Phase equilibria effects on the enhanced liquid phase sintering of tungsten- copper

High hardness and wear resistance of W-Cu composites achieved by elemental dissolution and interpenetrating nanostructure

The effects of aluminum (Al) on the microstructure, hardness and wear resistance of tungsten-copper (W-Cu) composites were investigated. The W-Cu composites were fabricated via mechanical alloying and spark plasma sintering. It is found that the Al dissolved in the metastable W-Cu alloy can act as an 'intermediary' to hinder the diffusion and phase separation process of Cu out of W during sintering, constructing an interpenetrating nanostructure where Al redistributes in W and Cu. Correspondingly, the hardness of composites increase from 463.4 HV₃₀ to 512.05 HV₃₀ due to Al dissolution and formation of the nanostructure, and their contributions to hardness variation of the original W and Cu regions were distinguished by nanoindentation. In addition, the wear volume was also reduced to less than a third of that of original W-Cu composites without Al addition due to the abundant interfaces and mechanical strengthening, which restricts the removal of W and propagation of cracks during the wear process.

Strain-stress relationship and dislocation evolution of W-Cu bilayers from a constructed n-body W-Cu potential

An n-body W-Cu potential is constructed under the framework of the embedded-atom method by means of a proposed function of the cross potential. This W-Cu potential is realistic to reproduce mechanical property and structural stability of WCu solid solutions within the entire composition range, and has better performances than the three W-Cu potentials already published in the literature. Based on this W-Cu potential, molecular dynamics simulation is conducted to reveal the mechanical property and dislocation evolution of the bilayer structure between pure W and W0.7Cu0.3 solid solution. It is found that the formation of the interface improves the strength of the W0.7Cu0.3 solid solutions along tensile loading perpendicular to the interface, as the interface impedes the evolution of the dislocation lines from the W0.7Cu0.3 solid solutions to the W part. Simulation also reveals that the interface has an important effect to significantly reduce the tensile strength and critical strain of W along the tensile loading parallel to the interface, which is intrinsically due to the slip of the edge or screw dislocations at low strains as a result of the lattice mismatch.

Powder Metallurgy Processing of a WxTaTiVCr High-Entropy Alloy and Its Derivative Alloys for Fusion Material Applications

The W_xTaTiVCr high-entropy alloy with 32at.% of tungsten (W) and its derivative alloys with 42 to 90at.% of W with in-situ TiC were prepared via the mixing of elemental W, Ta, Ti, V and Cr powders followed by spark plasma sintering for the development of reduced-activation alloys for fusion plasma-facing materials. Characterization of the sintered samples revealed a BCC lattice and a multi-phase structure. The selected-area diffraction patterns confirmed the formation of TiC in the high-entropy alloy and its derivative alloys. It revealed the development of C15 (cubic) Laves phases as well in alloys with 71 to 90at.% W. A mechanical examination of the samples revealed a more than twofold improvement in the hardness and strength due to solid-solution strengthening and dispersion strengthening. This study explored the potential of powder metallurgy processing for the fabrication of a high-entropy alloy and other derived compositions with enhanced hardness and strength.