Nucleation mechanisms of equiaxed grains in the fusion zone of aluminum-lithium alloys by laser welding

Journal of Materials Research and Technology

Gaoyang Mi¹  Yuqiang Li¹  Ping Jiang¹  Shaoning Geng²  Chunming Wang²  Chu Han² 

[1] Technology, 430074, Wuhan, PR China;;The State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science &

关键词: Aluminum-lithium alloys;    Laser welding;    Overlap welding;    Grain detachment;    Heterogeneous nucleation;   

DOI  :  

来源: DOAJ

【 摘 要 】

The formation of different microstructures in aluminum-lithium alloys welding joints by laser welding has not been fully understood at the moment. In this study, the nucleation mechanisms of equiaxed grains in the fusion zone of aluminum-lithium alloys during laser welding are investigated. Two different kinds of equiaxed grains, i.e., non-dendritic equiaxed grains and dendritic equiaxed grains, are discovered. An improved method based on an overlap welding procedure is proposed to clarify the nucleation mechanisms. Two nucleation mechanisms, i.e., grain detachment and heterogeneous nucleation, are simultaneously responsible for the formation of equiaxed grains. The grain detachment, caused by the flow in the molten pool, leads to the formation of non-dendritic equiaxed grains and a part of coarse dendritic equiaxed grains. The direct evidence that the convection of laser welding molten pool causes grains to be detached from the base metal is found for the first time. Most of the dendritic equiaxed grains grow on heterogeneous nucleation particles. D022-Al3Ti and D023-Al3Zr are the main heterogeneous nucleation phases during laser welding.

【 授权许可】

Unknown