Effect of Ta addition on solidification characteristics of CoCrFeNiTax eutectic high entropy alloys

Abstract

Effect of Ta addition on solidification characteristics of CoCrFeNiTax (x = 0.1–0.7) eutectic high entropy alloys were investigated. With increasing Ta content, CoCrFeNiTax alloys changed from hypoeutectic alloys with primary γ phase to eutectic alloy (x = 0.43) and to hypereutectic alloys with primary Laves phase. Consequently, Ta content in primary phase significantly increased, while the content of Ta element in γ/Laves eutectic phases slightly decreased. Meanwhile, the solidification path and solidification characteristic temperatures of CoCrFeNiTax alloys both agreed with typical binary eutectic phase diagram, and obvious microsegregation of Ta element was only found in CoCrFeNiTa0.1 alloy. Furthermore, the contents of Co, Cr, Fe and Ni elements in primary phases and distribution behaviors of Co, Cr, Fe and Ni elements were both different in CoCrFeNiTax alloys, which indicated that CoCrFeNiTax alloys cannot be simplified as (CoCrFeNi)–Ta pseudo binary system when analyzing distribution behaviors of Co, Cr, Fe and Ni elements.