W粉粒度对Ti-20%W合金组织和力学性能的影响

以TiH2粉和不同粒径的W粉为原料,通过粉末冶金法制备了Ti-20%W合金,利用金相显微镜、X射线衍射仪、扫描电子显微镜和能谱分析仪对合金的微观组织和成分进行分析,并测定了其显微硬度和抗压强度。结果表明:选用细W粉时,W颗粒与Ti固溶量大,显微硬度值均匀且抗压强度高,强化机理为固溶强化,断口分析表明采用纳米W粉时Ti-20%W合金发生了韧性断裂;而采用粗W粉时,W颗粒与Ti固溶量较少,显微硬度值从W颗粒中心到Ti基体呈现先升高后降低的趋势,抗压强度较差。这说明采用W增强Ti基体时固溶强化比第二相即颗粒强化的效果更明显。

Effect of W powder size on the microstructure and mechanical properties of Ti-20wt%W alloy

Blends of TiH_2 and W powders were consolidated by powder metallurgy, using an initial W powder size that was very fine (50～70nm and 6～8μm) or very coarse (<30～35μm). Microstructure and component were analyzed by optical micrographs (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS).The microhardness and compression strength were also measured. The results show that dissolution of W powders in the Ti matrix during consolidation is almost complete for the fine powders, which exhibit much higher strength of compression and the distribution of microhardness value is uniform. The strengthening mechanism for those alloys is the solid-solution strengthening. The fracture analysis indicates that Ti-20wt% W alloy prepared by nano W powders displays tough fracture. When using coarse W powder, dissolution of W powders in the Ti matrix is limited and the microhardness presents a trend of first increase then decrease from the center of W powder to Ti matrix whose strength of compression is lower. This indicates that tungsten strengthened titanium is due to solid-solution strengthening rather than second phase strengthening.