Effect of ultrafine SiC particles on microstructure and property of milled nanocrystalline AZ91 magnesium alloys

The SiC particle (SiC_p) reinforced magnesium matrix composite powders (AZ91‒xSiC_p, x=5%, 10%, 15%, volume fraction) were synthesized by mechanical milling. After the mechanical milling, the grain size of the magnesium matrix was refined to nanoscale, and the ultrafine SiC particles were dispersed into the magnesium matrix uniformly. The effect of SiC_p on the microstructure of the milled nanocrystalline AZ91 magnesium alloys was analyzed. In the results, SiC_p could accelerate the refining of magnesium matrix. Meanwhile, both the dissolving of Al element into the magnesium matrix and the refining of SiC_p are inhibited due to the increasing of SiC_p. The hardness of AZ91‒xSiC_p composites (x=5%, 10%, 15%) is HV 166, HV 175, and HV 185, respectively. The contribution ratio of grain boundary strengthening, Orowan strengthening, solid solution strengthening, and load-bearing strengthening to the milled AZ91‒xSiC_p composites is about 86.9%, 7.4%, 1.8% and 3.8%, respectively.