7075铝合金熔覆层的搅拌摩擦加工研究-中国材料进展

文章信息/Info

Title:: Friction Stir Processing on Fusion Welding Area of 7075 Aluminum Alloy

Author(s):: ZHANG Yunlong; LI Ruolin; ZHU Bin; CHENG Liang; （School of Materials Engineering, Jiangsu University of Technology, Changzhou 213001, China）

Keywords:: 7075; aluminum alloy; TIG welding; friction stir processing; mechanical properties

摘要:: 7系超硬铝合金广泛应用于航空航天以及汽车等领域，钨极惰性气体保护（tungsten inert-gas，TIG）电弧焊可用于构件的修复，但熔焊缺陷以及专用丝材的缺乏使得熔覆层的强度不足。采用ER5356铝合金焊丝对7075-T6合金进行熔覆修补，并对TIG熔覆层进行搅拌摩擦加工（friction stir processing, FSP），以期改进熔覆层力学性能。固定TIG焊工艺参数和搅拌头行进速度，研究了搅拌头转速对熔覆层组织、力学性能以及断裂行为的影响，结果表明：TIG熔覆区由粗大的树枝晶组成，FSP消除了熔覆区的宏观缺陷，显著细化晶粒并减小了搅拌区与母材的成分差异。TIG熔覆试样拉伸断口位于硬度和强度最低的熔覆区中心。FSP显著提高了熔覆层的硬度和强度，拉伸断口位于前进侧的热机械影响区。随转速增大，搅拌区平均晶粒尺寸降低，热机械影响区和搅拌区的强度提高而塑性降低。

Abstract:: 7 series duralumin alloys are widely used in aerospace and automotive fields. Tungsten inert gas (TIG) welding can be used to repair components, but the welding defects and the lack of special wire make the strength of the welding layer insufficient. In this paper, ER5356 welding wire was used to 7075-T6 alloy fusion welding, and friction stir processing (FSP) was carried out on TIG welding layer to improve the performance. The effect of rotation speed on the microstructure, mechanical properties and fracture behaviors of the welding layer was studied, with the certain TIG welding processing parameters and traveling speed. The results show that the TIG welding zone (WZ) is composed of coarse dendrites, and FSP eliminates the macroscopic defects in the WZ, significantly refines the grain size and reduces the composition difference between the stirring zone (SZ) and the base metal. The tensile fracture of TIG overlaying sample is located in the center of WZ, which has the lowest hardness and strength. FSP significantly improves the hardness and strength of the welding layer, with the fracture located in the thermo-mechanically affected zone (TMAZ) on the FSP advancing side. With the increase of rotation speed, the average grain size of SZ decreases, the strength of TMAZ and SZ increases, while the plasticity decreases.