title: Origin of ultralow Young׳s modulus in a metastable β-type Ti-33Nb-4Sn alloy.
abstract: Although there is difficulty in growing a Ti-33Nb-4Sn single crystal due to its ultralow β-phase stability, the single-crystal elastic constants of metastable β-type Ti-33Nb-4Sn (wt%) alloy were extracted successfully from its polycrystal by in-situ synchrotron X-ray diffraction technique, to clarify the origin of the ultralow Young's modulus in its polycrystal. It is indicated that compared to binary TiCr, TiV and TiNb alloys, the Ti-33Nb-4Sn alloy possesses slightly lower β-phase stability with respect to {110}<110>(-)shear (i.e., C׳) but much lower β-phase stability regarding to {001}〈100〉 shear (i.e., C44). An analysis by the Hill approximation suggests that the ultralow isotropic polycrystalline Young׳s modulus (EH) of Ti-33Nb-4Sn alloy originates from the extremely low shear modulus C44 as well as the relatively low C׳. This indicates that in addition to C׳, C44 has a significant contribution to the Young's modulus of polycrystal, which challenges a conventional understanding that the Young's modulus of β-type Ti alloys is predominantly determined by C׳.
authors.affiliation: Institute for Advanced Materials, Jiangsu University, Zhenjiang 212013, China.
authors.forename: Y P
authors.initials: YP
authors.lastname: Hou
authors.affiliation: Institute for Advanced Materials, Jiangsu University, Zhenjiang 212013, China; Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology, Nanjing 211167, China. Electronic address: shunguo@ujs.edu.cn.
authors.forename: S
authors.initials: S
authors.lastname: Guo
authors.affiliation: School of Materials Science and Engineering, Beihang University, Beijing 100191, China.
authors.forename: X L
authors.initials: XL
authors.lastname: Qiao
authors.affiliation: Institute for Advanced Materials, Jiangsu University, Zhenjiang 212013, China.
authors.forename: T
authors.initials: T
authors.lastname: Tian
authors.affiliation: School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou 221116, China. Electronic address: qkmeng@cumt.edu.cn.
authors.forename: Q K
authors.initials: QK
authors.lastname: Meng
authors.affiliation: Institute for Advanced Materials, Jiangsu University, Zhenjiang 212013, China.
authors.forename: X N
authors.initials: XN
authors.lastname: Cheng
authors.affiliation: School of Materials Science and Engineering, Beihang University, Beijing 100191, China. Electronic address: xinqing@buaa.edu.cn.
authors.forename: X Q
authors.initials: XQ
authors.lastname: Zhao
mesh_terms: D000497:Alloys / Q000737:chemistry*; D055119:Elastic Modulus; D008422:Materials Testing; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000497:Alloys; D014025:Titanium
keywords: Elastic behavior; In-situ synchrotron X-ray diffraction; Metastable β Ti alloy; Young׳s modulus