高压扭转对难熔金属粉末组织致密及强化的影响

Effects of High-Pressure Torsion on Dense Compact and Strengthening of Refractory Powder

采用高压扭转法在350℃下将纯钼粉末直接制备成致密体材料。用金相显微镜、显微维氏硬度计、扫描电镜和X射线衍射仪分析高压扭转过程中粉末颗粒孔隙闭合及性能强化规律。结果表明:高压扭转后钼颗粒粉末在剪切力作用下通过移动和变形相互啮合联结,颗粒间大块链状孔隙逐渐缩小、闭合,此时颗粒间界面结合较好;高压扭转前后材料内部亚晶尺寸由59.8 nm细化到46.9 nm,微观应变由1.04×10^(-4)增大到1.12×10^(-3);晶粒细化和微观应变增大引起的晶格缺陷会促进晶粒内部位错增殖、缠结来强化基体。

Pure molybdenum powder was directly compacted into the dense body material by high-pressure torsion（HPT） at 350 °C. The effects of HPT on pore closure and performance strengthening of the powder particle were investigated by optical telescope, microhardness-testing device, scanning electronic telescope and X-ray diffractometer. The results indicate that the molybdenum powder mechanical mesh each other by particles movement and deformation under shear force; at this time the interface bonding performance is better, the large chain pores in particles are welded effectively after high-pressure torsion. In the HPT process the subgrain size decreases from 59.8 nm to 46.9 nm, the micro strain increases from 1.04×10^（-4） to 1.12×10^（-3）. The lattice defects caused by grain refinement and micro strain can promote dislocation multiplication and tangling to strengthen the matrix.