Effect of swaging on microstructure and mechanical properties of liquid-phase sintered 93W-4.9(Ni, Co)-2.1Fe alloy

The effect of swaging on the microstructure and mechanical properties of 93W-4.9Ni-2.1Fe alloy was investigated. The alloy was prepared by liquid-phase sintering under hydrogen atmosphere followed by vacuum heat treatment and swaging at 600 °C with different area reductions (ranging from 15.0% to 84.8%). The as-swaged alloy with area reduction 84.8% exhibits the highest ultimate tensile strength (about 1490 MPa) and the lowest elongation (about 2.5%), which has been attributed to higher fraction of tungsten cleavage. For the as-sintered alloys, the fracture modes are a combination of the ductile rupture of W-Ni-Fe-Co matrix, transgranular cleavage of the tungsten particles, W-W interfacial segregation and W-M interfacial debonding, whereas transgranular cleavage of the tungsten particles is the main characteristic in the as-swaged alloy. Transmission electron microscopy images indicate that tungsten grains and W-Ni-Fe-Co matrix phase are composed of high-density dislocations. Based on the results, when running the swaging of 93W-4.9(Ni, Co)-2.1Fe alloy at 600 °C, the strengthening mechanism can be mainly due to the working-hardening.