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对AZ31B镁合金进行搅拌摩擦焊接,研究热处理前后焊接接头组织及性能的变化。结果表明:焊后热处理可以显著改善焊接接头的力学性能;当搅拌头的旋转速度为600r.min-1,焊接速度为47.5mm.min-1,接头的抗拉强度为168MPa,延伸率为3.6%。热处理后,接头的抗拉强度和延伸率最高可达205MPa和8.6%,比热处理前分别提高22.02%和138.89%;接头的最佳热处理工艺为:退火温度250℃,保温1h;随着退火温度的升高,焊核区晶粒的长大速度大于热影响区/热机影响区混合区域(HAZ/TMAZ)。当退火温度高于250℃时,焊接接头的拉伸断口主要为扁条状韧窝,呈现出微孔聚合韧性断裂特征。
The friction stir welding of AZ31B magnesium alloy was carried out to study the microstructure and properties of welded joints before and after heat treatment. The results show that the post-weld heat treatment can significantly improve the mechanical properties of the welded joint. When the rotating speed of the stirring head is 600r.min-1, the welding speed is 47.5mm.min-1, the tensile strength of the joint is 168MPa and the elongation is 3.6 %. After heat treatment, the tensile strength and elongation of the joint can reach 205MPa and 8.6%, respectively, 22.02% and 138.89% higher than those before heat treatment. The optimal heat treatment process of the joint is as follows: annealing temperature is 250 ℃, holding time is 1h; with the annealing temperature The grain growth rate in the nugget zone is larger than that in the heat affected zone / heat affected zone (HAZ / TMAZ). When the annealing temperature is higher than 250 ℃, the tensile fracture of the welded joints is mainly flat bar dimples, showing the characteristics of microporous polymerized ductile fracture.