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搅拌摩擦修复是一种较新的裂纹修复技术,针对含预制0.8 mm深长直裂纹的2A12航空铝合金进行搅拌摩擦修复试验。修复后利用光学显微镜和显微硬度仪对其表面、截面微观组织和显微硬度进行了研究。结果发现:修复区显微硬度分布基本呈“W”形,表面与截面0.5 mm处硬度曲线基本一致,前进侧硬度低于返回侧,且硬度最低值出现在热影响区。截面修复区硬度分布为上部高于下部,且沿中心不对称分布。随厚度的增加,轴肩产生的摩擦热自上到下不断降低,是造成中下部修复性能降低的主要原因。修复区性能下降的主要原因是在修复和冷却过程中S相和θ相的固溶、不完全析出或分布不均匀,加上晶粒内部位错强化效果的降低,使得修复后硬度整体低于母材。
Friction stirreaction repair is a newer technique of crack repair, which is aimed at the friction stir test of 2A12 aviation aluminum alloy with prefabricated 0.8 mm deep and long straight crack. After repair, the surface, cross-section microstructure and microhardness were studied by optical microscope and microhardness tester. The results show that the distribution of microhardness in the rehabilitated zone is basically “W” shape, the hardness curve of the surface is basically the same as that of the 0.5 mm cross section, the hardness of the forward side is lower than the return side, and the lowest hardness appears in the heat affected zone. The hardness distribution of the section repair area is higher than the lower part in the upper part and asymmetrically distributed along the center. With the increase of the thickness, the frictional heat produced by the shoulders continuously decreases from top to bottom, which is the main reason for the lower repair performance in the middle and lower parts. The main reason for the decrease in the performance of the repaired zone is the solid solution of the S phase and the θ phase in the process of repairing and cooling, incomplete precipitation or uneven distribution, and the decrease of dislocation strengthening effect inside the crystal grain so that the overall hardness after repairing is lower than Base metal.