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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]

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]

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 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]

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]

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]

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]

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 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 work objective was focused on investigation of deformation behaviour of NiTi-based shape memory alloys with respect to technology of their preparation. Deformation behaviour was assessed by unconventional forming methods, particularly by equal channel angular extrusion (ECAE)—but in combination with preceding rotary forging (swaging). Classical light microscopy, as well as X-ray diffraction, was used for evaluation of structural framework of castings and of material after forming. It was established that the alloy Ni50.6–Ti (at.%) after ECAE and re-crystallisation annealing shows bi-modal distribution of mosaic blocks, i.e. mosaic blocks larger than 10μm and blocks smaller than 10μm. For determination of re-crystallisation temperature in deformed materials 7 modes of heat treatment were applied. It was proven that the temperature of 600°C was the starting temperature that initiated re-crystallisation. [Copyright &y& Elsevier]

Abstract: The present work shows how the microstructure and the phase transformation behavior of as-cast Ti-48 at.% Ni-2 at.% Fe shape memory alloys respond to different thermomechanical treatments. The applied procedures involve homogenization, swaging at different temperatures and recrystallization annealing. The as-cast material is characterized by a coarse-grained microstructure. During repeated hot working in combination with recrystallization treatments, a fine-grained microstructure evolves in the surface volume of the swaged Ni–Ti–Fe rod. In contrast, its center remains almost unaffected by recrystallization (because less dislocations are introduced during swaging and recovery processes are more intense). This type of microstructural heterogeneity can be avoided by cold work at the end of the thermomechanical procedure. Swaging at low temperatures results in higher dislocation densities and thus in a more homogeneous microstructural evolution during recrystallization. In the cold-worked state, the phase transition R→B19′ is strongly impeded by the presence of dislocations, whereas the transition characteristics of the recrystallized and of the non-deformed original material state almost coincide. [Copyright &y& Elsevier]

Using high-energy ball milling, nanosized thoria powders were obtained. After mixing the thoria nanoparticles with tungsten powders, a nanocomposite cathode was fabricated by sintering and hot swaging. The relative density of the nanocomposite material is near 100%. The microstructure of the nanocomposite cathode is quite different from that of conventional thoriated tungsten cathodes. Most of the thoria particles in the nanocomposite are less than 100 nm in diameter, and situated on the boundaries of tungsten grains. The nanocomposite cathode shows a much lower arc initiation field than that of conventional cathode, which will improve the performance of the cathode significantly. [Copyright &y& Elsevier]