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In this work, three different states of Mg-9.1Y-1.8Zn alloys including as-cast, extruded and swaged were prepared by semi-continuous casting, extrusion and swaging processes, respectively. Their compositions, microstructures and hydrogen storage properties were investigated. The results show that Mg-9.1Y-1.8Zn alloys in three different states are all composed of Mg and long-period stacking ordered (LPSO) phases. The LPSO phases occurs to break and decompose after hydrogenation and in-situ forms the YH χ(χ = 2,3) nano-hydrides. The nano-hydrides can be used as in-situ catalysts to improve the hydrogen storage properties of alloys. Meanwhile, many nanocrystalline grains appear in the core of alloy after swaging, and the average grain size ranges from 80 to 200 nm. The presence of nanocrystals may increase the specific surface area of alloy, facilitating the diffusion and absorption of hydrogen. Comparatively, the swaged alloy exhibits the largest hydrogen storage capacity and excellent hydrogen sorption kinetics relative to other states of alloys. • The as-cast, extruded, and swaged Mg-9.1Y-1.8Zn alloys were prepared. • The LPSO phases decomposes and in-situ forms YH χ(χ = 2,3) hydrides upon hydrogenation. • The YH χ(χ = 2,3) hydrides present in-situ catalytic and pinning effects on Mg matrix. • The swaged alloy exhibits the highest hydrogen storage capacity. [ABSTRACT FROM AUTHOR]

Abstract The research aims to analyze the impact that severe plastic deformation arising during Rotary Swaging has on mechanical properties and corrosion resistance of a near-α-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M). The nature of corrosion decay in fine-grained alloys caused by hot salt corrosion is known to vary from pit corrosion to intercrystalline corrosion at the onset of recrystallization processes. Resistance to hot salt corrosion in a fine-grained titanium alloy Ti-2.5Al-2.6Zr is shown to depend on the structural-phase state of grain boundaries that varies during their migration as a result of "covering" corrosive doping elements (aluminum, zirconium) distributed in the crystal lattice of a titanium alloy. Highlights • Fine-grained (FG) structure in near-α-alloy Ti-2.5Al-2.6Zr was formed with Rotary Swaging. • Hot salt corrosion mechanisms in coarse-grained (CG) and FG alloys are studied. • Corrosion defects of type I in a CG alloy are stitched as a result of β-phase particles precipitation. • Corrosion defects of type II in a CG alloy look similar to intercrystalline corrosion (ICC). • Corrosion decay in a FG alloy changes from pit corrosion to ICC when the migration of grain boundaries starts. [ABSTRACT FROM AUTHOR]

Abstract A high performance Cu-Cr-Zr alloy with an ultimate tensile strength of 612 MPa, a uniform elongation of 5% and an electrical conductivity of 84.7% IACS was achieved by the severe rotary swaging and two-step peak-aging treatment. A perfect ultrafine grained microstructure with uniformly distributed nano-precipitates was identified to be responsible for the excellent properties of the studied alloy. The proposed method of rotary swaging in combination with the two-step aging treatment shows good potential for producing the high performance Cu-Cr-Zr alloy, which can not only fulfill the industrial requirement of strength and electrical conductivity, but also is suitable for mass production. [ABSTRACT FROM AUTHOR]

Nano-sized ZrC dispersion strengthened tungsten alloy (W-0.5wt%ZrC) rods with enhanced mechanical properties and superior high-temperature stability were fabricated by high temperature rotary swaging. The effects of swaging and annealing on the microstructure and mechanical properties of W-0.5wt%ZrC alloys were investigated. The as-swaged W-0.5%ZrC rod showed noticeable ductility at 200 °C with a total elongation of 4.2% and a tensile strength of 724 MPa, and at 500 °C the strength remains as high as 547 MPa and the total elongation is 28%. The ductile-to-brittle transition temperature (DBTT) is about 200 °C. The recrystallization start temperature of swaged W-0.5wt%ZrC is about 1500 °C, which is about 300 °C higher than that of rolled pure W. The possible mechanisms for the enhanced mechanical properties and thermal stability were discussed. [ABSTRACT FROM AUTHOR]

Highlights • Current status of Charpy impact properties of pure and modified W materials are reviewed. • Impact properties of W are dependent on fabrication methods and histories regardless of their major chemical composition. • DBTT and USE of pure W from different production routes could be integratedly understood using Hall-Petch type relations. Abstract One of the most critical issues affecting tungsten (W) as plasma facing material is ductile-to-brittle transition behavior. It is well known that the microstructure of W materials is influenced by the fabrication methods and histories, which can affect those behaviors. In this paper. the current status of Charpy impact properties (ductile-to-brittle transition temperature (DBTT) etc.) of pure and modified W materials fabricated by several methods and histories are reviewed based on the open literatures and the possibility of integrated interpretation of Charpy impact properties of W materials from different production routes is discussed. [ABSTRACT FROM AUTHOR]

Five different compositions of tungsten heavy alloy with Ni, Fe, Co and Mo were prepared through powder metallurgy route using liquid phase sintering. Three alloys were based on quaternary W-Ni-Fe-Co (with varying Ni to Fe ratio and Co content) and the other two quinary systems with Mo addition. The sintered alloy blanks (cylindrical cross section) were subjected to a thermo-mechanical treatment, which comprised three vacuum heat treatments (at 1100 °C for 1.5 h followed by oil quenching) before and in between multiple swaging operations (at 500 °C) with a total deformation of 53%. This was followed by a detailed evaluation of different microstructural parameters in all compositions. Mechanical properties such as tensile strength, % elongation and impact were evaluated at the final stage (26 mm dia and 600 mm length). Increase in Co content resulted in better strength and elongation with marginal loss in impact values. The alloy containing 0.25 wt% Mo showed the best combination of tensile and impact properties. Further increase in Mo concentration to 0.5 wt% resulted in marginal increase in strength value but rapid deterioration in elongation and impact values. Scanning electron microscopy, electron probe micro analysis, quantitative metallography and fractography were carried out to establish an inter-relationship between microstructure, properties and fracture behaviour of the alloys investigated. [ABSTRACT FROM AUTHOR]

TiC reinforced titanium matrix composites are promising for advanced applications. Generally, the relative density of the composites and the interfacial bonding between the matrix and reinforced particles may have a great influence on the mechanical properties. This study presented the fabrication of the full-densified Ti-15Mo-xTiC (x = 1.5, 3.0, 4.5 wt%) composites through in-situ reactive sintering of Ti, Mo, and MoC powders and hot swaging process. Experimental results show the formation of TiC and the absence of MoC in the fabricated composites. After hot swaging, the TiC particles showed aligned distribution along the swaging direction, and exhibited well bonding with the β-Ti matrix. Increasing the TiC content leads to increase tensile strength and Young's modulus but decrease elongation. Ti-15Mo-4.5TiC offers and outstanding combination: ultimate tensile strength = 1290 MPa, yield strength = 1075 MPa, Young's modulus = 89 GPa, and tensile elongation = 3.1%. The strengthening effect is attributed to Mo solid solution in Ti matrix, β-Ti grain refinement, and TiC particle reinforcement. The specific contribution of each mechanism is quantitatively calculated, showing good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

9Cr2WVTa ferritic/martensitic steel was processed by cold-swaging and post-annealing in order to investigate the microstructure evolution and its effect on the mechanical properties. Optical microscopy, scanning electron microscopy with electron backscatter diffraction, and transmission electron microscopy were utilized for the microstructural characterization during the cold-swaging and post-annealing process, and the mechanical properties were determined by microhardness, tensile and creep tests. The results revealed that, nearly equiaxed ultrafine grains with the average size of ~ 330 nm and fine dispersed carbides with the average length of ~ 50 nm, were obtained after cold-swaging and post-annealing. In comparison with the initial normalized-tempered sample, effective grain boundary strengthening and dispersion strengthening in the post-annealed sample enhanced the strength at room and elevated temperature. The presence of fine dispersed carbides could retard the initiation and propagation of the cracks, leading to a better ductility in the post-annealed sample. During creep test, fine dispersed carbides in the post-annealed sample effectively slowed down grain boundary migration. The pinned grain boundaries and fine dispersed carbides in the post-annealed sample acted as obstacles to the motion of mobile dislocations, which resulted in the enhanced creep properties. [ABSTRACT FROM AUTHOR]

Evolutions of texture and lattice strain of swaged brass samples were investigated by neutron diffraction at STRESS-SPEC under tensile deformation using a unique tension/compression rig. The two phased sample BS1 (61% α-brass and 39% β-brass) became 100% α-brass after 400 °C annealing (sample BS2). The starting texture of the as-received material BS1 was the typical <111>, <200> double fiber. This texture develops firstly by in-situ tension to a moderate strengthening. After annealing (BS2) the <111> fiber survives with surprisingly high strength and develops by in-situ tension a very strong <111> fiber of 39 mrd. Line broadening and lattice strain behaviour shows the development of the elastic strain and plastic strain. [ABSTRACT FROM AUTHOR]

A rotary swaging process is presented which allows the manufacturing of smart structures by forming hollow shafts and joining sensor elements simultaneously. A reasonable form- and force-fit of the sensor element is required to ensure the desired sensory properties of the structure, such as linearity, long-term stability and repeatability. However, the conjoint forming process is subjected to uncertainty which leads to fluctuations of the sensor loads and the remaining pre-tension forces. In order to increase the adjustability and accuracy of the process, the utilization of the sensor signals for a control approach is investigated. The infeed and the mandrel force are found to be potential control parameters and the possible time slot of an intervention is identified. A first control approach is implemented and shows an improvement in accuracy of around 65% compared to the uncontrolled process. [ABSTRACT FROM AUTHOR]

In this work, two post sintering hot deformation processes were applied on Alumix 321 PM alloy which is a commercially available aluminum powder alloy which can be considered equivalent to the wrought AA6061 alloy. The powder was compacted, sintered, and then either hot swaged or hot rolled. The results show that both hardness and density were improved as a result of the applied post sintering treatment. Theoretical density (TD) of 99.1% and 99.39% were recorded for the hot rolled and hot swaged alloys, respectively. T6 hardness improves to 106 ± 6 HRE and 96 ± 2 HRE for hot rolled and hot swaged alloys, respectively. The performance was assessed in terms of corrosion behaviour by testing the Alumix 321 PM alloy in as sintered, and as hot deformed conditions after exposure to 3.5 wt% NaCl solution. Electrochemical techniques were used to study the effect of hot deformation on corrosion behaviour. Corrosion current density decreases as a result of hot swaging and hot rolling and in both cases the values were less than those of the wrought counterpart, AA6061 alloy. The stair step polarization was applied; the results obtained support that the technique seems promising to bridge the gap between traditional and accelerated corrosion test methods. Pitting was the main corrosion mechanism for the wrought alloy while, pitting, crevice, and intergranular corrosion were observed for the PM alloys. [ABSTRACT FROM AUTHOR]

HfC dispersion strengthened tungsten alloys were prepared by the spark plasma sintering (SPS) and an ordinary sintering followed by swaging, respectively. The HfC content is optimized as 0.5 wt% through spark plasma sintering (SPS) processing. The thermal stability, thermal conductivity and mechanical properties of swaged W-0.5 wt%HfC (WHC05) alloys were systematically investigated. Grain of swaged WHC05 has an obvious round bar shaped morphology with an average diameter of 24.5 μm and an average length of 187 μm, respectively, which keeps stability with increasing annealing temperature up to 1400 °C. The ductile-brittle transition temperature of swaged WHC05 is about 250 °C, much lower than that of SPSed WHC05 samples (∼500 °C). The ultimate tensile strength of swaged WHC05 alloys annealed at 1200 °C has no significant drops in a wide tested temperature range from 300 °C to 800 °C. The thermal conductivity of swaged WHC05 annealed at 1200 °C is up to 174 W/m·K at room temperature and always larger than 137 W/m·K from RT to 500 °C, which is much higher than that of the unannealed one and just the same with ITER grade W. [ABSTRACT FROM AUTHOR]

Influence of mechanically alloyed tungsten-rhenium powders on the microstructure and mechanical properties of liquid phase sintered 89W-7Ni-3Fe-1Re heavy alloy was studied. Heat treatment and swaging were conducted on alloys prepared using both conventionally blended and mechanically milled powders. The results indicated the formation of bcc solid solution by high energy milling of tungsten and rhenium powders. The corresponding particle and the crystallite size decreased after high energy milling. Grain size and contiguity of the milled alloy were significantly lower than those of conventional counterpart. The alloy prepared using high energy milled W-Re powder exhibited relatively superior balance of strength, ductility and impact toughness. These findings suggest that refractory powder mechanical alloying prior to sintering is beneficial for improving the mechanical properties of tungsten heavy alloys. [ABSTRACT FROM AUTHOR]

Fe 50 Co 50 was subjected to incremental forming by rotary swaging with the aim of tailoring the coercivity by changing the microstructure. The challenging part of a deformation of Fe 50 Co 50 is an ordering phase present at room temperature, leading to low formability. To increase the formability of the alloy the presence of the ordering phase was supressed by two different concepts. The first concept consists of a heat treatment above the phase transition followed by rapid cooling and deformation at room temperature. The second concept was rotary swaging at temperatures above the phase transition temperature. A comparison in terms of resulting microstructure and magnetic properties shows that both concepts have a potential for tailoring the coercivity of Fe 50 Co 50 . [ABSTRACT FROM AUTHOR]

Umbilical cables are important components in underwater oil extraction, providing electro-hydraulic connection between platform and manifold in oil well, through elements such as electrical cables and thermoplastic hoses. The connections of thermoplastic hoses are made with fittings installed by a cold forming process, called swaging, to ensure a perfect seal. These fittings are made of SAE AISI 316L stainless steel, but in order to reduce manufacturing costs, SAE AISI 1045 carbon steel fittings are used in hose factory acceptance tests. However, longitudinal cracks were produced during swaging of carbon steel of a specific supplier. In this work, samples from two different suppliers were characterized before and after installation to understand the failure cause. The characterization was made by visual inspection, dimensional control, hardness tests, chemical composition, microstructural and fracture surface analyses. In addition, swaging process simulations by finite element method (FEM) using a commercial software were performed. The results indicated large variations in material elements percentage from the supplier with failed connections history. This fact resulted in elevated amounts of non-metallic inclusions which promoted the cracks. Finally, corrective actions were recommended to mitigate the failure occurrence. [ABSTRACT FROM AUTHOR]

A process sequence enabling an efficient production of hollow sensory machine elements with adapted wall-thickness and a smooth outer contour is presented. The applied conjoint forming approach aims to simultaneously form a tubular part to its final shape whilst integrating a functional element into it. Additionally, the forming process is adjusted in order to set up a pre-tension in the assembly. Thus, a lift-off of the sensor element in case of tensile forces during application is prohibited and a high sensor linearity is ensured. In order to predict the achievable pre-tension and to determine the maximum process force, a three-dimensional numerical model is introduced. The underlying mechanisms of the pre-tensioning process are discussed on the basis of a forming process with and without a mandrel. A direct comparison of the two basic swaging strategies – recess and infeed swaging – reveals advantages of the infeed swaging strategy to achieve a high pre-tension of the assembly. The cold work hardening of the preform, the thermal heating and the machine stiffness are relevant phenomena of the process which influence the forces significantly. A detailed validation proves the necessity to include the mentioned effects in the numerical model. Furthermore, a trial of a sensory rod is presented. The high linearity of the sensory structure underlines the high potential of the proposed process to integrate sensor elements into massive metallic structures. [ABSTRACT FROM AUTHOR]

There is an increasing demand for precipitation-hardened Cu-Ni-Si alloys in the industry, where the high strength and moderate electrical conductivity are required. The main objective of this study was to apply a combination of microstructure refinement using swaging (SW) to generate an ultrafine-grained (UFG) microstructure in Cu-2.5 wt%Ni-0.5 wt%Si-0.06 wt%Mg (Cu-2.5Ni-0.5Si-0.06Mg), along with an optimized precipitation hardening. As a result, a substantial improvement of mechanical properties of the swaged samples (UFG condition) after precipitation hardening is apparent as compared to the precipitation-hardened non-swaged samples (coarse-grained (CG) condition). The mechanical properties of the UFG state are significantly superior to those of the CG state, i.e., a sharp increase in the elongation to fracture of 14% and a tensile strength of 800–900 MPa can be achieved. This study summarizes a detailed description of the microstructure after different processing steps using optical microscope (OM), electron channeling contrast imaging (ECCI) methods, and transmission electron microscopy (TEM), and presents the consequences on the most important mechanical properties such as the strength and ductility. [ABSTRACT FROM AUTHOR]

Roller swaging is an assembly process of self-lubricating spherical plain bearings, which provides a lightweight reliable joint by means of the plastic deformation with a small forming load requirement. The precise process control of the roller swaging is of great significance to ensure the assembly reliability and a good performance of the self-lubricating spherical plain bearing. In present investigation, the forming load analytical equations for various process parameters was proposed by a plane strain analysis considering the existence of a rigid end, which is a key mechanical factor that causes the metal flow in the roller swaging process. The effects of the feed distance, roller angle, feed speed and friction coefficient on the forming load are assessed in detail. What’s more, the metal flow in the roller swaging was revealed by a 3D elastic-plastic finite element model. The forming load was also obtained from the finite element model during the roller swaging process. Finally, the roller swaging assembly experiments were conducted with a roller swaging apparatus in laboratory conditions, and the good agreements are highlighted among theoretical calculation, FE simulation and experiment measured. [ABSTRACT FROM AUTHOR]

A finite element analysis was performed to predict behaviour of sintered tungsten-based heavy alloy during cold rotary swaging, while experimental investigations evaluated mechanical and structure properties in both, sintered and swaged material states. The simulation involved prediction of swaging force, which was subsequently compared with force measured experimentally using own designed force detection system, although other parameters, such as strain, strain rate, stress and temperature were also predicted and subsequently compared to experimental data. The results showed significant hardening and strengthening after swaging; the average ultimate strengths after sintering and swaging, respectively, were 860 MPa and 1680 MPa. This also contributed to very high swaging force of almost 600 kN. The distribution of microhardness across the cross-section confirmed the predicted strain distribution. Texture analyses revealed a notion of cube texture given primarily by the fcc matrix in the sintered state, while several ideal orientations for both the fcc and bcc phases were observed after swaging. As indicated by grains misorientations analyses, swaging introduced residual stress, the distribution of which was in conformity with the predicted stress and strain distributions. [ABSTRACT FROM AUTHOR]

This paper presents a new sheet-bulk forming process to locally pile-up material in thin sheets for subsequent forming or joining operations. An analytical solution is proposed for explaining the influence of the major process parameters, estimating the thickening of the pile-up material and determining the normal and thrust forces applied by the tools. The approach is built upon the slip-line field theory under plane strain assumptions and results are compared against finite element predictions and experimental results using Aluminium EN AW-1050A (EN 573-3) sheets with 3 mm thickness. The last part of the paper introduces a modified tool geometry that is able to control the pile-up material for subsequent mechanical fastening operations. [ABSTRACT FROM AUTHOR]

In this study, we investigated the evolution of the microstructure and mechanical properties during annealing of a cold-swaged Ni-free Co–Cr–Mo alloy for biomedical applications. A Co–28Cr–6Mo–0.14N–0.05C (mass%) alloy rod was processed by cold swaging, with a reduction in area of 27.7%, and then annealed at 1173–1423 K for various periods up to 6 h. The duplex microstructure of the cold-swaged rod consisted of a face-centered cubic γ-matrix and hexagonal closed-packed ε-martensite developed during cold swaging. This structure transformed nearly completely to the γ-phase after annealing and many annealing twin boundaries were observed as a result of the heat treatment. A small amount of the ε-phase was identified in specimens annealed at 1173 K. Growth of the γ-grains occurred with increasing annealing time at temperatures ≥1273 K. Interestingly, the grain sizes remained almost unchanged at 1173 K and a very fine grain size of approximately 8 μm was obtained. The precipitation that occurred during annealing was attributed to the limited grain coarsening during heat treatment. Consequently, the specimens treated at this temperature showed the highest tensile strength and lowest ductility among the specimens prepared. An elongation-to-failure value larger than 30% is sufficient for the proposed applications. The other specimens treated at higher temperatures possessed similar tensile properties and did not show any significant variations with different annealing times. Optimization of the present rod manufacturing process, including cold swaging and interval annealing heat treatment, is discussed. [ABSTRACT FROM AUTHOR]

The strengthening of biomedical metallic materials is crucial to increasing component durability in biomedical applications. In this study, we employ cold swaging as a strengthening method for Ni-free Co–Cr–Mo alloy rods and examine its effect on the resultant microstructures and mechanical properties. N is added to the alloy to improve the cold deformability, and a maximum reduction in area ( r ) of 42.6% is successfully obtained via cold swaging. The rod strength and ductility increase and decrease, respectively, with increasing cold-swaging reduction r . Further, the 0.2% proof stress at r =42.6% eventually reaches 1900 MPa, which is superior to that obtained for the other strengthening methods proposed to date. Such significant strengthening resulting from the cold-swaging process may be derived from extremely large work hardening due to a strain-induced γ (fcc)→ ε (hcp) martensitic transformation, with the resultant intersecting ε -martensite plates causing local strain accumulation at the interfaces. The lattice defects (dislocations/stacking faults) inside the ε phase also likely contribute to the overall strength. However, excessive application of strain during the cold-swaging process results in a severe loss in ductility. The feasibility of cold swaging for the manufacture of high-strength Co–Cr–Mo alloy rods is discussed. [ABSTRACT FROM AUTHOR]

A tungsten heavy alloy containing cobalt and molybdenum was subjected to thermo-mechanical processing that employed cyclic heat treatments in order to explore the possibility of enhancing mechanical properties. The alloy was synthesized by liquid phase sintering followed by heat treatments which consisted single as well as multiple cycles. Subsequently, these were subjected to warm swaging imparting about 30% deformation. Discernible changes were observed in the microstructure following cyclic heat treatment in both heat treatment and swaged conditions. While there was marginal increase in tensile properties, impact toughness showed significant enhancement. A detailed analysis of microstructure and fractographs was undertaken in order to understand the reasons for the enhancement in impact toughness and also the implication of these results in the development of heavy alloys with improved properties. [ABSTRACT FROM AUTHOR]

Deformation behaviors during swaging of an Al/Cu/Al layered clad composite were investigated experimentally and by finite element (FE) analysis. Measured and predicted deformation responses were compared and found to be in generally good agreement. These comparisons also validated the design and operation of a custom device that measures the total force required for swaging. An average effective strain of 0.5 was predicted for the first swaging pass, but the strain distribution was significantly inhomogeneous. Predicted strain gradients and stresses were consistent with experimentally observed gradients in grain size and subgrain size. The highest flow stresses were predicted in the Cu layer, where the measured subgrain size was correspondingly small. The predicted gradients in temperature and strain also correlated well with the observation of recrystallization in the outer Al layer. [ABSTRACT FROM AUTHOR]

The processing parameters which govern the evolution of microstructure and texture during rotary swaging and subsequent heat treatments were studied in an equiatomic single-phase CoCrFeMnNi high-entropy alloy. After vacuum induction melting and casting, the diameter of the 40 mm cast ingot was reduced at room temperature to a final diameter of 16.5 mm by rotary swaging (diameter reduction of 60%/area reduction of 80%) and the alloy was then annealed at different temperatures for 1 h. The resulting microstructures were analyzed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscatter diffraction and correlated with results of microhardness measurements. It was found that the microhardness first increases slightly upon annealing below the recrystallization temperature but then drops steeply at higher annealing temperatures due to the onset of recrystallization. Special emphasis was placed on how the microstructure evolves with respect to the radial and longitudinal position in the rod. Finally, a combination of swaging and heat treatment parameters were identified that can produce CoCrFeMnNi high-entropy alloys with a homogeneous composition and grain size and almost no texture. [ABSTRACT FROM AUTHOR]

The mechanical properties and thermal conductivity of W–1.0 wt%Y 2 O 3 (WY10) alloys prepared by spark plasma sintering (SPS) as well as ordinary sintering followed by swaging and annealing treatment, respectively, were investigated. The grains in the swaged WY10 are of round-bar shape with average diameter and length of 4.6 and 26.7 μm, respectively, which keep stable even after being annealed for 1 h at 1300 °C. The ductile–brittle transition temperature (DBTT) of swaged and annealed WY10 is about 200 °C, much lower than that of WY10 prepared by SPS method (∼500 °C). Annealing significantly improves thermal conductivity from 146 to 198 W/m K at room temperature. In addition, the total elongation is raised by 5.7 times than that of the unannealed one. The results indicate that the strength, ductility and thermal conductivity can be greatly improved by swaging and subsequent annealing. [ABSTRACT FROM AUTHOR]

Liquid phase sintering, heat treatment and swaging studies on three tungsten heavy alloys, 93W–4.9Ni–2.1Fe (wt%), 93W–4.2Ni–1.2Fe–1.6Co (wt%) and 93W–4.9Ni–1.9Fe–0.2Re (wt%) were carried out in detail with respect to microstructure, tensile and impact properties. All the alloys were sintered and swaged to 40% deformation. The results indicate that Re addition reduces the grain size of the alloy compared to W–Ni–Fe and W-Ni-Fe-Co alloys. W–Ni–Fe–Re alloy shows superior tensile properties in heat treated condition as compared to W–Ni–Fe and W–Ni–Fe–Co alloys. SEM study of fractured specimens clearly indicates that the failure in case of W–Ni–Fe–Re was due to transgranular cleavage of tungsten grains and W–W de-cohesion. W–Ni–Fe and W–Ni–Fe–Co alloys also failed by mixed mode failure. However, in these cases, ductile dimples corresponding the failure of the matrix phase was rarely seen. Thermo-mechanical processing resulted in significant changes in mechanical properties. While W–Ni–Fe–Re alloy showed the highest tensile strength (1380 MPa), W–Ni–Fe–Co exhibited the highest elongation (12%) to failure. A detailed analysis involving microstructure, mechanical properties and failure behavior was undertaken in order to understand the property trends. [ABSTRACT FROM AUTHOR]

A new process to produce ultrafine-grained reduced activation ferritic/martensitic steel was developed by cold-swaging and post-annealing. Microstructural examinations showed that the martensitic structures were broken into subgrain structures, and the rod-like carbides were fragmented after cold-swaging process with the cumulative strain of ~2.8. The tensile strength significantly increased accompanied by a reduction in the ductility in the cold-swaged samples, which was due to the insufficient strain hardening ability. After post-annealing at 973 K, a stable ultrafine-grained structure with uniformly distributed nanoprecipitates was obtained. The presence of uniformly distributed nanoprecipitates not only provided an effective precipitation strengthening but also improved the strain hardening ability, resulting in higher strength and better ductility than their as-tempered counterparts. [ABSTRACT FROM AUTHOR]

With the advantages of minimized stress concentration and allowing a combination of rotation and axial motion, internal helical splines have been widely used in automotive and aeronautic industries. However, this type of splines can only be manufactured using machining or extrusion method. This paper studied the recess swaging method, a net-shape forming process, for manufacturing the internal helical splines. In order to investigate the deformation tendency of workpiece along the thickness direction, Finite Element (FE) simulations and experiments were firstly performed on the recess swaging of tube without mandrel. Results show that the stress state in the forging zone is triaxial compressive except for the tensile axial stress at the inner surface of the tube. Moreover, during the recess swaging process material mainly flows along the axial and thickness direction, but the axial flow dominates. With increasing the reduction in outer radius and the wall thickness, metal flow along the axial direction increases but along the thickness direction decreases. Furthermore, based on the fundamental research on recess swaging experiments and FE simulations on the recess swaging method for manufacturing the internal helical splines were conducted. After the recess swaging, the hardness at the bottom of the tooth improved approximately 56.9%, while that at other zones increased 41%. The strength and the wear resistance of tooth were also improved. In summary, the recess swaging process provides an effective method for manufacturing the internal helical splines. [ABSTRACT FROM AUTHOR]

A new wire joining process for wires with sub-millimeter diameters applying the rotary swaging was investigated. The basic idea is to join two wire ends by a tube segment. In the study different material combinations using steel (AISI304) and copper (CW004A) were examined. Further the realization of a form-locked joint was investigated. The formed samples were tested by optical microscopy and tensile testing and compared to spot welded samples. [ABSTRACT FROM AUTHOR]

FE simulation was applied to study the material flow during infeed rotary swaging. The neutral plane according to the process parameters was investigated and compared with experimental results. A single forming stroke was analyzed precisely by using small time points of 10 -4 s. For analysis the essential steps between the first contact of wire and forging die and the last contact before the die opens again are represented. In that range the feed velocity is eliminated and the neutral plane can be observed as spatial velocity at nodes in the axial direction equal 0 mm/s. During a single stroke the location, the geometry and the orientation of the neutral plane is changing. [ABSTRACT FROM AUTHOR]

Microstructures and tensile properties of commercial pure magnesium processed by rotary swaging (RS) technique were investigated. Bulk and gradient textures in the RS processed Mg were characterised by neutron and synchrotron diffractions, respectively. Grains of the pure Mg were gradually refined with increase in the RS passes, which largely contributed to an increase in the tensile yield strength. A dominated basal fibre texture was observed in the RS processed pure Mg. Accommodated twinning deformation was also observed. Both the optical observations and texture analyses through the diameter of the swaged rod showed a gradient evolution in microstructure. [ABSTRACT FROM AUTHOR]

A new severe plastic deformation (SPD) process of "equal channel angular swaging" (ECAS) is developed by combining the conventional equal channel angular pressing with the incremental bulk metal forming method rotary swaging. The ECAS tool system contains four forming zones in a single forming pass. In the current study, the effect of the multi-stage forming process on both the strain distribution and the material deformation is investigated by means of finite element (FE) simulations and these simulations are verified with model experiments. The results serve as tool design guidelines for the ECAS process. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rotary swaging can be utilized as a joining by forming method for connecting tubes. [•] The concave arc joint type plays an important role on the joining strength of the tubes. [•] The joining strength of the tubes is high enough by rotary swaging. [Copyright &y& Elsevier]

The effect of heat treatment and swaging on microstructure and mechanical properties of a tungsten heavy alloy (WHA) of composition 90.5W-7.1Ni-1.65Fe-0.5Co-0.25Mo (wt%) has been examined in this study. The volume fraction and the contiguity of W-grains in the sintered microstructure decrease from 80% to 75% and 0.7 to 0.3, respectively, following an intermediate heat treatment comprising annealing at 1373 K followed by oil quenching. The average aspect ratio of W-grain increases with the increase in swaging deformation. While the bulk hardness of the alloy increases with increase in swaging deformation, a minor drop in hardness is observed following intermediate heat treatment. Peak broadening is observed in the X-ray diffractograms following thermo-mechanical processing with full width at half maxima (FWHM) of W110 peak exhibiting a similar trend as that of hardness. The as-sintered alloy exhibits low yield strength, tensile strength and very low elongation to failure. Subsequent thermo-mechanical treatment results in substantial improvement of both strength and elongation. A strength value of 1427 MPa with elongation of 5-6% has been achieved following 40% swaging. Work hardening behavior of the alloy in heat treated condition has been studied and the results are correlated with slip lines and dislocation behavior of the alloy. [ABSTRACT FROM AUTHOR]

The potassium doped tungsten (W-K) grade was achieved via swaging+rolling process. The swaged+rolled W-K alloy exhibited acceptable thermal conductivity of 159.1 W/mK and ductile-to-brittle transition temperature of about 873 K while inferior mechanical properties attributed to the coarse pores and small deformation degree. Then the thermal shock, fatigue resistance of the W-K grade were characterized by an electron beam facility. Thermal shock tests were conducted at absorbed power densities varied from 0.22 to 1.1 GW/m² in a step of 0.22 GW/m². The cracking threshold was in the range of 0.44-0.66GW/m². Furthermore, recrystallization occurred in the subsurface of the specimens tested at 0.66-1.1 GW/m² basing on the analysis of microhardness and microstructure. Thermal fatigue tests were performed at 0.44 GW/m² up to 1000 cycles and no cracks emerged throughout the tests. Moreover, recrystallization occurred after 1000 cycles. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical properties of ultra-fine grained materials are interesting for advanced engineering applications. For producing ultra-fine grained microstructures, various top-down processes of severe plastic deformation like equal channel angular pressing, high pressure torsion and accumulative roll bonding are available. The evolution of texture with respect to deformation by an alternative severe plastic deformation process, called accumulative swaging and bundling, is shown for ultra-fine grained Ti/Al composite wires, suitable for structural applications because of their high specific strength. In this cyclic process, an aluminium rod is inserted into a titanium tube before being swaged with an areal reduction of 20% per pass to a true strain of 4.3. After cleaning and cutting the resulting composite wire into 37 pieces, these are stacked in hexagonal arrangement into another Ti tube of the initial dimension before deformation is continued. The local texture gradient of the accumulative swaging and bundling composites was studied using a X-ray microdiffraction system based on a D8 Discover (Bruker AXS GmbH) equipped with a microfocus X-ray tube Iμ S and an area detector VÅNTEC-2000. The results are discussed with respect to the grain refining deformation process starting from the initial texture measured by synchrotron and neutron diffraction, respectively. The local Al and Ti texture evolution is related to the deformation mode, which is similar to extrusion. As such, an -double fibre and a -fibre emerge as the main texture components, each revealing gradients related to the deformation process. In particular, the local Al texture – being a function of both radial measurement position and deformation stage – can be correlated to material and process related issues like plastic flow and the superposition effect due to encapsulated filaments, respectively. [Copyright &y& Elsevier]

The effect of swaging on the microstructure and mechanical properties of 93W-4.9Ni-2.1Fe alloy was investigated. The alloy was prepared by liquid-phase sintering under hydrogen atmosphere followed by vacuum heat treatment and swaging at 600°C with different area reductions (ranging from 15.0% to 84.8%). The as-swaged alloy with area reduction 84.8% exhibits the highest ultimate tensile strength (about 1490MPa) and the lowest elongation (about 2.5%), which has been attributed to higher fraction of tungsten cleavage. For the as-sintered alloys, the fracture modes are a combination of the ductile rupture of W-Ni-Fe-Co matrix, transgranular cleavage of the tungsten particles, W-W interfacial segregation and W-M interfacial debonding, whereas transgranular cleavage of the tungsten particles is the main characteristic in the as-swaged alloy. Transmission electron microscopy images indicate that tungsten grains and W-Ni-Fe-Co matrix phase are composed of high-density dislocations. Based on the results, when running the swaging of 93W-4.9(Ni, Co)-2.1Fe alloy at 600°C, the strengthening mechanism can be mainly due to the working-hardening. [ABSTRACT FROM AUTHOR]

Highlights: [•] UFG of Al 1050 led to marked improvement of the corrosion resistance. [•] UFG resulted in more grain boundaries that enhance the formation of a stable passive film. [•] Corroded samples exhibited shallow rectangular pits. [•] UFG material revealed lower weight loss compared to as-received material. [Copyright &y& Elsevier]

Abstract: The effect of swaging on the Young's modulus of β Ti–33.6Nb–4Sn rods was investigated by X-ray diffraction, thermography, microstructural observations, deformation simulator analysis and cyclic tensile deformation. Stress-induced α″ martensite was stabilized by swaging, dependent on the diameter reduction rate during swaging. Thermography and deformation simulator analysis revealed that swaged rods were adiabatically heated, and consequently, stress-induced α″ underwent reverse transformation. Young's modulus, which was measured by the slope of the initial portion of the stress–strain curve, decreased from 56GPa in the hot-forged/quenched rod to 44GPa in the rapidly swaged rod with a high reduction rate and to 45GPa in the gradually swaged rod with a low reduction rate. The tangent modulus, which was measured by the slope of the tangent to any point on the stress–strain curve, decreased with strain even in the linear range of the stress–strain curve of the hot-forged/quenched rod and the rapidly swaged rod, while the tangent modulus remained unchanged for the gradually swaged rod. It was found that Young's moduli in swaged β Ti–33.6Nb–4Sn rods were affected by stabilized α″ martensite. Low Young's modulus of 45GPa and high strength over 800MPa were obtained when the reverse transformation by adiabatic heating was suppressed and the stress-induced α″ was sufficiently stabilized by gradual swaging to a 75% reduction in cross section area. [Copyright &y& Elsevier]

Abstract: The objective of this study was to investigate the effect of swaging on the microstructure and tensile properties of high density two phase alloys 90W–7Ni–3Fe and 93W–4.9Ni–2.1Fe. Samples were liquid phase sintered under hydrogen and argon at 1480°C for 30min and then 15% cold rotary swaged. Measurement of microstructural parameters in the sintered and swaged samples showed that swaging slightly increased tungsten grain size in the longitudinal direction and slightly decreased tungsten grain size in the transverse direction. Swaging increased the contiguity values in both longitudinal and transverse directions. Swaging led to more severe deformations at the edges than at the center of the specimens. Solidus and liquidus temperatures of the nickel-based binder phase in the sintered and swaged samples were determined by differential scanning calorimetry measurements. An increase in tensile strength with a reduction in ductility was observed due to strain hardening by swaging. [Copyright &y& Elsevier]

Abstract: Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre. [Copyright &y& Elsevier]

Abstract: This paper describes the effect of tungsten content on microstructure and mechanical properties of swaged Co-containing tungsten heavy alloys with varying tungsten (90W–7Ni–2Fe–1Co, 93W–4.9Ni–1.4Fe–0.7Co and 95W–3.5Ni–1Fe–0.5Co). With increasing tungsten while tensile strength goes through a maximum, both percent elongation and impact energy decrease. Microstructure and fractographic analyses have been carried out in order to explain the trends in mechanical properties. Predominant transgranular fracture of tungsten grains combined with ductile dimple failure of the matrix in 90% W alloy is responsible for superior properties of this alloy in comparison to the alloy with 95% W. The highest tensile strength attained in 93% W alloy is attributed to predominant cleavage failure of W-grains. The results clearly indicate that the matrix volume fraction, contiguity and matrix mean path greatly influence the mechanical properties of tungsten heavy alloys. [Copyright &y& Elsevier]

Abstract: Body centred cubic (BCC) β-phase multifunctional titanium alloys have been developed with a very unique combination of thermal and mechanical properties. In this investigation, a very low porosity Ti–36.8–Nb–2.7Zr–2.0Ta–0.44O (wt%) alloy was produced by powder sintering, hot forging, solution treatment and cold swaging. X-ray diffraction and transmission electron microscopy (TEM) of the solution treated alloy revealed the presence of a small amount of ω-phase in a predominantly BCC β-phase matrix. Electron backscatter diffraction (EBSD) of the swaged alloy revealed a highly elongated and fragmented microstructure, and a strong 〈110〉 fibre texture. TEM also revealed the existence of stress-induced twin lamella, dislocations and ω-phase. Consistent with previous studies on these types of alloys, the swaged alloy exhibited non-linear elasticity during tensile straining, low elastic modulus (45.4GPa), high elastic limit (2.3%), high elongation to failure (8.1%), and a high yield strength (880MPa) and tensile strength (940MPa). The coefficient of thermal expansion was also low (∼5×10−6 K−1 between 50 and 300°C) in this alloy. [Copyright &y& Elsevier]

Abstract: The current work presents a simulation and experimental study on the formation characteristics of sinking thin-walled copper tube with axially inner micro grooves (TCTAIG) through radial forging. A finite element (FE) model is established. The deformation of grooves, distribution of equivalent stress and strain, and the effects of process parameters are analyzed using a FE software. Experiments with the same parameter settings are compared with the simulations. The axial elongation and radial shrinkage of TCTAIG can be obtained. The grooves are twisted as helical lines in the sinking zone. The metal flows axially and tangentially. The maximal equivalent stress and strain occur at the bottom of the grooves. The equivalent strain increases as the step increases, and finally stays at a certain value: bottom of grooves, 0.9; outer surface, 0.8; and top of teeth, 0.3. The equivalent strain becomes more uniform, the force of dies reduces, and the elongation ratio decreases with increasing feed speed. The equivalent stress, force of dies, and axial pushing force increases rapidly with increasing shrinkage rate. Apparent collapse occurs and the surface quality of the forged part becomes worse at a low feed speed or a shrinkage rate of 50%. [Copyright &y& Elsevier]

Abstract: The microstructure evolution and change in mechanical properties of commercially pure aluminum (Al 1050) were investigated during severe plastic deformation by rotary swaging (RS) at ambient temperature. Optical microscopy (OM) and scanning electron microscopy (SEM) using electron back scatter diffraction (EBSD) were utilized to document the evolution of the microstructure. Hardness and tensile tests were conducted to characterize mechanical properties. Rotary swaging was found to lead to a marked decrease in grain size. The microstructure consisted of cell structure of low angle grain boundaries (LAGBs) within bigger grains. After heavy swaging to true deformation degree of φ=3, the microstructure was quite uniform normal to flow direction in terms of cell size, average misorientation angle and content of low angle grain boundaries. Extremely fine dynamically recrystallized grains, heterogeneously nucleated at existing grain boundaries were evident on the section parallel to the flow direction. As compared to the as-received condition, the yield stress and ultimate tensile strength of the material was strongly increased by a factor of 8 and 2.3, respectively. Furthermore, the elongation to fracture was drastically reduced as was the uniform strain indicating a marked reduction in work hardening capability. [Copyright &y& Elsevier]

Abstract: The microstructural influence on fracture behavior of tensile and Charpy impact toughness properties were investigated for 90Wyph name="sbnd" />2Fe0Wyph name="sbnd" />2Feglyph name="sbnd" />0.5Co tungsten heavy alloys, which are in use of kinetic energy penetrators. The alloys were sintered, heat treated and swaged with 40% reduction in area. Both microstructure and mechanical properties were sensitively dependent on the alloy composition. The Wph name="sbnd" />Feexhibited increased tensile strength, ductility and impact toughness compared to the Wph name="sbnd" />Mo alloy. Fractographic study revealed that the mode of tensile failure changes from flat to sheared tungsten grains for low to high strength tungsten heavy alloys, whereas the fracture behavior changes from flaws/cracks to transgranular cleavage of tungsten grains for low to high Charpy impact toughness alloys. The results indicate that a strong relationship between microstructure, fracture behavior, tensile and impact properties as a function of alloy composition. [Copyright &y& Elsevier]

Abstract: The aim of this study was to investigate the effect of swaging on the microstructure and mechanical properties of vacuum sintered 90W–7Ni–3Fe alloys. Cold isostatically pressed samples were sintered under vacuum at 1510°C, for 30min. Samples were then 15% cold rotary swaged. The study has shown that, mechanical properties of relatively low density (<98% theoretical) liquid phase sintered 90W–7Ni–3Fe alloy can be considerably improved by swaging due to increase in density and strain hardening. [Copyright &y& Elsevier]

Abstract: The effect of swaging deformation and low temperature aging on mechanical properties of tungsten heavy alloy (90W–6Ni–2Fe–2Co) was studied. The alloy was prepared by conventional hydrogen sintering followed by vacuum heat treatment and swaging with varying reductions in area (ranging from 10 to 75%). The swaged samples were aged in nitrogen atmosphere at temperatures ranging from 300 to 1100°C followed by microstructure and mechanical property evaluation. Both microstructure and mechanical properties were sensitively dependent on the amount of deformation imparted during swaging. Subsequently, aging also influenced the properties depending upon the aging temperature. Detailed fractographic study revealed that the fracture mode of the alloy changed from intergranular to transgranular mode depending upon thermo-mechanical processing. Aging treatment after swaging affected the fracture morphology of alloy considerably. Samples aged at 500°C showed predominant transgranular failure of tungsten grains, whereas the one heat treated at 700°C showed increasing evidence ductile tear. Based on the results, an approach for optimizing mechanical properties that involves heat treatment and swaging operation was proposed. [Copyright &y& Elsevier]

Abstract: Swaging is a cold working process involving plastic deformation of the work piece to change its shape. A swaged joint is a connection between two components whereby a swaging tool induces plastic deformation of the components at their junction to effectively bind them together. This is commonly used when welding or other standard joining techniques are not viable. Swaged joints can be found for example, in nuclear fuel assemblies to connect the edges of thin rectangular plates to a supporting structure or frame. The aim of this work is to find a model to describe the vibrational behaviour of a swaged joint and to estimate its strength in resisting a longitudinally applied load. The finite element method and various experimental rigs were used in order to find relationships between the natural frequencies of the plate, the joint stiffness and the force required to shift the plate against the restraining action of the swage connection. It is found that a swaged joint is dynamically equivalent to a simple support with the rotation elastically restrained and a small stiffness is enough to resist an important load. [Copyright &y& Elsevier]