Effect of service environment temperature on fatigue performance of laser-MIG hybrid welded joint of high strength aluminum alloy

Objective The aim is to analyze whether the huge service environment temperature difference will affect the fatigue performance of laser-MIG hybrid welded joint of high strength aluminum alloy for high-speed train, and explore the detailed influence mechanism. Methods The standard fatigue samples were tested in this paper to compare and analysis the fatigue performance at −40 ℃, 25 ℃ and 70 ℃, which were sampled on the laser-MIG hybrid welded joints of an Al-Mg-Si aluminum alloy. The fatigue S-N curves and fatigue strength at three service environment temperatures were obtained and the influence of temperature on fatigue performance of joints was summarized by analyzing fatigue crack sprout and crack propagation. Results The results show that, compared with the fatigue strength of welded joint at room temperature, the low temperature fatigue strength of welded joints at −40 ℃ decreased by 2.7% and the high temperature fatigue strength of welded joints at 70 ℃ decreased by 6.4%. Conclusion Service environment temperature has a certain influence on fatigue crack sprout and crack propagation of laser-MIG hybrid welded joint of aluminum alloy. The effect of service environment temperature on fatigue performance is similar with the increase of stress ratio.