The Microstructures and Mechanical Properties of Al-5Mg-1.4Mn Alloy Cast under Near-Rapid Cooling

A high Mn content alloy (Al-5Mg-1.4Mn) has been cast under the condition of near-rapid cooling. The microstructures and mechanical properties of the alloy have been evaluated. The results indicated that under the condition of near-rapid cooling, the as-cast microstructures of the alloy consisted of α-Al matrix plus two types of intermetallics: Al6(Fe,Mn) and Mg2Si. The intermetallics were small and uniformly distributed. During hot and cold rolling, they broke into particles. The particle structures were dense, but small. Some cavities were observed among the Al6(Fe,Mn) fragments. Both the hot band and cold rolled sheet demonstrated excellent mechanical properties. The significant improvements were achieved by increasing Mn to a higher level, while being cast under the condition of near-rapid cooling.