Architected Multi‐Phase Structure of CoNiTa Compositionally Complex Alloy for Synergistic Strength and Wear Resistance

ABSTRACT

CoNi‐based compositionally complex alloys (CCA), such as CoNiV, are recognized for their remarkable mechanical properties, especially with excellent wear resistance, becoming increasingly essential for ensuring their stability in demanding operational environments. In this study, a novel multiphase structure was architected in CoNiTa CCA, designed by substituting V with Ta to introduce severe lattice distortion and lower stacking fault energy. The as‐designed alloy exhibits a remarkable combination of high hardness (9.19 GPa), approximately three times that of the CoNiV baseline alloy, and an ultralow wear rate of 2.83 × 10 ⁻⁷  mm ³ N ⁻¹ m ⁻¹ under humid conditions (70% relative humidity (R.H.)). Comprehensive microstructural characterization reveals that the superior performance originates from the synergistic effects of a strengthened eutectic nested framework, consisting of face‐centered cubic (FCC) phases and lamellar Ni ₃ Ta precipitates, together with a protective tribo‐oxide layer formed during sliding. Surface analyses demonstrate that pronounced tribochemical reactions occur, leading to the formation of a nearly continuous oxide layer composed of three distinct metal oxides on the worn surface, which effectively suppresses material removal. This work architecturally constructs a kind of medium entropy alloy with multiphase structures and provides a viable pathway to achieve synergistic mechanical and tribological properties for demanding structural applications.