Abstract:The semi-solid compressive deformation behaviors of two kinds of SiCp/ZA27 composites, one was modified by Zr and the other was not modified, were investigated. The results indicate that with increasing strain, the stress of the modified composite first increases to a peak value, then dramatically decreases to a plateau value, and again increases at the final stage of deformation; but for the unmodified composite, after being up to a peak value, the stress decreases slowly at all times. As the deformation temperature or the heating time decreases, or the strain rate increases, the stress level(the peak and the plateau values) and the degree of cracking of the modified specimens all increase, and the specimen with uniform deformation and without cracks is obtained after being held at 470℃ for 30min and deformed at the strain rate of 9.33×10^-3s^-1. But the degree of cracking of the unmodified is just inverse to that of the modified. Under the same deformation conditions, the stress level and the degree of cracking of the unmodified composite are higher than those of the modified one, and the degree of cracking is very serious under any conditions. These phenomena were mainly discussed through analyzing the microstructures under different conditions and deformation mechanisms occurred at different deformation stages.

Key words: SiC_p/ZA27 composite; semi-solid; compressive deformation; microstructure; thixoforming