铝合金搅拌摩擦焊接头的疲劳性能
首发时间:2011-03-14
摘要:通过疲劳试验对LY12CZ(2A12-T4)、LD10CS(2A14-T6)、5A06-H112、7075-T6和LC4CS搅拌摩擦焊接头的疲劳性能进行了研究,采用光学显微镜和扫描电镜观察焊缝根部组织和疲劳断口形貌,讨论了根部焊接缺陷对疲劳性能的影响。结果表明:5A06-H112搅拌摩擦焊接头疲劳强度(50%存活率)是MIG焊接接头的1.64倍、LY12CZ、7075-T6及LC4CS搅拌摩擦焊接头疲劳强度(50%存活率)与母材比较分别为75%、89.5%和95%。当焊缝根部存在约为0.31~0.46 mm的“弱连接”缺陷时,对搅拌摩擦焊接头疲劳性能产生明显影响。搅拌摩擦焊接过程中搅拌工具的搅拌头顶端与支撑底板间隙控制不合适是产生“弱连接”缺陷的关键因素。
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Fatigue properties of friction stir welds for aluminum alloys
Abstract:The fatigue properties of friction stir welded (FSW) 5A06-H112, LY12CZ, 7075-T6 and LC4CS aluminum alloys were investigated based on the fatigue S-N curve experiments. The microstructure and fatigue fracture surface of friction stir welds were examined by using optical microscopy and scan electrical microscope (SEM) and the effects of root defects on the fatigue properties of FSW joints were discussed. It was found that the fatigue strength (50% of survival probability) of friction stir welds in 5A06-H112 alloys was 1.65 times that of MIG welded joints, and the fatigue strength (50% of survival probability) of LY12CZ, 7075-T6 and LC4CS alloys were 75%, 89.5% and 95% that of base materials respectively. Weak-bonding defects with sizes of 0.31-0.46 mm existed at the root site had obvious influence on the fatigue properties of friction stir welds. The inappropriate gap controlling between the pin tip and the supported platform surface should be the key factor to produce the weak-bonding defects.
Keywords: friction stir welding aluminum alloys joints mechanical properties microstructure
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