Li Bolong, Zhou Jiayi, Hu Rongxun, Pan Hua, Wu Tianhai, Gao Yulai
State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China.
Automobile Steel Research Institute, R&D Center, Baoshan Iron & Steel Co., Ltd., Shanghai 201900, China.
Materials (Basel). 2025 Jun 6;18(12):2676. doi: 10.3390/ma18122676.
Joining steel and Al alloys can fully utilize their advantages for both base metals (BMs) and optimize automobile structures. In this study, the laser welding-brazing technique was utilized to join DP780 steel and aluminum alloy 5754 (AA5754). The mechanical properties, microstructure, and fracture locations of steel-Al joints prepared using different laser spot positions were comparatively investigated. As the proportion of the laser spot on the steel BM increased from 50% to 90%, the tensile-shear strength of the steel-Al welded joint rose from 169 MPa to 241 MPa. Meanwhile, the fracture location of the joint shifted from the interface to the BM of the aluminum alloy. The change in the laser spot position could dramatically affect the interfacial microstructure and fracture mode of the steel-Al joint. When the proportion of the laser spot on the steel BM was relatively small (50%), the growth of intermetallic compounds (IMCs) was inhibited. The metallurgical bonding effect at the steel-Al interface was poor. In this case, the interfacial zone became the primary path for the crack propagation. Thus, interface failure became the dominant failure mode of the steel-Al joint. On the contrary, metallurgical bonding at the interface was remarkably improved as the proportion of the laser spot on the BM of the steel increased (to 90%). It was determined that the IMCs could effectively hinder the propagation of cracks along the interface. Eventually, the joint fractured in the Al alloy's BM, resulting in a qualified steel-Al joint.
将钢与铝合金连接起来可以充分利用两种母材的优势，从而优化汽车结构。在本研究中，采用激光熔钎焊技术连接双相780钢（DP780）和5754铝合金（AA5754）。对使用不同激光光斑位置制备的钢 - 铝接头的力学性能、微观结构和断裂位置进行了对比研究。随着激光光斑在钢母材上所占比例从50%增加到90%，钢 - 铝焊接接头的拉伸剪切强度从169 MPa提高到241 MPa。同时，接头的断裂位置从界面转移到铝合金母材。激光光斑位置的变化会显著影响钢 - 铝接头的界面微观结构和断裂模式。当激光光斑在钢母材上的比例相对较小时（50%），金属间化合物（IMC）的生长受到抑制。钢 - 铝界面处的冶金结合效果较差。在这种情况下，界面区域成为裂纹扩展的主要路径。因此，界面失效成为钢 - 铝接头的主要失效模式。相反，随着激光光斑在钢母材上的比例增加（至90%），界面处的冶金结合得到显著改善。结果表明，金属间化合物能够有效阻碍裂纹沿界面扩展。最终，接头在铝合金母材处断裂，形成了合格的钢 - 铝接头。
