Sn–Sc microalloying-induced property improvement and micromechanisms of an Al–Mg–Si alloy
Dehui Zheng, Jiahai Li, Bo Wei, Tingbin Liang, Zhichao Yang, Zhen Wang, Shuangbao Wang
Abstract
Microalloying is of great importance for the property modulation of lightweight high-strength aluminum alloys. Little is known, however, about the properties and micromechanisms of Al-Mg-Si alloys microalloyed with Sn and Sc. In this work, the property changes of Al-0.5Mg-0.4Si (wt%) alloys induced by 0.1Sn and 0.1Sn-0.1Sc (wt%) additions and underlying alloying mechanisms are revealed by atomic-scale transmission electron microscopy and first-principles calculations. The results show that the Sn-Sc coaddition results in a decreased diameter and an increased number density of the Sc-containing constituent particles of Mg2Si and Mg2(Si,Sn), as compared to the sole Sn addition. The featured Si-site columns in β'', B' and β' structures can be occupied by Sn and Sc. Substantial peak-aging β'' needles with confined cross-sectional coarsening are observed for the Sn-Sc containing alloy compared to the Sn containing alloy. The modified constituent particles and precipitates improve the plasticity and strength of peak-aging Al-Mg-Si-Sn-Sc alloy. The elevated peak-aging corrosion resistance and over-aging thermal stability of Al-Mg-Si-Sn-Sc alloy are associated with the sparse Sc-containing Mg2(Si,Sn) grain boundary precipitates and low strain filed of Al matrix around the β' containing Sn/Sc, respectively. The obtained results are hoped to guide the design of high-performance Al alloys.