Excellent room-temperature tensile ductility in as-cast Ti37V15Nb22Hf23W3 refractory high entropy alloys. (December 2022)

• Record Type: Journal Article
• Authors: Huang, Wenjun; Hou, Jinxiong; Wang, Xuejiao; Qiao, Junwei; Wu, Yucheng
• Is Part Of: Intermetallics. Volume 151(2022)
• Publication Date: 2022-12
• Subjects: Refractory high entropy alloy (RHEA) -- Mechanical properties -- Solid solution strengthening -- Tungsten; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2022.107735
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: An as-cast Ti37 V15 Nb22 Hf23 W3 refractory high entropy alloy (RHEA) with outstanding tensile properties designed by the natural mixing method and solid solution strengthening theoretical model is reported. The current as-cast RHEA presents a random solid solution with a body-centered cubic (BCC) crystal structure and inherits the natural-mixing characteristics. Interestingly, When compared to the W-free Ti38 V15 Nb23 Hf24 RHEA, minor addition of 3 at. % W atoms increases the yield strength by 26.6% to 980 − 19 + 17 MPa while preserving 19.8 − 0.5 + 0.5 % tensile ductility at room temperature. Toward a better understanding of high yield strength, a solid solution model is proposed to explain strong strengthening, and the experimental value is in good agreement with the theoretical one, indicating the significant solid solution strengthening effect in strengthening the RHEAs. The widespread planar dislocation glide favors the production of complicated dislocation structures (e.g., jogs, dipoles, and loops) as well as dense dislocation networks, which can further obstruct dislocation motion meanwhile effectively relieving stress concentration. The dislocation tangles, loops, dipoles, and jogs together with their interactions postpone the local deformation, results in the excellent ductility. Highlights: As-cast Ti37 V15 Nb22 Hf23 W3 RHEA with excellent mechanical properties was successfully designed by the natural mixing method. The RHEA inherits characteristics of natural mixing, with excellent mechanical properties (σ=980 MPa, and ε=19.8 %). It is found that the multiple dislocation band cross-slip is mainly responsible for the excellent tensile ductility. The yield strength can be explained by a theoretical model of solid solution strengthening, which is in a good agreement with the experimental one.