Reduced hot cracking susceptibility by controlling the fusion ratio in laser welding of dissimilar Al alloys joints
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nggui Lua) Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China; and Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072, People’s Republic of China
Hui-Ping Wang Manufacturing Systems Research Lab, General Motors Global Research & Development, Warren, Michigan 48090, USA
Xiaojie Wang, Haichao Cui, and Xinhua Tang Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China (Received 16 December 2014; accepted 23 February 2015)
With the increasing usage of Al alloys in vehicle manufacture, it is necessary to join dissimilar Al alloys with lap joint. However, hot cracking is a challenging issue due to the chemical composition and thermal tension, which greatly determines the reliability of automobile operation. Among different Al alloys, the series 5000 (Al–Mg) and 6000 (Al–Mg–Si) are widely used. To better understand the hot cracking behavior, various stack ups of AA5754 and AA6013 were laser welded to investigate the effects of process parameters on hot cracking formation. The chemical composition, microstructure, fusion ratio, and fracture morphology of the weld joint were also examined. The results showed that the order of material stacking affected weld’s susceptibility to hot cracking significantly, and the critical process parameters were obtained for tested conditions which could effectively reduce hot cracking. The findings from this work provide guidance for hot cracking prevention in laser welding of dissimilar Al alloys. I. INTRODUCTION
Due to attractive characteristics such as low density and excellent mechanical properties, aluminum alloys have been increasingly used in various industrial applications for light weighting in recent years,1–4 especially in the automotive and transportation sectors.5–7 Traditionally, arc welding or resistance welding techniques are used in joining Al alloys,8–11 some new welding methods such as friction stir welding and laser welding are gradually used in recent decades.12–15 Nowadays, laser welding is becoming more and more popular owing to its advantages such as high power density, large weld depthto-width ratio, narrow heat affect zone, high welding speed, and high production rate.16–18 Nevertheless, some problems may occur during the laser welding process, such as hot cracking, cavities, and porosity.19–21 Among them, hot cracking is one of the crucial defects that easily occurred.22 This is especially true for Al–Mg–Si alloys,
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.64 J. Mater. Res., Vol. 30, No. 7, Apr 14, 2015
in which the amount of Si or Mg content drives the alloys vulnerable to hot cracking during fusion welding processes. Many researchers have focused on different aspects on laser welding of Al alloys, such as mechanical properties, microst
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