对14 mm厚板铝合金搅拌摩擦焊(FSW)接头焊核区微观组织、整体和分层切片力学性能进行了研究。结果表明, 当旋转速度为400 r/min, 焊接速度为60-100 mm/min时, 接头抗拉强度σ b、屈服强度σ0.2和延伸率δ随焊速的升高而降低。焊缝分层切片的σ b, σ 0.2和δ上部最高, 分别达到了186.7 MPa, 100.3 MPa和14.1%;下部最低, 分别为157.5 MPa, 80.2 MPa和10.1%。微观断口中存在大量的网状韧窝, 切片上部韧窝最深, 焊缝根部可见沿晶界的二次裂纹和浅韧窝。显微硬度分布为焊缝上部高于下部, 沿焊缝中心呈不对称分布. 焊核区上部等轴再结晶晶粒尺寸大于焊缝下部. 焊核区上部的第二相粒子相对下部更均匀和细小, 强化作用增强.
Microstructure of weld nugget zone and mechanical properties of the whole and slice in the thick plate joints obtained by friction stir welding (FSW) were studied. The results show that the tensile strength σb, yield strength σ0.2 and elongation δ decrease with increasing weld speed when the rotary speed is constant. The maximum σb, σ0.2 and δ lie in the top weld and reach 186.7MPa, 100.3MPa and 14.1% respectively, while the minimum σb, σ0.2 and δ in the bottom joint only attain 157.5MPa, 80.2MPa and 10.1% separately. The fracture morphologies show that there are lots of meshy dimple and the deepest locates in the top joint. The secondary intercrystalline crack and quasi-cleavage face lie in the root of weld. The microhardness at the top is higher than that at the bottom and presents asymmetrically through the weld centerline. The fine and equiaxial grain size is bigger at the top than that at the bottom and clings together at the root of weld. Compared with the bottom, second-phase particle at the top redissolves into the matrix abundantly and the strengthening effect boosts up.
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