Slip behavior of Bi-modal structure in a metastable β titanium alloy during tensile deformation

• 作者: Wenguang Zhu Changsheng Tan Ruoyu Xiao Qiaoyan Sun Jun Sun
• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2020,（22）
• 页码范围: 188-196
• 页数: 9页
• 语种: 英文

摘要

β titanium alloys with bi-modal structure which exhibit improved strength-ductility combination and fatigue property are widely used in aviation and aerospace industry.However,owing to the small size of primary α (αp) and nano-scaled multi variant distribution of secondary α platelets (αs),investigating the deformation behavior is really a challenging work.In this work,by applying transmission electron microscopy (TEM),the slip behavior in αp and transformed β matrix with different tensile strain was studied.After α/β solution treatment,the initial dislocation slips on { 110} plane with 〈1(1)1 〉 direction in β matrix.During further deformation,(110),(101) and (1(1) 2) multi slip is generated which shows a long straight crossing configuration.Dislocation cell is exhibited in β matrix at tensile strain above 20 ％.Differ-ent from the solid solution treated sample,high density wavy dislocations are generated in transformed β matrix.High fraction fine αs hinders dislocation motion in β matrix effectively which in turn dominates the strength of the alloy.In primary α phase (αp),a core-shell structure is formed during deformation.Both pyramidal a + c slip and prismatic/basal a slip are generated in the shell layer.In core region,plastic deformation is governed by prismatic/basal a slip.Formation of the core-shell structure is the physical origin of the improved ductility.On one hand,the work hardening layer (shell) improves the strength of αp,which could deform compatibly with the hard transformed β matrix.Meanwhile,the center area(core) deforms homogeneously which will sustain plastic strain effectively and increase the ductility.This paper studies the slip behavior and reveals the origin of the improved strength-ductility combination in Bi-modal structure on a microscopic way,which will give theoretical advises for developing the next generation high strength β titanium alloys.