Effect of Solution Treatment on Microstructure Evolution and Mechanical Properties of Mg-6.0Zn-0.6Y-0.5Zr Alloy Processed by Equal Channel Angular Extrusion

Abstract

The effect of solution treatment before equal channel angular extrusion (ECAE) on the evolution of microstructures and mechanical properties in as-cast Mg-6.0Zn-0.6Y-0.5Zr alloy after different ECAE passes has been systematically investigated. The micrographs and tensile results showed that the solution treatment significantly influenced the microstructural evolution, as well as tensile strength and elongation. ECAE processing results in producing finer grain structure both in the as-cast and as-solutionized alloys when the passes increased. However, solution treatment before ECAE provides a significant increase in forming rate of fine recrystallized grains during ECAE at high temperature of 623 K. A fully recrystallized microstructure was observed after 8 passes in the as-solutionized alloy, while it was not finished even after 8 passes in the as-cast alloy. The ductility of as-solutionized alloy is always significantly better than those of the as-cast alloy. However, the strengths of the former are better than those of the later only after the passes beyond 6 passes.

Mechanistic origin and prediction of enhanced ductility in magnesium alloys

“…For Mg-Zn-X-X′ alloys, high Zn concentrations raise the cross-slip barrier considerably, leading to c < 0, which is unfavorable for ductility. This is consistent with broad experimental trends where ductility generally decreases or saturates with increasing Zn (19,(28)(29)(30)(31)(32) (fig. S1).…”