采用等径角挤扭工艺制备块体超细晶铝

摘要

采用数值模拟和实验分析方法，对200℃条件下纯铝粉末材料1~4道次A路径等径角挤扭(ECAPT)变形致密行为、晶粒细化机制以及组织和性能演变规律进行研究，制备出组织和性能优良的块体超细晶铝。结果表明：随变形道次的增加，材料内部所累积的应变量不断增大，出现了加工硬化现象，挤压载荷峰值不断上升。ECAPT工艺有效提高了变形材料内部的静水压力，使坯料整体致密程度和变形均匀性得到明显改善。纯铝组织发生了连续动态再结晶，晶粒在不断被细化的同时，其取向差进一步增大，最终在材料内部形成了细小、均匀且被大角度晶界包围的等轴再结晶组织。4道次ECAPT变形后，组织平均晶粒尺寸约为600 nm，抗拉强度达到123.3 MPa。%The deformation and densification behaviors of pure Al powders during 1-4 passes equal channel angular pressing and torsion (ECAPT) under route A at 200 ℃ were investigated using numerical simulation and experiment investigation. In addition, both grain refinement mechanism and the evolution of microstructure and mechanical properties were deeply discussed. The bulk ultrafine­grained pure aluminum with fine microstructure and enhanced mechanical properties was fabricated. The results show that with the increasing pass number of ECAPT, the imposed strain increases. Due to the work hardening, the peak load also increases. As the hydrostatic pressure increases under multi­pass ECAPT, residual porosities in the powder consolidates are effectively shrunk and closed, which contributes to the improvement of deformation uniformity and density of the compacts. During ECAPT process, continuous dynamic recrystallization occurs. As the number of ECAPT passes increases, grains are further refined and mechanical properties are largely enhanced. After 4 passes of ECAPT, the microstructure consists of homogeneous ultrafine grains of 600 nm in size and equiaxed in shape with high angle grain boundaries. Moreover, the tensile strength reaches 123.3 MPa.