Microstructures and mechanical properties of modified AZ31-Zr-Sc alloys

Abstract

The effects of minor Zr and Sc on the microstructures and mechanical properties of AZ31 have been determined. It is well known that the ductility of AZ31 is strongly dominated by the grain size of the microstructure. The AZ31-Zr-Sc alloy is a new frontier for development of fine-grain magnesium alloys. This paper investigated the enhancement of the grain refinement and ductility of AZ31-Zr-Sc alloys. A series of deformation processes and tensile tests were performed to observe the change of microstructure and the fracture behavior of this modified alloy. The observations of the microstructure and the cavities in tensile tests at elevated temperature have provided a better understanding of the deformation mechanism of AZ31-Zr-Sc alloy. The results indicate that both Sc and Zr precisely enhanced the grain refinement, and the proper process parameters also enhanced the ductility. The average grain size of the modified alloys was 3.5 mu m after rolling and 2.03 mu m after ECAE. The ductility of modified alloys after equal channel angular extrusion (ECAE) was 324% at 300 degrees C under tensile strain rate of 10(-3) s(-1). Zr particles and fine nano-scale Mn-Sc precipitates were found in the microstructure. Based on the tensile test results, a PDA casing was successfully stamped with AZ31-0.15Zr-0.03Sc at 270 degrees C. (C) 2007 Published by Elsevier B.V.