Insights on mechanical properties of dual-phase high entropy alloys via Y introduction

AlCoCrFeNi high entropy alloy (HEA) with a dual-phase A2+B2 structure has received significant research interests due to its favorable mechanical properties. In order to further optimize the mechanical properties of the dual-phase AlCoCrFeNi HEA, we design several types of (AlCoCrFeNi)100-xYx (x = 0, 0.05, 0.1, 0.5 and 1, at%) HEAs and explore the microstructure evolution as well as mechanical behaviors as a function of the Y addition. Adding Y element into the (AlCoCrFeNi)100-xYx HEAs tailors the phase composition, where Y-0.05 HEA is of the single BCC solid solution, similar to Y-0 HEA. And when Y addition is equal to or higher than 0.1 at%, (Ni, Y)-rich HCP phase is identified except for the BCC phase, coinciding with a δ-Ω phase selection model. Meanwhile, Y introduction can lighten the intragranular dendrite segregation. The volume fraction of HCP phase follows a growing trend from 0 vol% to 10.33 vol% with an increment of Y introduction, which is beneficial to enhancing the yield strength (from 1302 to 1447 MPa) and microhardness (from 517 to 597 HV). Furthermore, the fracture mechanism from a transgranular fracture mode to an intergranular fracture mode is also revealed.