Fabrication and characterization of magnesium matrix composite processed by combination of friction stir processing and high-energy ball milling

Magnesium matrix composites have been prepared on pure magnesium and AZ31 alloy matrix by a combination of friction stir processing (FSP) and high-energy ball milling (HEBM) techniques. Microstructures and mechanical properties of as-fabricated samples are systematically investigated. The research shows that reinforcement HEBM particles disperse in the stir zone (SZ) as agglomerated streamline clusters and separated particles. In addition, the nano particles less than 100 nm can be directly observed in the SZ. The HEBM particles effectively refined the grains in SZ and probably resulted in high-density dislocations by pinning effect. The results observed by electron back-scattering diffraction (EBSD) also reveal that HEBM particles addition brings positive effect on the grain orientation randomization in the SZ. As for mechanical properties, macrohardness of powder aggregation in pure magnesium matrix is more than twice the value of neighboring normal SZ. In AZ31 alloy matrix composites, HEBM powders addition increased both yield strength and ultimate tensile strength of SZ samples by more than 30% while maintaining high ductility.