航天铝基复合材料零部件超精密加工技术研究

针对航天高碳化硅铝基复合材料零部件采用聚晶金刚石PCD刀具进行了超精密车削加工试验，用原子力显微镜AFM和扫描电子显微镜对其进行了检测，分析了零部件表面粗糙度值的大小及影响因素、SiCw变形破坏机理、已加工表面微观结构及加工变质层特性。结果表明，超精密车削高碳化硅铝基复合材料零部件可以获得超精密级加工表面（如Ra11．5nm）；超精密车削过程中SiC，存在着三种主要变形破坏机理：直接剪断型、拔出型和压入型，且以直接剪断型为主。直接剪断的SiCw对表面粗糙度值影响最小，而后二者是影响表面粗糙度值达到超精密级的主要障碍；超精密加工零部件表面仍会产生很薄的加工变质层。

Study on the Ultraprecision Machining Technology of Aluminum-Matrix Composite Astronautic Parts

The Ultraprecision machining experiments of aluminum-matrix composite astronautic parts with polycrystalloid diamond PCD cutter were done,measurement analysis of surface quality with Atom Force Microscope(AFM) and Scan Electronic Microscope(SEM) was carried,and the roughness value and impact factors and the deformation cut off mechanism of SiC_w and the microstructure of machined surface and subsurface quality were reviewed.The results show that the surface finish of ultraprecision machining grade,that is R_a11.5nm,can be gotten when machining aluminum-matrix composite parts reinforced with SiC_w,but it is hard.The deformation cut off mechanism of SiC_w whiskers in the machining process is that direct cut off,pulling out,putting in,and direct cut off is main deformation mode.The pulling out and putting in mode affect highly for the roughness of ultraprecision machining surface.There is a thin degenerative layer in subsurface,and the higher hardness(HV) location is not at surface.The main reasons of increasing microhardness are the falling to pieces of SiC_w and rearranging of SiC_w.