Investigation of laser beam welding on lap joints of Al/steel dissimilar materials subjected to alternating magnetic field

Abstract

In this study, magnetically assisted laser beam welding was experimentally carried out on Al/steel dissimilar materials in a lap configuration. Weld morphology, interfacial microstructure, element distribution, precipitated phases and mechanical properties of laser-welded joints were carefully investigated. The strengthening mechanism of Al/steel joints was also explored. The results revealed that good weldments were successfully acquired with the assistance of an alternating magnetic field. The microstructures at interface were mainly constituted by nubbly structures, island-shaped structures and banded structures. Fe-Al compounds at interface were expectedly dispersed due to the magnetic field-driven effect on liquid metal. During laser beam welding, the susceptibility to weld cracking was obviously decreased on the premise of inhibition of the composition segregation. The Fe/Al interface zone was mainly composed of η-Fe2Al5 phase, β2-FeAl phase, ζ-FeAl2 phase and θ-FeAl3 phase. The maximum tensile load and elongation of the tested joints subjected to a magnetic field reached 122.22 % and 145.76 % of joints without magnetic field, respectively. Performance enhancement of welded joints was mainly attributive to the effective regulation of weld microstructure and composition during magnetically assisted laser beam welding.