Effect of Pre- and Post-Weld Heat Treatment on Microstructure and Properties of 2195 Al-Li Alloy Double-Sided Friction Stir Welded Joints
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摘要: 采用双面搅拌摩擦焊方法对6 mm厚2195铝锂合金板进行焊接,对比研究了焊前与焊后热处理(410 ℃×1 h退火+510 ℃×1 h固溶+155℃×1 h人工时效)对接头显微组织及力学性能的影响。结果表明:焊前热处理的接头焊核区晶粒呈细小等轴状,平均晶粒尺寸约为9.2μm,而焊后热处理的焊核区晶粒发生了异常长大现象,平均晶粒尺寸达到0.3 mm。焊前热处理接头的抗拉强度比焊后热处理条件下的接头高约4.7%,断后伸长率也得到明显提高,且焊前热处理接头的拉伸断裂方式为韧性断裂,焊后热处理接头的拉伸断裂方式为脆性断裂。焊前热处理接头的最大弯曲角度大于焊后热处理接头,具有良好的塑性变形能力。Abstract: 6 mm thick 2195 aluminum-lithium alloy plates were connected by double-sided friction stir welding. The effects of pre- and post-weld heat treatment(410 ℃×1 h annealing + 510 ℃×1 h solution and 155 ℃×1 h artificial aging) on the microstructure and mechanical properties of joints were compared and studied. The results show that the grains in the weld nugget area of the joint with pre-weld heat treatment were small and equiaxed, and the average grain size was about 9.2 μm. The grains in the weld nugget area with post-weld heat treatment grew abnormally, and the average grain size reached 0.3 mm. The tensile strength of the joint with pre-weld heat treatment was about 4.7% higher than that with post-weld heat treatment, and the percentage elongation after fracture was improved obviously. The tensile fracture mode of the joint with pre-weld heat treatment was ductile fracture, and that with post-weld heat treatment was brittle fracture. The maximum bending angle of the joint with pre-weld heat treatment was larger than the joint with post-weld heat treatment, indicating the joint had good plastic deformation ability.
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Keywords:
- Al-Li alloy /
- friction stir welding /
- heat treatment /
- microstructure /
- mechanical property
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