Effects of Si Addition on Microstructure, Properties and Serration Behaviors of Lightweight Al-Mg-Zn-Cu Medium-entropy Alloys

Abstract

A series of as-cast lightweight multicomponent alloys Al(86-x)Mg10Zn2 Cu2 Six (x=0, 0.3, 0.6, 0.9, 1.2 at.%) were prepared by a vacuum induction furnace with a steel die. With the addition of Si, the reticular white Al-Cu phase deposited were gradually replaced by the gray eutectic Mg-Si phase, while the compressive strength of the alloys increases first and then decreases slowly. It is particularly noteworthy that the compression plasticity also exhibits this trend. When the Si content is 0.9 at.%, the compressive strength reaches its maximum at 779.11 MPa and the compressive plasticity reaches 20.91%. The effect of the addition of Si on the serration behavior of alloy was also studied; we found that the addition of Si introduces a new MgSi phase, and with the change of Si is significantly affects the morphology of the precipitated phase, which affects the serration behavior of the alloys. The comprehensive mechanical properties of the alloy are optimal at the critical point where the serration behavior disappears.In this work, we have provided a method and a composition for the preparation of a low-cost, high-strength, lightweight medium-entropy alloys.