Enhancement of strength and ductility of SiCp/AZ91 composites by RD-ECAP processing

In this research, as-cast SICp/AZ91 composites were pre-homogenized at 420 degrees C for 20 h and then processed by rotary-die equal channel angular pressing (RD-ECAP) at 250 degrees C for three different passes (4P, 8P, 16P). The effects of ECAP on the microstructure and mechanical properties were investigated. Results showed that SIC particles were more uniformly distributed, matrix grains were significantly refined, beta-Al12Mg17 phases were precipitated and homogenized, and texture was reformed to preferred crystal orientation after ECAP processing. The mechanical tensile tests showed an effective increase in mechanical properties after ECAP process. After 4P, 8P, 16P ECAP, the strength of the composites increased to 306 MPa, 288 MPa and 285 MPa, respectively; and the ductility increased to 6.4%, 7.3% and 8.2%, respectively. The strength of the composite was slightly decreased and the elongation was gradually increased with the pass number increasing from 4-16P. The enhanced mechanical properties of the composites in this study were ascribed to a combined effect of grain refinement, second phase precipitation, dislocations and texture reforming.