Influence of Heat Treatment on The Structural and Mechanical Properties of Cold-Worked AL-3MG-2SI-0.5NI Alloy System

Abstract

This study investigated the effects of heat treatment on the structural and mechanical properties of an Al-3wt%Mg-2wt%Si-0.5wt%Ni alloy system. The alloy samples were produced using a permanent die-casting technique and subsequently machined to the required dimensions for mechanical testing and microstructural analysis. Mechanical properties, including ultimate tensile strength, percentage elongation, hardness, and impact strength, were evaluated using a 100 kN JPL tensile testing machine (Model: 130812), a dynamic hardness tester, and an impact testing machine (Model: U1820). Microstructural characterization was conducted using an optical metallurgical microscope (Model: L2003A) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Microstructural analysis revealed that the as-cast control sample exhibited coarse microsegregation of the intermetallic Mg₂Si phase. In contrast, the solution heat-treated samples showed uniformly distributed fine Mg₂Si intermetallic particles throughout the alloy matrix. Mechanical test results demonstrated that heat treatment significantly improved the ultimate tensile strength, impact strength, and percentage elongation of the alloy. These improvements were attributed to the fine dispersion of Mg₂Si particles within the alloy structure. Furthermore, heat treatment reduced the microsegregation of Mg₂Si by minimizing solute redistribution of Mg, Ni, and Si within the matrix. However, the control sample exhibited the highest hardness value due to the presence of coarse intermetallic Mg₂Si compounds in the alloy structure. The findings of this study highlight the significant role of heat treatment in enhancing the structural refinement and mechanical performance of Al-Mg-Si-Ni alloy systems for engineering applications.