放电等离子烧结制备W-ZrC/HfC-Re合金的力学性能和热稳定性研究

Mechanical properties and thermal stability of W-ZrC/HfC-Re alloys fabricated by spark plasma sintering

摘要:

采用机械球磨和放电等离子烧结法（SPS）制备了W-0.5wt.%ZrC-(1, 3)wt.%Re（WZC1R，WZC3R）和W-0.5wt.%HfC-(1, 3)wt.%Re（WHC1R，WHC3R）四种钨基材料，并对其微结构、力学性能和高温稳定性进行了测试与分析。WZC3R合金在500 ℃时的极限抗拉强度（UTS）高达728 MPa，600 ℃时UTS维持653 MPa，比SPS制备的纯W提升近2.1倍。弥散分布的纳米尺寸ZrC颗粒起到钉扎晶界和位错的作用，提升材料强度，此外抑制晶粒粗化带来细晶强化。WHC3R在400 ℃时，其延伸率为13.9%，韧脆转变温度（DBTT）介于300 和400 ℃，比SPS制备的W-ZrC和纯W分别降低200 ℃和300 ℃。固溶元素Re通过增加可动滑移面的数量，降低引发塑性变形所需的临界应力，从而改善钨材料的韧性。SPS制备的四种钨基材料展现出优异的热稳定性，1600 ℃真空退火1小时后，试样的晶粒尺寸和维氏显微硬度均未显著变化。其原因是Re溶质原子使钨产生晶格畸变，抑制高温下钨原子的扩散，阻碍晶界迁移，减缓钨晶粒粗化的动力学过程，从而提升材料的高温稳定性。

Abstract:

Four kinds of tungsten-based materials, W-0.5 wt.%ZrC-(1, 3) wt.%Re (WZC1R, WZC3R) and W-0.5 wt.%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 °C and an UTS of 653 MPa at 600 °C, respectively, which are about 2.1 times higher than 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 coarsing. The WHC3R exhibits a total elongation (TE) of 13.9% at 400 °C, and its DBTT is in the range of 300 ~ 400 °C, which is about 200 and 300 °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 °C. The Re element solidly dissolved in W leads to lattice distortion, which 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.