Effect of Y addition and heat treatment on microstructure and properties of Al-Mg-Si-Y alloy

doi:10.13251/j.issn.0254-6051.2025.02.023

Abstract

Abstract: Al-0.6Mg-0.5Si-xY (x=0, 0.1, 0.2, 0.3, 0.4) alloys were prepared and T6 heat treatment was carried out. The evolution of microstructure, electrical conductivity, and mechanical properties of the alloys after heat treatment were investigated. The results show that AlSiY phases are formed at the grain boundaries of the alloy with Y addition after heat treatment, and granular and rod-like AlSiY phases are precipitated in intragranular mode. The white granular Mg₂Si phases are dispersed in the alloy matrix. After heat treatment, the average grain size of the alloys is increased compared to their as-cast state, but it decreases with the increase of Y addition. After heat treatment, electrical conductivity of the alloys initially increases and subsequently decreases with the increase of Y content. The electrical conductivity reaches the highest value of 55.2%IACS by addition of Y with 0.3%, which is 1.7% higher than that of the as-cast alloy. After heat treatment, an increase in grain size of the alloys results in a reduction of grain boundaries, and the precipitation of solved Si atoms reduces the solid solution distortion, thereby improving the conductivity of the alloys. The tensile strength and hardness of the alloys after heat treatment exceed those of the as-cast alloy, exhibiting an initial increase followed by a subsequent decrease with the addition of Y. The tensile strength and hardness of the alloys reach the highest values of 206.2 MPa and 91.3 HV0.1 respectively by addition of Y with 0.3%, which are 36.6% and 40.5% higher than those of the as-cast alloy. The heat-treated alloys exhibit a significantly reduced elongation compared to the as-cast alloys. The heat treatment promotes a large amount of second phase precipitation in the alloys, thereby improving the strength and hardness of the alloys. However, the reduction in grain boundaries and the augmented presence of precipitated phases contribute to a diminished elongation in the heat-treated alloy compared to the as-cast alloy.

Key words: Al-Mg-Si alloy, Y addition, heat treatment, microstructure, electrical conductivity, mechanical properties

CLC Number:

TG146.2

Bi Xiaoqin, Zhang Sen, Zheng Zeyuan, Qi Yulei, Fu Ying, Xu Qin. Effect of Y addition and heat treatment on microstructure and properties of Al-Mg-Si-Y alloy[J]. Heat Treatment of Metals, 2025, 50(2): 148-154.

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