallography) analyses were then carried out on the alloys prepared so as to characterize them for their thermal and microstructural characteristics. The results demonstrate improved shape memory properties for these alloys. The transformation temperatures of the binary Cu–Al alloys determined showed higher values (Af > 100 °C). Among the ternary alloys, the highest transformation temperatures were found for alloys with Hf addition, followed by those with Te addition. But on the other hand, the most intense peaks corresponding to the martensitic transformation were observed for Sn addition. The microstructural investigations revealed the presence of martensite in the alloys which was consistent with the results of thermal analysis.

The corrosion behaviour of as-rapidly solidified and heat treated AI 8Ni-2Co alloy ribbons produced using melt spinning technique was investigated. The decomposition behaviour of the rapidly solidified ribbons was followed up using x-ray diffraction, differentialscanningcalometry. microhardness, and metallography. The stable phases which are generally formed in conventional solidified alloy in the as cast condition, were not detected in the as-rapidly solidified specimens. Instead, super-saturated solid solution α-AI was present in addition to fine dispersoids of A19(CoNi)2. The corrosion behaviour was investigated through potentiostatic technique in 3.5% NaCL aqueons solution. The corrosion rate was the lowest in the as-rapidly solidified condition and increased with increasing the annealing temperature as a result of the formation and coarsening of the intermetallic Al3Ni.

Grain coarsening prevention while accelerating the carburizing process is critical for the manufacturer for case hardening components such as gears to improve efficiency. In this research, a novel method is proposed to prevent austenite grain growth by introducing the ferrite phase that could retard the austenite boundary movement. The addition of aluminum promotes the ferrite phase. Aluminum as strong ferrite former raises the A3 temperature so that the ferrite phase is present at high carburizing temperature. The effect of 1 wt.% aluminum on the microstructure evolution during pseudo-carburizing treatment in 20CrMn steel is investigated in details. It is shown that the formation of ferrite during pseudo-carburizing at 930 °C for 5h prevents austenite grain coarsening. The obtained mechanical properties are similar to non-aluminum added 20CrMn steel pseudo-carburized at 830 °C for 16h. When 20CrMn was pseudo-carburized at 930 °C for 5h, significant austenite grain growth was observed, which result in low impact toughness after the subsequent quenching and tempering treatment. The “ferrite pinning” effect effectively inhibits the grain growth at high temperature, revealed by metallography investigation.

The solidification mechanism and segregation behavior of laser-melted Mn35Fe5Co20Ni20Cu20 was firstly investigated via in-situ synchrotron x-ray diffraction at millisecond temporal resolution. The transient composition evolution of the random solid solution during sequential solidification of dendritic and interdendritic regions complicates the analysis of synchrotron diffraction data via any single conventional tool, such as Rietveld refinement. Therefore, a novel approach combining a hard-sphere approximation model, thermodynamic simulation, thermal expansion measurement and microstructural characterization was developed to assist in a fundamental understanding of the evolution of local composition, lattice parameter, and dendrite volume fraction corresponding to the diffraction data. This methodology yields self-consistent results across different methods. Via this approach, four distinct stages were identified, including: (I) FCC dendrite solidification, (II) solidification of FCC interdendritic region, (III) solid-state interdiffusion and (IV) final cooling with marginal diffusion. It was found out that in Stage I, Cu and Mn were rejected into liquid as Mn35Fe5Co20Ni20Cu20 solidified dendritically. During Stage II, the lattice parameter disparity between dendrite and interdendritic region escalated as Cu and Mn continued segregating into the interdendritic region. After complete solidification, during Stage III, the lattice parameter disparity gradually decreases, demonstrating a degree of composition homogenization. The volume fraction of dendrites slightly grew from 58.3–65.5%, based on the evolving composition profile across a dendrite/interdendritic interface in diffusion calculations. Postmortem metallography further confirmed that dendrites have a volume fraction of 64.7% ± 5.3% in the final microstructure.

Nowadays, there are several important reasons for using high-strength sheets in the manufacture of car bodies. Car manufacturers choose the steel with good formability, fatigue resistance and ability to absorb impact energy. One of these materials, which fulfil above mentioned criteria are microalloyed steels and dual-phase steels. The application of high-strength sheets has led to develop new materials joining techniques. Mechanical joining such as clinching is the innovative technique to join these progressive materials. Materials of different thicknesses can be joined by clinching. The paper focuses on the comparison of the properties of the joints made by clinching and resistance spot welding. The application of resistance spot welding is still the most used joining method in car body production. These properties were investigated by tensile test and metallographic observation. Steel sheets HCT600X+ZF, HCT600X+Z and HX420LAD+Z were used for the experiments. The results of tensile test show that the values of load-bearing capacity of clinched joints reached from 3900 N to 5900 N and resistance spot welded joints reached the values of load-bearing capacity from 12000 N to 19500 N. In comparison to the resistance spot welded joints, the clinched joints reached from 32 to 48% of load-bearing capacity.

The work was aimed at analysing the effect of boron on austenite grain size of low-alloy cast steels during austenitization in the range between 850°C and 1200°C. The effect of boron was investigat...

Industrial-scale extruded profiles of AA 7108 with a rectangular section (25.60 mm x 15.95 mm) were used in this investigation. Some complementary microstructural analysis techniques, such as polarized light microscopy, EBSD (Electron Backscatter Diffraction) and X-ray diffraction were used to characterize the microstructure, focusing on the PCG zone. It was observed that the extruded profiles presented a totally recrystallized microstructure and a 300 μm layer of peripheral coarse grains. Additionally, the results showed that the PCGZ predominant grain orientation {311} differs from the texture below the PCGZ (Goss and Cube components).

This work examines the grain refinement and mechanical properties of additive friction stir layer welding (AFSLW) of a Mg Alloy. The AFSLW process was used to additively fabricate a seven-layer tall build using 5-mm-thick plates of AZ31 Mg alloy, with each layer containing three parallel welding passes. This multipass AFSLW process demonstrates the ability of this additive method to produce tall and wide structures free of volumetric defects. While the AFSLW material was found to have lower monotonic tensile and fatigue strengths as compared to wrought Mg AZ31-H24, this result was expected due to the heat input from the additive layer welding process that relaxed the cold work strengthening mechanisms. Metallography cross sections and analysis via scanning electron microscopy revealed that the AFSLW build did not contain any detectable defects in any of the 21 weld passes. Furthermore, postmortem fractography found fatigue crack initiation mechanisms to be similar in both the AFSLW and wrought AZ31-H24. The results of this study indicate that large, defect-free builds with predictable mechanical properties can be achieved using the AFSLW process.

The structure of nickel-free duplex steel based on the Cr-Mn-Mo system with a high nitrogen content (0.34% N), formed as a result of heat treatment in accordance with various quenching and aging schemes, is investigated. Used methods of metallography, x-ray phase analysis and hardness measurements. During heat treatment, austenite and ferrite of the studied steel underwent decomposition with the formation of nitride and intermetallic phases, and also underwent polymorphic transformations. Separation of ferrite was also observed with the formation of a chromium-enriched phase (αCr). The duplex structure of the studied steel (with a content of each phase of about 47%) was obtained after quenching from 1150° C and thermal exposure at a temperature of about 700° C for one hour.

Studies are made to utilize the industrial solid waste of ferrochrome (Fe-Cr) slag as reinforcement to make particulate Polymer matrix composites (PMCs). Fe-Cr slag exhibits hard and high strength also consist multiple oxides of SiO₂, Al₂O3, MgO, Fe₂O3 and Cr2O3. Three different sizes (500 µm, 210 µm and 45 µm) were chosen as reinforcement in E glass fiber and epoxy resin matrix. Hand lay-up technique adopted to process all the PMCs. Metallography and mechanical properties evaluation has been done on all these PMCs. SEM studies reveals the homogeneity in the particles distribution and good interfacial bonding between matrix and reinforcements. Improved mechanical properties were observed for all the slag particulates PMCs. However, size of the slag particles also contributing the performance of the composites. Neither coarse (500 μm) nor very fine (45 μm) particles but optimum size of 210 μm slag particles is stimulating to increase the strength of the proposed composites.

Friction stir welding (FSW) employs a tool that does not require any filler materials; frictional heat is produced and performs a solid-state joining method. Severe plastic deformation causes to join similar and dissimilar materials without melting the workpiece at the welding line. Friction stir welding is the most recent friction welded joining processes with the most surprising features when welding various metal alloys, including magnesium, aluminium, copper, and steel. FSW is victorious of all the other conventional welding methods implied in many industrial applications like automobile, aerospace, fabrication, shipping, marines and robotics. It gives high-quality welds, energy input, and distortion are lower, better retention of mechanical properties; it is eco-friendly and can be performed less operating cost. This research work aims at the FSW process in Al-Cu alloys, highlighting:(a) Optimizing the welding process parameters, welding feed rate, tool rotation speed, (b) Evaluation of Electrical Conductance properties of joints, (c) Mechanical properties and metallography characteristics of joints.

Laser welding of copper to aluminum is challenging due to the formation of complex intermetallic phases. More Al (~18.5 at. %) can be dissolved in Cu, in contrast to Cu (~2.5 at. %) in Al. Therefore, welding from copper side, large melting of Al can be achieved. However optimum Cu and Al must be melted for a strong joint. Finding the right amount is difficult and time consuming by tradition analysis technique like inspection by weld cross-sections. Considering the speed of the welding process and complexity of analysis involving with metallography cross-sections, alternative rapid method to qualify the welds are necessary. The acoustic emission during laser welding can give proportional information of the Al, Cu melted. With such an approach the weld status can be obtained in real time. In this paper the acoustic welding signal using an airborne sensor in the audible range of 20 Hz to 20 kHz, is correlated to the weld strength and material mixing (Al, Cu melt). Finally, the weld status is predicted by an artificial neural network based on the acquired signal.

Additive manufacturing processes allow the production of geometrically complex lightweight structures with specific material properties. However, by contrast with ingot metallurgy methods, the manufacture of components using this process also brings about some challenges. In the field of microstructural characterization, where mostly very fine structures are analyzed, it is thus indispensable to optimize the classic sample preparation process and to furthermore implement additional preparation steps. This work focuses on the metallography of additively manufactured Ti‑6Al‑4V components produced in a selective laser melting process. It offers a guideline for the metallographic preparation along the process chain of additive manufacturing from the metal powder characterization to the macro- and microstructural analysis of the laser melted sample. Apart from developing preparation parameters, selected etching methods were examined with regard to their practicality.