Study On Microstructure And Fatigue Behavior Of SiC_p Reinforced Al-Si Matrix Composite

In order to reveal the deformation features of Al-Si alloys and SiC_p/Al-Si composite alloys,the microstructure characteristics,mechanical properties and fracture surface patterns were investigated by using metallographic microscope,scanning electron microscope(SEM),universal testing machine,fatigue machine and so on.It was found that the fracture mode of Al-Si alloys was brittle fracture and the tensile strengths and elongations of these alloys were almost the same according to the tensile experiment from room temperature up to 100?.When the tensile test carrying out between 200? to 350?,the crack propagations of samples were caused by the dimples formed by micro-pore aggregations,meaning the ductile fracture happened.The elongation of SiC_p/Al-Si composite alloys would be increased with the temperature of tensile test.Meanwhile,the tensile strengths of these samples would be decreased.In comparison with Al-Si alloys,the SiC_p/Al-Si alloys own higher mechanical properties.The softening phenomenon of SiC_p/Al-Si alloys would be happened slightly and the elongation of sample increased obviously with the increase of temperature.At the same temperature,the elongation of Al-Si alloys was larger than that of SiC_p/Al-Si alloys,which might be attributed to the decrease of ductile formed by addition of SiC particles.Furthermore,the reduction degree of elongation of these samples was positively proportional to the volume fraction of SiC particles in the system.It was observed that the level of low cycle fatigue cycle of Al-Si alloys decreased obviously with the increase of temperature.At room temperature,the cyclic hardening phenomenon of samples was observed.While,the slight cyclic softening of samples was appeared at 200?and 350 0C.The fatigue life of Al-Si alloys would decrease with the increase of temperature.At 350?,the specimen exhibited short low cycle fatigue life,which was over an order of magnitude as compared with the specimen at room temperature.In comparison with specimens containing 3 vol.% and5 vol.% SiC particles,the cyclic stress level of 8 vol.% SiC_p/Al-Si alloy was higher and more stable,meaning this composite alloy obtain optimum fatigue performance.Inaddition,the test temperature has a noticeable influence on the fatigue life of composite alloys.With the relative low level of fatigue performance,it can be found thatthe fatigue life of SiC_p/Al-Si composite alloy was inversely proportional to the test temperature.