The microstructures and mechanical properties of ultrafine-grained Mg–Zn–Zr alloys fabricated by powder metallurgy

Abstract

Ultrafine-grained Mg-Zn-Zr alloys were fabricated via powder metallurgy. The effect of extrusion temperatures on the microstructures and properties of as-extruded Mg-Zn-Zr alloys was investigated. The results indicated that a trace of MgO phase nanoparticles was produced in the process of mechanical milling, and the fine MgZn2 phases precipitated during hot press sintering and extrusion. As extrusion temperatures increased from 523 K to 623 K, the full dynamic recrystallization (DRX) replaced the partial dynamic recrystallization, and the average grain size increased from 426 nm to 760 nm. Nano-MgO particles and MgZn2 phases were uniformly distributed in the Mg matrix, which enhanced the compressive properties of the extruded alloys. The alloys extruded at 523 K had ultrafine grains with an average size of 426 nm. The compressive yield strength, ultimate compressive strength, and elongation were 324 MPa, 508 MPa, and 15.8%, respectively. The improved strength of the alloy was mainly attributed to the grain refinement and dispersion strengthening of nano-MgO particles and MgZn2 particles.