Effect of Ta Addition on Microstructure and Hardness of FeCrNiMnCoTa_x and Al_0.5FeCrNiMnCoTa_x High-Entropy Alloys

Abstract

Phase formation, microstructure, and hardness properties of FeCrNiMnCoTax and Al0.5 FeCrNiMnCoTax high-entropy alloys (HEA) have been investigated and reported. In this study, FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax high-entropy alloys (HEA) were synthesized using arc-melting technique in argon (Ar) atmosphere from high purity elements (x in molar ratio, x=0.2, x=0.4 and x=0.6). Ingots from arc-melting were homogenized for 24h at 900°C in Ar atmosphere. Dominant dendritic and inter-dendritic phases were identified from the electron micrographs of these HEA. The area of inter-dendrite region increased for both FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys with the increasing of Ta content. The major phases in both FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys were identified as FCC and BCC solid-solutions. Addition of Al in Al0.5FeCrNiMnCoTax alloys has resulted in precipitation of a minor phase which was identified as FCC-TaCr2 Laves phase. As the Ta content increased, hardness of FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys increased from 200.34 Hv to 345.10 Hv and 385.22 Hv to 570.86 Hv respectively. Furthermore, presence of Laves phase in Al0.5FeCrNiMnCoTax alloys has resulted in higher hardness values compared to Al free sample, and this higher hardness could be attributed to precipitation strengthening effect by Laves intermetallic phase formation.

Bio-high entropy alloys: Progress, challenges, and opportunities

“…In contrast, high Ti concentration leads to the precipitation of intermetallic compounds in HEAs to embrittle the alloy ( Zhou et al, 2007 ). The strengthening mechanism of element Ta ( Mohd Pauzi et al, 2016 ) for Al 0.5 FeCrNiMnCo (the primary phase is BCC + FCC) is mainly characterized by the precipitation strengthening effect and the presence of more Laves intermetallic phase precipitation. In addition, the strengthening effects of W ( Waseem and Ryu, 2017 ), Zr ( Yurchenko et al, 2017 ), and Cr ( Stepanov et al, 2015 ) in Bio-HEAs were analyzed separately, and the compressive and tensile strengths increased to varying degrees with the addition of small amounts of the elements.…”

Combinatorial Design of Novel Multiprincipal Element Alloys Using Experimental Techniques

“…[21,[43][44][45][46][47][48][49][50] Indeed, former studies suggested that VEC has a deterministic effect on the types of phases formed in different MPEA systems. [51][52][53] Namely, when VEC is higher than about 8, an fcc phase forms while when VEC is lower than about 7 the stable phase has a bcc structure. Between these two VEC values, fcc and bcc phases coexist.…”