等径角挤扭变形过程中纯铝粉末材料的显微组织与力学性能

Microstructure Characteristics and Mechanical Properties on Consolidation of Pure Al Particles through Equal Channel Angular Pressing and Torsion

采用EBSD和TEM研究了200℃下,纯铝粉末材料经不同道次ECAPT变形后的微观组织,并进行了显微硬度和相对密度测试。结果表明,1道次ECAPT变形后,材料显著细化但变形不均匀,晶粒基本沿剪切方向呈条带状分布,平均晶粒尺寸约为5.20μm,但多为小角度晶界结构。随着变形道次的增加,亚晶在不断被细化的同时晶粒间的取向差不断增大,形状更加趋于等轴,该过程可认为发生了连续动态再结晶。4道次变形后,材料内部形成了均匀、细小且呈大角度晶界分布的等轴再结晶组织,最小晶粒尺寸可达0.5μm。ECAPT变形过程中,晶粒细化机制为机械剪切、应变累积和动态再结晶三者的综合作用,粉末材料力学性能的提高与组织致密、细晶强化和位错强化等因素有关。

Equal channel angular pressing and torsion （ECAPT） were used as a technique for consolidating pure Al particles at 200℃. The influence of ECAPT passes number on pore AI compacts was analyzed in terms of microstructure, density and mechanical properties using electron backscattering diffraction （EBSD） , transmission electron microscopy （TEM） , microhardness test and density meas- urement. It was found that microstructures after 1 pass were featured elongated grains of intensively sheared powder particles with low angle boundaries. The materials were further refined along with the increased microhardness and density by increasing the number of ECAPT passes. At the same time, dynamic recovery and dynamic reerystallization were occurred during ECAPT processing. After 4 passes of ECAPT, full density was achieved. The microstructure was consisted of uhrafine grains of 0.5μm in size and equiaxed in shape with mostly high angle boundaries. The grain refinement mechanism was related to intensive shearing, strain accumulation as well as dynamic recrystallization. The improvement in the mechanical properties of the compaction was attributed to microstructure densification and grain refinement.