SiC_p/Al复合材料的超精密车削试验

Experiments of ultra-precision turning of SiC_p/Al composites

试验研究了碳化硅颗粒增强铝基复合材料(SiCp/Al)的超精密车削加工性能。使用扫描电镜(SEM)对已加工表面、切屑及其根部、刀具前/后刀面磨损带进行观察,使用表面粗糙度轮廓仪对各种切削条件下的加工表面粗糙度轮廓进行测试分析。结果表明,该材料的加工表面常残留微孔洞、微裂纹、坑洞、划痕、残留物突起及基体材料撕裂等微观缺陷,刀具几何参数、切削速度、进给量、增强颗粒尺寸和材料体积分数是影响表面粗糙度的主要因素。由于切削变形区微裂纹动态形成的作用,超精密切削该材料时一般形成锯齿型切屑。刀具-工件的相对振动、基体撕裂增强颗粒拔出、破碎、压入等是该材料超精密车削表面形成的主要机制。单晶金刚石(SCD)刀具主要发生微磨损、崩刃、剥落和磨粒磨损,聚晶金刚石(PCD)刀具主要发生磨粒磨损和粘结磨损。结论表明SiCp/Al的超精密切削加工性较差,但通过选择合适的工艺参数,体积分数为15%的SiCp/2024Al加工表面粗糙度Ra可达24.7nm。

The ultra-precision machinability of SiCp/Al composites is investigated experimentally. A scanning electron microscope （SEM） is used to examine the machined surfaces, chips, chip roots and tool wear lands, and a surface profiling instrument is taken to measure the surface profile roughnesses in different turning conditions. The results show that the machined surface remains a lot of defects such as pits, voids, microcracks, grooves, protuberances, matrix tearing, etc. The tool geometries, cutting speeds, feed rates, particle reinforcement sizes and the volume fractions are the significant influence factors of surface roughness. Generally, a segmental chip is formed in turning composites due to the effect of dynamic microcrack behavior. The tool-workpiece relative vibration and the removal modes of SiC particles are the main mechanisms of surface generation. The microwear, chipping, peeling and the abrasive wear are the main wear patterns by using the Single Crystal Diamond （SCD） tool, while Polycrystalline Diamond （PCD） tool mainly suffers from the abrasive wear on the rake face and the adhesive wear on the flank face. The experimental result indicates that the SiCp/Al composites has a relatively bad machinability. However, when the cutting parameters are rationally chosen, a surface roughness Ra of 24.7 nm can be obtained for SiCp/2024Al（in a volume fraction of 15%）.