The Influence of Aluminum Content of AZ61 and AZ80 Magnesium Alloys on Hot Cracking

Abstract

This study aims to investigate how aluminum content in magnesium alloys AZ61 and AZ80 impacts the hot cracking susceptibility of magnesium alloys. Differences in aluminum content are known to influence the total crack length of hot cracking. Magnesium alloy AZ61's total crack length was the longest in one thermal cycle, while AZ80's total crack length increased as the number of thermal cycles increased. The most significant difference between AZ61 and AZ80 was the hot crack at the heat-affected zone (HAZ). As the number of heat inputs increased, the grain would coarsen in the HAZ and precipitation started, which resulted in the accumulation of hot cracks at weld metal HAZ (W. M. HAZ). During the solidification of AZ80, which has higher aluminum content, the segregation of aluminum at the grain boundary caused Mg17Al12 to liquefy, increasing the length of hot cracks. Augmented strain caused miniature cracks between Mg17Al12 and grains. Therefore, aluminum content and augmented strain were found causes of hot cracking susceptibility in magnesium alloys.