Effect of T6I6 treatment on dynamic mechanical behaviour of Al-Si-Mg-Cu cast alloy and impact resistance of its cast motor shell

Abstract

The effect of T6I6 treatment on the dynamic mechanical and microstructure behaviour of Al-Si-Mg-Cu cast alloy was investigated using split Hopkinson pressure bar (SHPB), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Besides, the impact resistances of T6I6 and T6 motor shells of new energy vehicles made of Al-Si-Mg-Cu cast alloy were compared using a trolley crash test. The results indicated that the main strengthening-phases of the T6 peak-aged and T6I6 peak-aged alloy were GP zone and β″ precipitates. T6I6 treatment can increase the density and size of β″ precipitates in peak-aged alloy and enhance both its tensile strength (σ_b) and elongation (δ). The dynamic toughness values of T6I6 samples are 50.34 MJ/m³ at 2000 s⁻¹ and 177.34 MJ/m³ at 5000 s⁻¹ which are 20% and 12% higher than those of T6 samples, respectively. Compared with a T6 shell, the overall deformation of T6I6 shell is more uniform during the crash test. At an impact momentum of 3.5×10⁴ kg·m/s, the T6I6 shell breaks down at 0.38 s which is 0.10 s later than the T6 shell.

Keywords

Al-Si-Mg-Cu cast alloy / motor shells / T6I6 treatment / dynamic mechanical behaviour / impact resistance

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