HPT不同压力下纯钼的组织和性能及热稳定性

Microstructure, Performance and Thermal Stability of Pure Molybdenum by HPT Method Under Different Pressure

通过高压扭转实验,在350℃条件下将纯钼粉末制备成相对密度达98%以上的金属钼坯,利用多种检测手段分析了高压扭转过程中钼粉颗粒孔隙演变及致密强化规律。通过改变预压钼坯压力参数,探讨了压力对压扭钼坯微观结构和力学性能及其热稳定性的影响。结果表明:压力由2.0 GPa增大到3.0 GPa,压扭钼坯致密度提升显著,其内部亚晶细化,微观应变增加,试样整体显微硬度值随压力增大而升高,边缘处略有降低。随压力增大,差热分析(DSC)后组织未发生显著长大,热稳定性较好。

The pure molybdenum powder was consolidated to bulk materials with a relative density over 98% via the high-pressure torsion(HPT) processing at 350 oC. The deformation of particles and pores, the evolution of crystallite size and dislocation density, and the strengthening mechanism during HPT processing were analyzed through scanning electron microscopy(SEM), X-ray diffraction(XRD)and the Vickers microhardness. The influence of applied pressure on the microstructure evolution, mechanical properties and thermal stability during HPT were discussed. The results show that the relative density and average microhardness of the HPT processed sample improve obviously with the increasing applied pressure from 2.0 GPa to 3.0 GPa. Also, the crystallite size and microstrain experience a decrease and an increase with the increasing applied pressure, respectively, which leads to the increase in dislocation density. In addition, the grain size in the HPT processed sample has a finite increase during the DSC processing, which indicates the thermal stability of the HPT processed microstructure.