7xxx series aluminum alloys are susceptible to solidification cracking during fusion welding. This study systematically investigates the solidification cracking susceptibility of T-Mg₃₂(AlZn)₄₉-strengthened Cu-free Al-Mg-Zn alloy with a Zn/Mg ratio below 1.0. The alloy is different from η-MgZn₂-strengthened 7xxx series alloys whose Zn/Mg ratios are above 1.0. The crack length of the studied Al-Mg-Zn series alloys is shorter than traditional Cu-free 7xxx series alloys, which corresponds to lower solidification cracking tendency. Welding cracks tend to grow along the continuous eutectic phases during the end of welding solidification, and thus, cracks occur when liquid can no longer hold the constraining stress. According to the results, Al-Mg-Zn series alloys have the narrower eutectic temperature range and narrower mushy zone than 7xxx series alloys. Thus, the constraining stress during solidification is lower than 7xxx series alloys. The liquid fractions of the Al-Mg-Zn series alloys are relatively high than 7xxx series alloys, making it possible to heal micro-cracks during the end of solidification process.

7xxx系列铝合金在熔焊过程中易发生凝固裂纹。本研究系统地研究了Zn / Mg比低于1.0的T-Mg ₃₂（AlZn）₄₉强化无铜Al-Mg-Zn合金的凝固裂纹敏感性。合金不同于η-的MgZn ₂锌/镁比大于1.0的高强度7xxx系列合金。研究的Al-Mg-Zn系列合金的裂纹长度比传统的无Cu 7xxx系列合金短，这意味着较低的凝固裂纹倾向。在焊接凝固结束时，焊接裂纹倾向于沿着连续的共晶相生长，因此，当液体不再能承受约束应力时，就会出现裂纹。根据结果​​，与7xxx系列合金相比，Al-Mg-Zn系列合金具有较窄的共晶温度范围和较窄的糊状区。因此，凝固过程中的约束应力低于7xxx系列合金。Al-Mg-Zn系列合金的液体分数比7xxx系列合金的液态分数高，这使得在固化过程结束时可以治愈微裂纹。