Effect of strain rate on tensile characteristics and failure behavior of Al/steel welded joint producing by a laser-MIG composite heating source

Abstract

Studies on dynamic tensile characteristics for Al/steel dissimilar materials are crucial to ensure the integrity and dependability of light-weight structures. In this study, the tensile characteristics and failure behaviors of Al/steel laser-MIG welded-brazed joints were studied. The dynamic fracture mechanisms of the joints are discussed. With the increase in strain rate, the fracture mode and tensile properties of Al/steel joints with reinforcement changed. The joints exhibited two failure modes of heat-affected zone failure at lower strain rates and interface failure at higher strain rates. When the strain rate was 1000 s−1, the increase in dislocation density in the weld reinforcement and diversion of cracks in the intermetallic compound layer significantly enhanced the joint’s properties. The tensile and yield strengths reached 222.6 and 166.6 MPa, 6.5 % and 17.9 % higher than those at a stain rate of 1 s−1, respectively. For Al/steel joints without reinforcement, as the strain rate increased, the crack gradually grew to the Al8Fe2Si phase, leading to a notable enhancement in the joint’s performance. At a strain rate of 500 s−1, the maximum strength of the joint reached 238.3 MPa, representing an increase of 58.9 % in comparison to the strain rate of 1 s−1.