Study on the Size Effects of H-Shaped Fusion Zone of Fiber Laser Welded AZ31 Joint

Abstract

There are two kinds of typical cross-section profiles for the fusion zone (FZ) of a laser welded thin section joint, i.e., a V-shaped cross-section and an H-shaped cross-section. Previous researches indicated that tensile strength of the V-shaped joint was lower than that of the H-shaped one due to the greater heterogeneity of strain distribution on the V-shaped joint during tensile process. In this work, impacts of the aspect ratio of FZ on the mechanical properties of laser welded thin section joints with an H-shaped cross-section profile were investigated. Welding conditions corresponding to two typical H-shaped joints (i.e., W narrower with a narrower FZ, and W wider with a wider FZ) were decided through a laser welding orthogonal experimental plan. Then, the microstructure and properties of both joints were examined and compared. The results show that the tensile strength of joint W narrower and joint W wider was about 72% and 80.9% that of the base metal, respectively. Both joints fractured in the FZ during tensile processes. The low-cycle fatigue life of the base metal, the joint W narrower and the joint W wider were 3377.5 cycles, 2825 cycles and 3155.3 cycles, respectively. By using high-speed imaging, it was found that the fatigue crack of joint W narrower initiated and propagated inside the fusion zone, while the fatigue crack of the joint W wider initiated at the edge of the base metal and propagated for a distance within the base metal before entering into the fusion zone. This work promoted our understanding about the influence of the weld bead shape on the properties of laser welded thin section joints.

Laser Welding

“…The present special issue on "Laser Welding" was a success with a total of 16 original research works published after peer-review. Different topics were discussed within this special issue: modelling and simulation of laser welding were presented in [1][2][3][4]; porosity control by means of high speed imaging and microscopy techniques was studied and discussed [5]; the effect of processing parameters on the microstructure and mechanical properties of laser-welded joints was evaluated for different metallic systems such as AZ31 alloy [6], steels [7][8][9][10], Ti-based alloys [11][12][13], and Al-based alloys [14]; and finally, dissimilar laser welding of aluminum to steel was presented [15,16].…”

Numerical Simulations and Experimental Validation on LBW Bead Profiles of Ti-6Al-4V Alloy

“…Advanced research is directed towards development of modeling and simulation tools, in addition to the process control in welding metallurgy (Wu et al, 2018;Ruan et al, 2018;Dal & Peyre, 2017;D'Ostuni et al, 2017;Popescu et al, 2017). Extensive studies are made on laser weld joint properties of metallic materials such as Al-based alloys (Zhang et al, 2017), AZ31 alloy (Lu et al, 2018), Al-steel (Cui et al, 2017;Casalino et al, 2017), steels (Górka & Stano, 2018;Mohammed et al, 2017;Xue et al, 2017;Evin & Tomáš, 2017), and Ti-based alloys (Zeng et al, 2017;Sánchez-Amaya et al, 2017;Caiazzo et al, 2017b). Mashinini & Hattingh (2018) have utilized LBW for joining 3 mm thick Ti-6Al-4V alloy sheets.…”