钢/铝激光搭接焊接头的抗拉强度、显微组织及断裂模式

Tensile resistance,microstructures of intermetallic compounds,and fracture modes of welded steel/aluminum joints produced using laser lap welding

通过激光搭接焊实现5052铝合金与DP780双相钢异种金属的连接。对焊接过程的金属蒸气和飞溅进行高速摄像检测,并利用万能试验机对焊接接头进行力学性能测试,分析搭接剪切力随激光焊接参数的变化规律。分别采用光学显微镜和扫描电子显微镜对样品进行表征。通过显微组织观察发现在钢/铝界面形成3种不同的金属间化合物相,即带状Fe2Al5、FeAl2和针状FeAl3,探索在不同的激光热量输入下,搭接抗拉强度、激光参数和失效断裂模式之间的关系。结果表明,钢/铝接头在低热量输入和高热量输入出现两种不同的断裂模式,分别为沿焊缝热影响区和沿铝钢接合界面断面,并均为脆性断裂。此外,发现断裂界面都出现裂纹,且在断裂的微观形态中生成针状簇。

The joining of DP780 steel to Al5052 was conducted by laser lap welding,in which the metal vapor and spatters were monitored by a high-speed camera.A universal testing machine was used to test the mechanical properties of the welded joints,and the changing law of lap tensile resistance with the laser welding parameters was analyzed.Optical microscope and scanning electron microscope were used to observe the macro-structure and micro-structure,respectively.Three different intermetallic compounds(IMCs)phases,i.e.banded Fe2Al5,FeAl2 and needle-like FeAl3 were generated at the steel/Al interface on microscopic observation.The aim of this research is to investigate the relationship among the lap tensile resistance,the welding parameters and the failure mode under different energy densities.Experimental results showed that the steel/Al joints have two different fracture modes at low heat input and high heat input.The failures happened along the heat-affected zone of the weld and along the steel/Al joint interface,respectively.And both of the two failure modes are brittle fractures.Additionally,cracks appeared at the fracture interface,and needle-like particle clusters were found in the fracture microstructure.