Mechanical Properties and Thermal Stability of W- ZrC/HfC-Re Alloys Fabricated by Spark Plasma Sintering

Four kinds of tungsten-based materials, W- 0.5wt%ZrC-(1, 3)wt%Re ( WZC1R, WZC3R) and W-0.5wt%HfC-(1, 3)wt%Re (WHC1R, WHC3R) were prepared by mechanical ball milling and spark plasma sintering (SPS). The microstructures, mechanical properties and thermal stability were investigated. The WZC3R alloy exhibits a high ultimate tensile strength ( UTS) of 728 MPa at 500 degrees C and an UTS of 653 MPa at 600 degrees C, which are about 2.1 times higher than that of SPSed pure W. The uniformly distributed nano- sized ZrC and HfC particles can pin the grain boundaries and dislocations, thereby increasing the strength and inhibiting grain coarsening. The WHC3R exhibits a total elongation of 13.9% at 400 degrees C, and its DBTT is in the range of 300-400 degrees C, which is about 200 and 300 degrees C lower than that of SPSed W-ZrC and pure W, respectively. The addition of the solid solution element Re improves the toughness of W materials by increasing the number of available slip planes and reducing the critical stress needed to start plastic deformation. In addition, the four alloys show excellent high-temperature stability with no significant change in grain size and Vickers microhardness even after heat treatments at temperatures reach up to 1600 degrees C. The Re element solidly dissolved in W leads to lattice distortion; it can inhibit the diffusion of W atoms at high temperatures, hinder the migration of grain boundary, and slow down the kinetic process of W grain coarsening, thus enhancing the high-temperature stability of the W materials.