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This paper analyzes the configurations of the binding phases at different temperatures for 95W–5(Ni/Fe/Co) alloys by TEM, the precipitates of 95W–5(Ni/Fe/Co) alloys distribute dispersively at 300–500 °C. So, it can make up for the fall of strength caused by the rise of temperature. Deformed at 600 °C, the plasticity of the binding phases falls when the precipitates grow into stripes and distribute layer upon layer. Furthermore, owing to the discordance of the expansion coefficients of the two phases, internal stress forms, which reduces the integration strength at the boundary. The abnormity of plasticity change has close connection with temperature and precipitation. [Copyright &y& Elsevier]

Abstract: Hot-hydrostatic extrusion of a liquid-phase sintered 93W–4.9Ni–2.1Fe alloy was performed at 1200°C with various extrusion ratios from 2.5:1 to 4:1, and the microstructure and mechanical properties of the as-extruded alloy were experimentally investigated in detail. It was shown that the microstructure of the as-extruded alloy was characterized by elongated tungsten particles with cellular sub-structures consisting of high-density dislocations embedded in a binding Ni–Fe–W matrix phase with fine dynamically re-crystallized grains. In comparison with the as-sintered alloy, the as-extruded alloy presented a much higher tensile strength (e.g., as high as 1540MPa with an extrusion ratio of 4:1) and a relatively lower but reasonable ductility, with the strength increment and ductility decrement being in proportion to the extrusion ratio. The increase in tensile strength can be attributed to the higher aspect ratio of the elongated tungsten particles as well as the unique cellular sub-structures formed in the tungsten particles, while the decrease in ductility is related to the less ability of the matrix phase between the elongated tungsten particles to accommodate deformation and to inhibit crack propagation before tungsten cleavage failure. [Copyright &y& Elsevier]

Abstract: The process of repetitive upsetting-extrusion (RUE) was used to achieve severe plastic deformation, and its validity in preparing bulk ultrafine-grained materials was demonstrated by experimental investigation on a LY12 Al alloy. The results showed that the microstructure evolution of the alloy due to RUE processing was of a three-step character. With the increase of the RUE processing passes, i.e., the increase of the accumulated true strain, the grain size of the alloy gradually decreased, while the compressive yield stress, σ 0.2, and the micro-hardness, H v, increased correspondingly. In particular, after 10 passes of RUE processing corresponding to an approximate accumulated true strain of 8.926, an equiaxed ultrafine microstructure with an average grain size of about 200nm was obtained. As a consequence, the σ 0.2 and H v of the alloy were enhanced from the starting 318.5MPa and 112.3 H v to 513.6MPa and 176.5 H v, respectively. The results also showed that the Hall–Petch relationship persists for the RUE-processed LY12 Al alloy with ultrafine grains down to 200nm. [Copyright &y& Elsevier]

The hydrogen storage properties of nanocomposite Mg–2Ni–2Cu–1CrCl3 (wt.%) prepared by mechanical alloying have been investigated. The ball milling process was performed under hydrogen atmosphere. During the ball milling process, the composite Mg–2Ni–2Cu–1CrCl3 can absorb hydrogen. When the ball milling time exceeds 110 h, the composite can absorb hydrogen completely (to its maximum). The nanocomposite has remarkable kinetics of hydriding/dehydriding process, for example, the nanocomposite milled for 110 h can absorb 5.5 wt.% hydrogen at 200 °C or 6.2 wt.% at 250 °C in 60 s under 2.0 MPa hydrogen pressure, and its desorption capacity also exceeds 6.3 wt.% in 700 s at 320 °C under 0.1 MPa. The influences of ball milling times on hydrogen storage properties were investigated. The catalytic effect of CrCl3 on the hydriding and dehydriding process was also discussed. [Copyright &y& Elsevier]

The microstructure and mechanical properties of the rapidly solidified 2024 aluminum alloy consolidated by hot hydrostatic extrusion were experimentally investigated, with special emphasis on finding out the influence of both the two main consolidation parameters, extrusion ratio and temperature, and the solution-aging treatments on the mechanical properties of the alloy. The results show that the optimal extrusion temperature for the consolidation of the alloy powders is 430–450 °C, and that the extrusion ratio should not be less than 21:1. By solution treatment at 495 °C for 1.5 h and subsequent aging at 190 °C for 5 h, peak age hardening occurs for the alloy consolidated by using the above as-optimized processing parameters, with the yield strength σs and ultimate tensile strength σb of the alloy reaching as high as about 460 and 540 MPa respectively. Meanwhile, the tensile elongation of the peak-aged alloy remains at more than 10%. Transmission electron microscopy observation reveals that the as-consolidated alloy is characterized by a very fine recrystallization structure with submicron-sized grains, and that the grain growth of the consolidated alloy during subsequent solution treatment is quite limited. Peak-aging of the solution-treated alloy gives rise to lots of homogeneously distributed nanometer-sized S′ precipitates. The high mechanical strength of the alloy can be attributed to the very fine grain structure and the precipitation of the supersaturated solute elements in the form of homogeneously distributed nanometer-sized S′ precipitates. [Copyright &y& Elsevier]

Abstract: A TiAl-based alloy with nominal composition of Ti–36wt.% Al was prepared by a mechanical milling and reactive sintering route consisting of three basic steps: (1) mechanical milling of blended elemental Ti and Al powder mixture, (2) densification and consolidation of as-milled Ti/Al composite powder compact via warm extrusion, and (3) subsequent reactive sintering of as-extruded powder billet. The microstructure of the as-sintered TiAl alloy samples was observed by optical microscopy (OM) and transmission electron microscopy (TEM), respectively. The mechanical properties were measured by compression tests performed at room and elevated temperatures up to 800°C. The results show that mechanical milling before reactive sintering is very effective in microstructure refining of reactively synthesized TiAl alloy. The TiAl alloy sintered from 1h milled Ti/Al composite powders presented a homogeneous γ/(α2 +γ) duplex microstructure with very fine grains of 5–10μm and good mechanical properties. On the basis of microstructure observation and compressive stress–strain relationship, the deformation mechanism at different temperature was discussed. [Copyright &y& Elsevier]