Enhanced mechanical properties in friction stir welded low alloy steel joints via structure refining
Enhanced mechanical properties in friction stir welded low alloy steel joints via structure refining
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DOI：
10.1016/j.msea.2014.03.058
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发表时间：
2014-06
期刊：
影响因子：
6.4
通讯作者：
P. Xue;Y. Komizo;R. Ueji;H. Fujii
中科院分区：
文献类型：
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作者：
P. Xue;Y. Komizo;R. Ueji;H. Fujii
高强度低合金钢的埋弧焊金属分别在 400 rpm (FSW-a) 的较高转速和 125 rpm (FSW-b) 的较低转速下进行搅拌摩擦焊 (FSW)。研究了FSW接头焊缝金属中粗大贝氏体相、细化贝氏体相以及熔核区（NZs）中铁素体相三种典型相组织的显微组织和力学性能。与焊缝金属相比，两个 FSW 接头的 NZ 都实现了增强的机械性能。焊缝金属粗晶粒中明显存在大裂纹沿贝氏体板条扩展，导致脆性准解理断裂。然而，FSW-a接头NZ处的细化贝氏体相结构抑制了大的裂纹扩展，并通过韧窝断裂实现了强度和韧性的增强。同时，由于延性铁素体组织的细化，FSW-b 接头的 NZ 部分获得了增强的机械性能，包括强度和延展性以及韧性。
Submerged arc weld metal of a high strength low alloy steel was subjected to friction stir welding (FSW) at a higher rotation rate of 400 rpm (FSW-a) and a lower rotation rate of 125 rpm (FSW-b), respectively. The microstructures and mechanical properties of three typical phase structures, coarse bainite phase in the weld metal, refined bainite phase and ferrite phase in the nugget zones (NZs) of FSW joints were investigated. Compared to the weld metal, enhanced mechanical properties were achieved in the NZs of both FSW joints. Large cracks apparently propagated along the bainite lath in the coarse grains of the weld metal, which would cause the brittle quasi-cleavage fracture. However, large crack propagation was inhibited in the refined bainite phase structure in the NZ of FSW-a joint, and enhanced strength and toughness with dimple fracture were achieved. Meanwhile, enhanced mechanical properties, including strength and ductility, as well as toughness, were obtained in the NZ of FSW-b joint, because of the refinement of the ductile ferrite structure.