Microstructure And Properties Of Nano-SiCp/AZ91 Magnesium Matrix Composite Processed By Equal Channel Angular Pressing

Equal channel angular pressing (ECAP) was applied to the as-extruded and as-casted 1vol.% nano-SiCp/AZ91 composite fabricated by stirring casting, respectively. The optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to investigate the microstructure of the SiCp/AZ91 composites. Texture development of the as-extruded and ECAPed SiCp/AZ91 composites was investigated by neutron diffractometer. The mechanical properties were tested by tensile and compression test at room temperature. The damping capacities were measured by dynamic mechanical analyzer (DMA) of Q-800 type.The research showed that the grains were significantly refined because of recrystallization when ECAP was performed on SiCp/AZ91 composites. The results showed that some grain sizes of as-casted composites have been reduced to about 500nm by 2 passes of ECAP at 400℃, some grain size of as-extruded composites have been reduced to almost 450nm by 3 passes of ECAP at 250℃.When the composites were ECAPed by 1 pass at 250℃,300℃and 350℃, basal planes have rotated and the main texture compoent has been changed, the yield and the ultimate tensile strength of the composites increased greatly. With the increasing of pressing temperature, the yield strength of composites decreased for that the texture was weaken. With the increasing of pressing passes at each temperature, the yield and ultimate tensile strengths decrease because of the weakening of texture.The investigation of the strain amplitude dependent damping capacity indicated that the curve showed strain amplitude dependent and independent regions. The curves were well interpreted by G-L dislocation model. The investigation of the temperature dependent damping capacity showed the damping capacity decreased when the temperature increased. The curves of the temperature dependent damping capacity of the ECAPed SiCp/AZ91 composites exhibit two typical peaks, which were found between 100℃and 150℃, around 325℃, respectively. The reasons for the peaks are that the first peak was induced by the slipping of dislocation along basal planes while the second by recrystallization.