Effects of multi-pass FSP on the β phase (Mg17Al12) distribution and mechanical properties of AZ91C magnesium alloy

Abstract

Purpose: The principle and advantages of friction stir processing (FSP) for the production of a highly formable Mg alloy, and some convincing experimental results are reported in this paper. The aim is to understand the relationship between the microstructure characteristics and the mechanical properties behaviour of the number of FSP passes AZ91C alloy. Design/methodology/approach: FSP is a solid state processing technique which involves plunging and traversing a square pin profiles FSP tool through the material. In this study, a fine-grained multi-phase AZ91C magnesium alloy was produced by applying FSP on as-cast AZ91C alloy. Findings: FSP achieved grain refinement and homogenization of the as-cast microstructure in Mg alloy AZ91C. FSP produced a fine homogeneous microstructure having a grain size of 6 μm throughout the plate. Also tensile properties of the specimen produced in one, two and three passes were investigated by standard tensile test. Results show that FSP improved the tensile characteristics of the as cast AZ91C alloy significantly. As the number of passes increased, higher UTS and TE were achieved due to finer grains and more dissolution of β phase (Mg17Al12). Originality/value: The present study shows that FSP is an efficient production method for a large-scale plate of a highly formable Mg alloy.