In this work, copper–tungsten (Cu-W) composites with a cubic and rhombic dodecahedron W-skeleton were fabricated by the infiltration of Cu melt into a three-dimensionally printed W scaffold. The effects of the skeleton structure on the mechanical properties and energy-absorbing characteristics of the Cu-W interpenetrating-phase composite were investigated and compared with those of commercial Cu-W composite fabricated by powder metallurgy. The results indicated that the mechanical properties of the studied Cu-W interpenetrating-phase composites were mainly related to the properties of their ordered skeletons. Compared to the dodecahedron W-skeleton Cu-W composites, cubic-W-skeleton Cu-W composites exhibited higher strengths but lower absorbed energy. The Cu-W composites with ordered W-skeletons displayed much higher energy absorption than the commercial Cu-W ones. By adjusting the ordered W-skeleton structure contained in the composite, the strength and deformation behavior of the Cu-W composite can be effectively improved, which provides a guide to optimizing the mechanical properties and energy absorption of Cu-W composites.

In this study, the Fe-16Mn-9Al-0.8C-3Ni (wt.%) lightweight steel was fabricated by novel twin-roll strip casting technology. The microstructure, tensile properties and strain-hardening behavior of the present steel have been investigated and compared to those of conventionally processed steels with similar chemical compositions. After annealing, a unique gradient microstructure of intermetallic compound (B2)-austenite was obtained along the thickness direction, consisting of granular B2 (average: 430 nm) and fine austenite (average: 1.82 μm) at the surface layer, blocky B2 (average: 1.03 μm) and medium austenite (average: 3.98 μm) at the quarter layer and polygonal B2 (average: 1.94 μm) and coarse austenite (average: 6.13 μm) at the center layer. The cooperative action of B2 pinning dislocation, plane slip and back stress led to stronger strain hardening, among which the strong back stress effect originated from the multistage discontinuous austenite deformation and the mechanical incompatibility between austenite and B2 is believed to be the most important reason, thereby achieving an excellent balance of strength (ultimate tensile strength: 1147 MPa) and ductility (total elongation: 43.2%). This work not only developed a new processing way to fabricate Ni-containing Fe-Mn-Al-C lightweight steel with outstanding mechanical properties, but also provided a potential solution for manufacturing some other metallic materials accompanied by brittle B2 intermetallic.

An equimolar AlCoCrFeNi high-entropy alloy (HEA) with trade-off properties between strength and ductility is prepared by hot extrusion for the first time. Compared with the HEAs prepared by casting and heat treatments, hot-extruded AlCoCrFeNi HEA not only contains uniform elements and phase distributions but also finer grains and microstructures. The average diameter of the homogeneous equal-axis fine grains is less than 5 µm. The compressive yield strength and ultimate compressive strength of the hot-extruded AlCoCrFeNi HEA reach 1450 and 3500 MPa respectively, while the compressive strain reach 42%. These excellent mechanical properties are attributed to the fine microstructure. In addition, the uniform dispersed network phase structures, ultrafine sub-grains, high density dislocations and blunted cracks in the deformed AlCoCrFeNi HEA are all the important factors affecting the strength and plasticity of the HEA. Hot-extruded AlCoCrFeNi HEA with excellent mechanical properties confirms a great prospect for the preparation of high-strength HEAs.

High-temperature heat treatments can improve the element distributions and phase structures of AlCoCrFeNi high entropy alloys (HEAs). However, the long-term isothermal annealing at high temperatures will make the grains grow crazily. In this study, the problem of grain growth caused by high-temperature annealing at 1200 °C was solved by heavily deformed AlCoCrFeNi HEAs. The ultrafine grains formed by dynamic recrystallization will grow firstly during the subsequent annealing process, which inhibits the increase in the larger grains in the hot-extruded AlCoCrFeNi HEAs. The effect of high-temperature annealing on hot-extruded AlCoCrFeNi HEAs was also explored simultaneously in detail. After annealing at 1200 ℃ for 2 h, the compressive strength and fracture strain of the AlCoCrFeNi HEA reached an astonishing result of 3750 MPa and 43%, respectively. The results are attributed to the skeleton-liked FCC structures deeply interspersed into the grains and more importantly, the fine annealed grains which still maintained an average diameter of 20 μm. Additionally, the new nano-precipitates did not expand wildly at high temperatures either. Research on heavily deformed AlCoCrFeNi HEAs isothermally annealed at 1200 °C provides an available idea for further improving the properties of these HEAs.