Microstructure and Mechanical Properties of Laser Welding Joints of 7075 Aluminum Alloy with Filler Wire
YANG Zhihua1, YANG Shanglei1,2, JIANG Yishuai1, WANG Yan1
1 School of Materials Engineering,Shanghai University of Engineering Science, Shanghai 201620; 2 Shanghai Research & Development Center for Key Technologies of Ultra-Intense Laser Processing, Shanghai 201620
Abstract: 7075 aluminum alloy with the thickness of 4 mm was welded with filler wire by the fiber laser equipment. The microstructure, phase structure, fracture morphology and mechanical properties of welding joints were observed and analyzed.The results showed that the edge of the fusion zone (FZ) was mainly columnar dendrite grains,and the center of FZ was mainly equiaxial grains.The microstructure in the heated-affected zone (HAZ) was fibrous along the rolling direction, and the grains in the HAZ were slightly coarsened compared with those in base metal (BM). The phase of BM was mainly composed of α-Al solid solution, the precipitation of S-Al2CuMg and η-MgZn2, but no precipitation was found in FZ.The microhardness value of FZ is the lowest in the welding joint, and a step increase of the microhardness occurred in HAZ.All of the tensile samples which were welded at welding speed from 2 m/min to 4 m/min fractured at FZ, among which the highest tensile strength was 67.5% of BM.The necking phenomenon occurred at the welding joint of all the tensile samples, and the fracture surface was mainly composed of the equiaxed dimples, which is the typical characteristic of ductile fracture.
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2017, Vol. 31 
