工业纯铝等通道球形转角膨胀挤压变形的力学与摩擦学性能

Mechanical and Tribological Properties of Commercially Pure Aluminum Processed by Equal Channel Angular Expansion Extrusion with Spherical Cavity

摘要:

对传统等通道转角挤压工艺(Equal Channel Angular Extrusion, ECAE)进行改进,提出一种新型剧烈塑性变形法(severe plastic deformation, SPD)——等通道球形转角膨胀挤压(Equal Channel Angular Expansion Extrusion with Spherical Cavity, ECAEE-SC)。该工艺通过耦合镦-剪-挤等多种变形效应,可在单道次挤压下实现坯料内部较大的塑性应变累积,进而获得理想的晶粒细化与性能提升效果。在室温条件下采用ECAEE-SC工艺对工业纯铝(Al-1060)进行单道次挤压,并与相同条件下的2道次ECAE变形结果进行对比。采用EBSD、SEM等测试手段,研究了工业纯铝ECAEE-SC变形晶粒特征与磨损表面形貌,并测试了变形材料显微硬度、拉伸性能与摩擦学性能。结果表明,在ECAEE-SC工艺剧烈塑性应变诱导下,工业纯铝经单道次挤压变形后晶粒显著细化,呈典型的剪切条带状特征。与初始退火态相比,变形材料显微硬度与抗拉强度分别提升了92.6%和91.8%,且性能提升效果明显优于2道次ECAE变形。同时, ECAEE-SC工艺有效提高了工业纯铝的耐磨性能,工业纯铝变形后表面磨痕宽度最小,磨痕深度最浅,其磨损机理以磨粒磨损为主导。

Abstract:

A novel severe plastic deformation (SPD) method, entitled Equal Channel Angular Expansion Extrusion with Spherical Cavity (ECAEE-SC) was introduced based on a modification of the conventional Equal Channel Angular Extrusion (ECAE) process. By integrating expansion, shear and extrusion deformations in a single extrusion pass, ECAEE-SC process could induce larger accumulated strains into the billet, resulting in the significant grain refinement and the associated properties improvement. In the present study, commercially pure aluminum (Al-1060) was subjected to one pass of ECAEE-SC process at room temperature, and two passes of ECAE process were also conducted for comparison. The microstructure, Vickers hardness, tensile properties and wear properties of processed material were investigated. The results showed that after one pass of ECAEE-SC process, the grains of ECAEE-SC processed aluminum were greatly refined with a typically elongated microstructure due to the high level of strains induced in the material. The hardness and tensile strength of ECAEE-SC processed material were increased with a significantly growth almost 92.6% and 91.8% than the initial material, respectively. These improvements were considerately higher than that achieved by two passes of ECAE process. Moreover, the wear resistance of ECAEE-SC processed material was also enhanced. The worn surface morphology of ECAEE-SC processed sample represented the minimum width and depth of the wear scars, indicating that the wear mechanism could be dominated by abrasive wear.