Liquation Cracking Tendency of Novel Al-Mg-Zn Alloys with a Zn/Mg Ratio below 1.0 during Fusion Welding

• Main Authors: Di Zhang, Xin Zhao, Yanlin Pan, Hongxiang Li, Li Zhou, Jishan Zhang, Linzhong Zhuang
• Format: Article
• Language: English
• Published: MDPI AG 2020-02-01
• Series: Metals
• Subjects: welding; liquation cracking susceptibility; al alloy; non-equilibrium solidification
• Online Access: https://www.mdpi.com/2075-4701/10/2/222

The main obstacle for the application of high strength 7××× series aluminum alloys is that these alloys are susceptible to hot cracking during fusion welding. This study presents the liquation cracking susceptibility of the novel T-Mg₃₂(AlZn)₄₉ phase strengthened Al-Mg-Zn alloy with a Zn/Mg ratio below 1.0 by a circular-patch welding test, and compared the liquation cracking tendency with η-MgZn₂ phase strengthened 7××× series alloys whose Zn/Mg ratios are above 1.0. It was found that all these novel Al-Mg-Zn alloys still have as low a liquation cracking susceptibility as traditional 5××× series alloys, surpassing that of traditional 7××× series alloys substantially. It was noticed that the increase of the Zn/Mg ratio will result in a larger difference between the fraction solids of the fusion zone and the partially melted zone during the terminal solidification stage, which can lead to a wider crack healing disparity between these two areas and thus result in different liquation cracking susceptibilities in different alloys.