Deciphering the intrinsic material properties on milling mechanisms of Ti-modified AlCoCrFeNi₂.₁ high-entropy alloy

Abstract

As a typical category of high-entropy alloys, eutectic high-entropy alloys (EHEAs) are distinguished by their near-equiatomic compositions and distinctive lamellar microstructures, which offer an optimal balance of strength, ductility, thermal stability, hardness, and toughness, making them ideal for structural and machining-intensive applications. However, milling mechanisms on EHEA with multiple phases and complex textural characteristics are still unclear, particularly regarding tool wear and surface quality. This study addresses how Ti additions to AlCoCrFeNi<inf>2</inf>.<inf>1</inf> EHEAs modify microstructural characteristics and micro-milling performance. Ti promotes a transformation from lamellar to BCC-dominated equiaxed microstructures, accompanied by L1<inf>2</inf>/B2 ordered precipitates, increasing hardness and altering ductility. Crucially, the product of ultimate tensile strength and elongation (UTS × TE) governs tool wear mode: alloys with higher UTS × TE promote adhesive wear due to stronger interfacial bonding and enhanced FCC texture. As Ti content increases, wear transitions from adhesion-dominated to abrasion-driven mechanisms, correlating with evolving microstructure and cutting dynamics. These findings establish mechanistic links between phase evolution, mechanical behavior, and milling performance—offering new guidelines for machining multiphase HEAs with optimized tool longevity and surface quality.