Friction stir processing to improve grain refinement and superplasticity of Al-Mg-Mn-Cr alloy

Abstract

In this study the Al-4.8Mg-1.0Mn-0.15Cr alloy was frictionally stir processed in order to enhance grain refinement effect and superplastic properties. The microstructure after friction stir processing (FSP) was analyzed using light, scanning and transmission electron microscopies. An additional cold rolling (50%) was performed after the FSP, and a comparative study in terms of microstructure and superplasticity was done between the samples processed using hot rolling and further FSP, FSP and cold rolling, and cold rolling without FSP. The superplastic properties were studied at temperatures of 450 and 500 °C with constant strain rates of 1×10-2 and 1×10-2 s-1. The treatment regime including FSP and further cold rolling improved superplasticity due to fine-grained and homogeneous grain structure with a good thermal stability. At a temperature of 500°C and strain rates of 1×10-3-1×10-2 s-1 the alloy demonstrated 330-450 % elongation with a flow stress of 10-20 MPa.