Compressive deformation of semi-solid SiC_p/ZA27 composites

The semi-solid compressive deformation behaviors of two kinds of SiC_p/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 time. 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. The specimen with uniform deformation and without cracks is obtained after being held at 470°C 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 one. Under the same deformation condition, 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 microstructure under different conditions and the deformation mechanisms at different deformation stages.