钢/铝激光焊接接头性能与金属间化合物延/脆性的第一性原理和实验研究

First-principles and experimental investigations on ductility/brittleness of intermetallic compounds and joint properties in steel/aluminum laser welding

采用扫描电子显微镜、能谱仪、X射线衍射仪以及第一性原理计算方法,研究钢/铝激光焊接形成的金属间化合物(IMCs)的形貌、分布、相组成、形成能力、结构稳定性和本征力学性质。结果发现,脆性Fe−Al化合物限制钢/铝接头力学性能,其脆性电子结构根源在于Al(s)、Al(p)和Fe(d)之间的轨道杂化;添加中间夹层可改善钢/铝接头的力学性能,归因于形成的金属间化合物电子结构的改变;金属间化合物由脆性向延性的转变机制主要归因于夹层元素吸引电子的能力弱。钢/铝焊接头的力学性能与金属间化合物的延/脆性密切相关,添加Ti箔有效提高接头的力学性能,表明实验验证与理论计算预测吻合较好。

Morphology,distribution,composition,forming ability,structural stability and intrinsic mechanical properties of the intermetallic compounds(IMCs)formed in steel/aluminum laser welding were determined through scanning electron microscope,energy dispersive spectrometer,X-ray diffractometer and first-principles calculation.It was found that the mechanical properties of the joint are limited by the Fe−Al IMCs,whose brittleness is attributed to the orbital hybridization between Al(s),Al(p)and Fe(d).However,the joint properties are improved by adding interlayer,which is ascribed to some changes of electronic structure of the generated IMCs.The transition mechanism of IMCs changing from brittle to ductile is mainly due to the weak ability of interlayer elements to attract electrons.The mechanical properties of the joint are closely related to the ductility or brittleness of the IMCs.Moreover,the addition of Ti foil interlayer effectively improves the mechanical properties of the joints,which means that the experimental verification is in good agreement with the theoretical calculation predictions.