SiCp/Al复合材料超精密车削仿真与试验研究

Simulation and Experimental Research on Ultra-precision Turning of SiCp/Al Composites

摘要:

针对SiC_p/Al复合材料因脆性相SiC的加入而导致难以形出高质量加工表面等问题,本文采用分子动力学模拟和超精密车削试验的方法对SiC_p/Al复合材料纳米尺度材料去除过程进行研究,重点分析了单晶金刚石超精密切削SiC_p/Al复合材料中的加工表面形成机理、脆塑性转变以及刀具磨损机理。结果表明：高压相变是引起SiC_p/Al复合材料中SiC脆性材料的脆塑性转变的主要原因。随着切削深度的递增,SiC_p/Al复合材料中SiC颗粒加工方式由延性去除,到脆塑性混合方式去除,最后演变为纯脆性方式。SiC_p/Al复合材料中SiC-Al界面和Al基体存在,影响了SiC_p/Al复合材料中SiC颗粒去除的脆塑性转变机制。待加工表面上拉应力的存在会诱导微裂纹尖峰,是切削区域脆性SiC材料裂纹萌生的直接诱因。单晶金刚石刀具主要磨损机理为硬质SiC颗粒的磨粒磨损和切削诱导的石墨化。

Abstract:

Aimed at the difficulty in producing high-quality machined surface due to the existence of brittle-phase SiC in SiC_p/Al composites, this paper used the molecular dynamics simulation and ultra-precision turning test to investigate the material removal process of SiC_p/Al composites at nanoscale, and focused on the machined surface formation mechanism, brittle-ductile transition and tool wear mechanism in single crystal diamond ultra-precision turning of SiC_p/Al composites. The results indicate that high-pressure phase transition is the main reason for the brittle-ductile transition of brittle-phase SiC in SiC_p/Al composites. With the increase of cutting depth, the removal of SiC particles in SiC_p/Al composites experienced from ductile cutting mode to hybrid brittle-ductile cutting mode and finally to purely brittle cutting mode. The SiC-Al interface and soft Al matrix in SiCp/Al composites considerably affected the brittle-ductile cutting mode transition mechanism when machining SiC particles in SiC_p/Al composites. The existence of tensile stress on the uncut chip could induce the peak of brittle SiC crack initiation in the cutting zone. The primary wear mechanisms of SCD tools were abrasive wear originated from hard SiC particles’ scrape and machining induced graphitization.