Effect of Aging Time on Microstructure and Properties of Cold-Rolled Ni-W-Co-Ta Medium-Heavy Alloy

A systematical exploration of the effect of aging time on the microstructure and mechanical properties of cold-rolled Ni-W-Co-Ta medium-heavy alloy with 90% thickness reduction at the aging temperature of 700 degrees C was performed. The results demonstrate that the volume fraction of the precipitation (Ni4W), which persists under various aging times, increases from 13.7% (2 h) to 28.7% (32 h) with the extension of aging time. Meanwhile, the microstructure after aging treatment is still dominated by dislocation entanglement and dislocation walls, although the degree of lattice distortion and dislocation density attributed to heavy deformation decreases. The maximum tensile strength, yield strength, and microhardness (2286 MPa, 1989 MPa, 766 HV) of the cold-rolled Ni-W-Co-Ta medium-heavy alloy under the 16 h aging treatment at 700 degrees C are reached, respectively. The ductile-brittle mixed fracture morphology is maintained in the fracture morphology of the medium-heavy alloy before and after aging treatment.