球形分流对等通道转角挤压工业纯铝组织性能的影响

Influence of spherical cavity on microstructure and properties of commercially pure aluminum during equal channel angular extrusion process

基于传统等通道转角挤压(Equal Channel Angular Extrusion, ECAE)的变形原理,开发设计出一种具有球形空腔结构的新型复合大塑性变形工艺--等通道球形转角挤压(Equal Channel Angular Extrusion with Spherical Cavity, ECAE-SC)。以ECAE工艺为对比参照,开展了室温条件下工业纯铝单道次ECAE-SC挤压实验研究,进行了金相显微分析、显微硬度测试和球-面接触往复式摩擦磨损试验,获得了变形材料的显微组织、显微硬度、摩擦系数、磨损率和三维磨损形貌等特征参数.研究表明:ECAE-SC球形转角的圆滑过渡可大幅提高模具外角处金属的流动性,有效避免产生传统ECAE单道次变形"死区",挤出试样头部翘曲现象得到显著改善;室温单道次ECAE-SC变形后,工业纯铝晶粒细化明显,显微硬度值由初始36.6HV增加至58.7HV,比同条件下ECAE变形试样(52.8HV)提高了11.2%;ECAE-SC变形材料耐磨性能最好,并表现出良好的摩擦磨损稳定性,磨损机制从磨粒磨损和氧化剥层磨损为主导的混合磨损机制转变为以磨粒磨损为主导的磨损机制。

A new continuous severe plastic deformation(SPD) technique named equal channel angular extrusion with spherical cavity(ECAE-SC) was proposed based on the modification of the conventional equal channel angular extrusion(ECAE) die. ECAE process was used as a comparison. Commercially pure aluminum(Al-1060) was subjected to ECAE-SC for a single pass at room temperature. The influence of spherical cavity on microstructure and properties were evaluated through microstructure analysis, Vickers microhardness(HV) testing, and reciprocating friction-wear test. Vickers microhardness values, friction coefficients, wear rates, and three-dimensional wear morphologies were obtained as well. Results showed that the spherical cavity of ECAE-SC die could greatly improve the metal flow at the outer corner of the die, thus reducing "dead zone" and head bending of 1 P-ECAE processed billet. After one pass of ECAE-SC, the grains were refined, and microhardness was increased from 36.6 HV in the as-cast state to 58.7 HV, which was 11.2% higher than that of ECAE process(52.8 HV). Compared with ECAE, ECAE-SC processed aluminum exhibited better wear resistance and wear stability. The wear mechanism of commercially pure aluminum after ECAE process was dominated by a mixed wear mechanism containing abrasive wear and oxidation wear, while that after ECAE-SC process was a wear mechanism dominated by abrasive wear.