Effect of the valence electron concentration on the yield strength of Ti–Zr–Nb–V high-entropy alloys

• Published in: Journal of alloys and compounds 2021-07, Vol.868, p.159190, Article 159190
• Main Authors: Wang, Jie, Bai, Shuxin, Tang, Yu, Li, Shun, Liu, Xiyue, Jia, Jinhao, Ye, Yicong, Zhu, Li’an
• Format: Article
• Language: English
• Subjects: Alloys; Bonding strength; Electron backscatter diffraction; Elongation; High entropy alloys; Mechanical properties; Niobium; Solid solutions; Titanium; Ti–Zr–Nb–V; Valence electron concentration; Vanadium; Yield strength; Yield stress; Zirconium
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.159190

•A quantitative relationship between yield strength and valence electrons concentration (VEC) of HEAs was proposed firstly.•The above relationship was revealed through the cohesive energy between constituent atoms.•Mechanisms for the presence of Laves phase in Ti–Zr–Nb–V alloys with high V/Zr ratio were revealed.•As-cast Ti25Zr25Nb25V25 alloy with moderate VEC presented a tensile yielding strength of 876MPa and an elongation of 20.7%. [Display omitted] To reveal the effect of the valence electron concentration on the yield strength of high-entropy alloys (HEAs), a series of Ti–Zr–Nb–V HEAs with the same atomic size mismatch were designed and prepared. Experimental results including X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) show that the alloys with a low V/Zr ratio presents a single-phase body-centred cubic (BCC) solid solution structure, while a small amount of V2Zr phase appears in the alloys with a high V/Zr ratio. The Ti25Zr25Nb25V25 alloy presented high mechanical properties (tensile yield strength σy = 876 MPa and elongation of 20.7%), and the yield strength of the Ti–Zr–Nb–V alloys increases with an increasing V/Zr ratio. Based on the analysis of all of the potential strengthening mechanisms and the intrinsic strength of the solution alloy with the metallic bonds, a positive linear relationship was proposed between the intrinsic strength and the product of the square of the valence electron concentration and the inverse of the average atomic size.