新型热处理工艺对搅拌摩擦焊接头性能的影响

摘要

A new post-weld heat treatment process is presented to inhibit the abnormal grain growth (AGG) of friction stir welded (FSW) joints during the post-weld heat treatment and to ensure the strength and toughness of the FSW joints.The 2024-O aluminum alloy FSW joints are heated at 450 ℃ for 40 min then are quenched in water,followed by cold stretching and artificial aging.It is found that no AGG occurs in the joints during the solid-solution treatment at 450 ℃.The hardness and strength of the joints increase as the amount of the cold stretching increases after the solid-solution treatment followed by cold stretching and artificial aging.When the joints have a 10％ cold stretching,the hardness and the ultimate strength reach the maximum value.Therefore,the stability of microstructure and the mechanical of properties the FSW joints can be improved by adopting the new post-weld heat treatment process.%为了抑制焊后热处理过程中搅拌摩擦焊(FSW)接头晶粒异常长大(AGG)现象的发生、保证接头的强韧性,提出固溶-变形-时效一体化的新型焊后热处理工艺.该工艺以2024-O铝合金FSW接头为研究对象,在450℃保温40 min后水淬至室温,然后冷拉伸变形,并于190℃人工时效处理.经光学显微镜观察发现,450℃固溶处理能够显著抑制接头AGG现象的发生.固溶后冷变形结合后续人工时效处理工艺,接头力学性能明显改善,接头显微硬度和强度随着冷变形量的增加而不断提高,当变形量为10％时,接头的硬度和强度值达到最大.由于接头没有发生AGG,焊缝细小的等轴晶和析出相使得新型焊后热处理FSW接头的强度、硬度和塑性均高于传统固溶时效热处理接头.