Effect of Iron Content on Hot Tearing of High-Strength Al-Mg-Si Alloy

The effect of iron content on hot tearing of the high-strength Al-Mg-Si alloy was systematically investigated. The alloy with higher content of iron resulted in the severe occurrence of hot tearing during direct chill (DC) casting. Mechanical properties of this alloy in which iron content was changed were investigated during solidification using an electromagnetic induction heating tensile machine. Tensile strength and elongation were discussed in relation with solidification progress of which sequence of crystallization, crystallization temperature of formed phases and their crystallized amount were calculated by a thermodynamic calculation software Thermo-Calc. In order to confirm the calculation results of solidification path, a quenching test also was carried out. Furthermore, by comparing the fracture surfaces of the tensile testing sample and DC billet, the temperature range of crack initiation of the alloy was examined. Comparing the temperature range of crack initiation with the crystallization phase and its crystallization order, iron content influenced hot tearing significantly owing to the crystallization behavior of α(AlFeMn) in high-strength Al-Mg-Si alloy.