高压扭转制备难熔金属Mo的微观结构及性能分析

Analysis of Microstructure and Properties of Refractory Metal Molybdenum Prepared by High-pressure Torsion

以难熔金属纯Mo粉末为原料,采用高压扭转工艺在350℃温度和1.5GPa压力下制成相对密度为96.45%的金属Mo坯,利用多种检测手段分析了高压扭转过程中Mo粉颗粒孔隙演变及致密强化规律。探讨了预压Mo坯高径比对压扭Mo坯微观结构及性能的影响。结果表明,高径比越小,材料等效剪切应变量越大,压扭Mo坯相对密度、硬度值越高,其内部亚晶尺寸细化及微观应变积累越明显。当高径比从0.5降至0.3时,由晶粒细化及应变积累引起的位错密度可从1.67×10^(14) m^(-2)提高到3.03×10^(14) m^(-2)。

Using the refractory powders of pure molybdenum as raw material, the molybdenum billet with relative density of 96.45% was prepared by high-pressure torsion at 350 ℃ temperature and 1.5 GPa pressure. The rules of pore evolution and densification strengthening were analyzed with various detection methods in the process of high-pressure torsion. The effect was studied of height to diameter ratio of prepressed molybdenum billets on the microstructure and properties of high-pressure torsion molybdenum billets. The results show that the smaller the height to diameter ratio, the greater the material equivalent shear strain,and the higher the relative density and hardness value of high-pressure torsion molybdenum billets. Furthermore,its internal sub-grain size refinement and microscopic strain accumulation are more obvious. When the height to diameter ratio is reduced from 0.5 to 0.3, the dislocation density caused by grain refinement and strain accumulation increases from 1.67 ×10^14 m 2 to 3.03×10^14 m-2.