Mechanical properties and microstructures of Mg-6Si alloys fabricated using the tungsten-inert-gas arc additive manufacturing

• WAAM significantly refines the Mg2Si phase and grain size, leading to a 36.6% increase in microhardness and 63.4% improvement in room-temperature tensile strength compared to as-cast Mg-6Si alloy. • The granular Mg2Si phase becomes finer and more uniformly distributed, while the detrimental acicular Mg2Si phase is reduced, contributing to enhanced mechanical properties. • The rapid cooling inherent in WAAM promotes a homogeneous microstructure, offering a promising route for producing high-performance Mg-Si alloys for engineering applications. • This study provides practical guidance for optimizing additive manufacturing parameters to control intermetallic phase morphology in magnesium alloys.