为提高铜/钢转换接头搭接焊的强度与冶金相容性,提出了异种金属微织构激光焊接法。首先利用超快绿激光在钢基体表面制备微织构,以提高焊接时钢侧界面的浸润性与咬合强度,然后利用脉冲绿激光在微织构表面进行铜/钢熔化搭接焊,最后研究了微织构的形貌、接头组织、结合界面及拉伸性能与断裂机制。结果表明:在较高的激光功率与刻蚀次数下,热烧蚀程度加重,易导致凹槽内部质量恶化;表面织构化对接头组织与抗拉强度具有显著影响,表面织构化可以强化对流传质,增强铜向熔池底部(钢侧)的扩散,有利于形成含铜量更高的α-Fe、γ-Fe固溶体,使得熔池底部的显微硬度更高;当凹槽深度为89.91 μm时,织构化接头的抗拉强度最高,为112.5 MPa,相比未织构化接头提高了19.5%;接头的断裂机制为韧性断裂;接头拉伸性能的提高得益于固溶强化、熔合体积的增大以及涡旋咬合作用。

To improve the overlap welding strength and metallurgical compatibility of copper/steel transition joints, a dissimilar metal microtexture-melting laser overlap welding method was proposed. First, ultrafast green laser was used to prepare microtextures on the surface of the steel substrate to improve the wettability and occlusion strength of the steel side interface during the overlap welding, and then copper/steel fusion overlap welding was performed on different microtextured surfaces by pulsed green laser. The microtexture morphology, joint microstructure, bonding interface, tensile properties and fracture mechanisms were studied. The results show that the higher laser power and etching times, the greater the degree of thermal ablation, which easily leads to the deterioration of the internal quality of the groove. The surface texturization has a significant effect on the joint microstructure and tensile strength, and surface texturization can strengthen convective mass transfer, enhance the diffusion of copper to the bottom of the molten pool (steel side), and help the formation of α-Fe and γ-Fe solid solutions with higher copper content, which makes the microhardness of the bottom of the molten pool higher. When the groove depth is 89.91 μm, the tensile strength of the textured joint is the largest, which is 112.5 MPa, 19.5% higher than that of the untextured joint. The fracture mechanism of joints is ductile fracture. The improvement of tensile properties is due to solid solution strengthening, the increase of fusion volume and the vortex bite.