Liquation Cracking Susceptibility and Mechanical Properties of 7075 Aluminum Alloy GTAW Joints

In this work, aluminum alloy 7075-T651 was welded by using customized Al-Cu-Si and Al-Cu-Mg-Zn filler wire during gas tungsten arc welding. The liquation cracking susceptibility of the joints was tested under a circular-patch welding experiment. Besides, the temperature vs. solid fraction curves (T-f(S)) was calculated for different samples to reveal the formation mechanism of liquation cracking. The joint was susceptible to liquation cracking if (f(S))(weld) > (f(S))(workpiece) during the cooling stage. The results of the circular-patch welding experiment show that the liquation cracking susceptibility of the joint by using ER5356, Al-Cu(1.5)-Si(4.5), Al-Cu(3.0)-Si(2.5), Al-Cu(4.5)-Si(1.5), Al-Cu(2.3)-Mg(2.3)-Zn(6.6) and Al-Cu(2.2)-Mg(2.0)-Zn(7.8) filler metal is 22.8%, 8.3%, 2.8%, 2.8%, 3.3% and 1.4%, respectively. The mechanical test shows that the data dispersion of the 7075 gas tungsten arc welding joint can be decreased by eliminating the liquation crack.