Hot Cracking and Microstructure of Welding Joint of Magnesium Alloy AZ91D

Abstract:

The microstructure and cracking characteristics of MIG welded magnesium alloy (AZ91D) joint, and the effect of welding speed on cracking susceptibility have been investigated. The result indicates the welded joint consists of primary α-Mg and divorced phases (eutectic α-Mg + eutectic β-Mg₁₇Al₁₂), the latter mainly distributing along the α-Mg grain boundaries. The weld of the magnesium alloy displays a high cracking susceptibility. The cracks are mainly formed in the arc crater at the end of the weld. These cracks propagate along the α-Mg grain boundary, and they belong to the solidification cracking. These solidification cracks are resulted by the joint function of the low melting point liquid film in the weld and the tensile stress suffered by the weld metal during the solidification process. The low melting point liquid film is the internal cause to form the solidification cracks, while the tensile stress is a necessary condition. Limiting the amount of the low melting point eutectic and decreasing the tensile stress of the welding joint are two effective methods to improve the solidification cracking susceptibility of the magnesium alloy weld.

• Periodical: Advanced Materials Research (Volumes 753-755)
• Pages: 435-438
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.753-755.435
• Online since: August 2013
• Authors: De Xin Sun, De Li Cui, Jiang Tian Shi
• Keywords: Liquation Cracking, Magnesium Alloy AZ91D, MIG Arc Welding, Solidification Cracking

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