Effect of quenching temperature on the microstructure evolutions and strength-ductility of W-Ni-Cu alloy at room-temperature and cryogenic

Abstract

Tungsten (BCC phase) exhibits distinct ductile-to-brittle transition characteristics. As temperature decreases, brittleness increases, ductility decreases, significantly limits its engineering applications. Here, W-5Ni-2Cu alloy was prepared by powder metallurgy, and the effect of different quenching temperatures on its microstructure evolution and mechanical properties at room-temperature and cryogenic. According to the results, rapid quenching can significantly improve the strength-ductile of W-5Ni-2Cu, especially the cryogenic properties. After quenching at 1200 °C, the strength-ductility of W-5Ni-2Cu from room temperature to −43 °C did not deteriorate, and compared with the sintered alloy, the tensile strength and elongation were increased by 7.3% and 13.0% at room-temperature, and by 16.0% and 100.0% at cryogenic. The appropriate quenching temperature can effectively refine the W grain size, reducing the WW continuity and dihedral angle, while the quenching temperatures reaches 1300 °C, it will cause abnormal W grain growth and deteriorate the mechanical properties. Furthermore, rapid quenching changes the fracture mode from intergranular fractures to transgranular fractures. Especially, the W- 〈111〉∥γ-〈110〉 preferential orientation relationship is obviously improved at −43 °C, increasing the interfacial bonding strength and co-deformation ability of W-γ phase, thereby slowing down the hardening rate and increasing the strength and elongation.