Effect of filler wire composition on performance of Al/Galvanized steel joints by twin spot laser welding-brazing method

摘要

A twin-spot laser welding-brazing (LWB) process to join aluminum alloy 6022 and hot-dip galvanized steel in coach peel configuration was reported. A maximum surface roughness and sufficient mechanical strength are the important criteria which are affected by the process parameters during welding to judge the weld quality for some applications, such as the automotive industry. Thus, the influences of the main laser welding-brazing process parameters (laser power, wire feed rate, and scanning speed) on the mechanical strength and surface roughness of welds were studied and analytical models relating the output properties of interest to process parameters were also developed. The response surface methodology (RSM) and desirability function were utilized for optimizing the multi-response LWB process. Finally, validation experiments were conducted on an optimized process condition which exhibited good agreement between the predicted and experimental results. Four different filler wire materials were employed (AlSi12, AISi5, AlSi3Mn1, and ZnAl15). The effects of the wire alloying elements on the microstructure of the weld, weld surface quality, and mechanical resistance were investigated. The measured intermetallic compound, IMC, layer at the Fe/Al interface of joints revealed that AlSi12 filler wire resulted in the thinnest IMC layer at less than 2 mu m; in contrast, this value increased to 7 mu m for joints with ZnAl15 wire. In terms of surface roughness, the lowest (Ra = 0.917 mu m) and highest (Ra = 2.83 mu m) values were achieved by using AlSi3Mn1 and ZnAl15 wires, respectively. Although the Zn-based filler wire offered the maximum tensile resistance around 180N/mm, joints with AlSi12 wire had mechanical resistance of 120 N/mm and lower values of IMC layer thickness and surface roughness. Therefore, AlSi12 filler material is recommended as the laser brazing filler material for joining dissimilar aluminum-galvanized steel coach peel panels in automotive body-in-white (BIW) fabrication applications. (C) 2017 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.