Abstract: Wear model and characteristics of the second cutting deformation zone,that is,between the rake face of cutter and chips were investigated by carrying out diamond PCD cutter ultraprecision machining test of SiC noncontinuous reinforced aluminum composites,and measuring analysis with atom force microscope(AFM) and scan electronic microscope(SEM).Chip-roots were obtained with the device of quick dropping tool,and effects of wedgy Built-up Edge(BUE) were analyzed.Micro-morphologies of worn PCD cutter edge were observed with AFM,and wear mechanism was analyzed.Results show that very small BUE is still produced on the rake face of cutter in the process of ultraprecision turning of the SiC noncontinuous reinforced aluminum composites.The wear resistance of SiC aluminum composites is clearly better than that of aluminum matrix,tribological performance of the composite is optimized when adding 20%~25% volume fraction SiC reinforcement.In addition,in the process of ultraprecision machining of aluminum composites,diamond cutting tools are the best candidate.