中厚板钛合金涡流搅拌摩擦焊接技术研究
Study on Vortex Flow-Based Friction Stir Welding of Medium-Thick Titanium Alloy Plates
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摘要: 采用W-25%Re合金制作的内套筒、WC-15%Co合金制作的下套筒和直径16.0 mm的TC4钛合金搅拌棒为搅拌工具,对6.0 mm 厚TC4钛合金板材进行涡流搅拌摩擦对接焊,研究焊缝的成形质量、微观组织、磨屑残留情况及力学性能。结果表明,采用转速为700 r/min、焊速为30 mm/min的工艺参数,可以一次性焊透6.0 mm厚的TC4钛合金板材,焊缝表面成形良好;接头搅拌区主要由粗大的片层组织构成,初始β晶粒尺寸沿板厚方向逐渐减小,过渡区呈现双态组织特征,热影响区的组织相较于母材显著粗化;磨屑残留主要分布在焊缝上表面,前进侧主要是W-Re合金的磨屑残留,后退侧为W-Re合金和WC-Co合金的混合磨屑。磨屑提高了焊缝硬度,但后退侧磨屑残留区成为接头的最薄弱区,裂纹率先在此萌生并传播至焊缝底部;接头的抗拉强度最高为1 044.5 MPa,可达到母材的87.8%,但断后伸长率显著降低。Abstract: Vortex flow-based friction stir welding (VFSW) is performed on 6 mm thick TC4 titanium alloy plates using the inner sleeve made of W-25%Re alloy,the lower sleeve made of WC-15%Co alloy and the 16 mm diameter TC4 titanium alloy stirring rod as stirring tools. The weld formation, microstructure, tool debris residue within the weld, and mechanical properties are investigated. The results indicate that under the rolling speed of 700 r/min and welding speed of 30 mm/min, complete penetration of the 6 mm thick TC4 plate is achieved in a single pass, and the weld surface is good. The stir zone primarily consists of coarse lamellar structures. Along the plate thickness direction, the size of the prior β grains decreases gradually. The transition zone exhibits characteristics of a bimodal microstructure. Significant grain coarsening is observed in the heat-affected zone compared to the base material. Tool debris residue is predominantly distributed on the weld top surface. The advancing side residue primarily consists of W-Re alloy debris, while the retreating side contains a mixture of W-Re alloy and WC-Co alloy. The presence of debris can enhance the weld hardness. However, the debris accumulation region on the retreating side becomes the weakest area of the joint, where cracks preferentially initiates and propagates towards the weld root. The maximum tensile strength of the joint reaches 1 044.5 MPa, equivalent to 87.8% of that of the base material, but the elongation after fracture decreases compared to the base material.
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