Effect of martensite on {332} twinning formation in a metastable beta titanium alloy

• Published in: Journal of alloys and compounds Vol. 895; p. 162598
• Main Authors: Xiao, J.F., He, B.B., Tan, C.W.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.02.2022; Elsevier BV
• Subjects: Deformation analysis; Deformation effects; Deformation mechanisms; Heat treating; Martensitic transformations; Metastable beta Ti alloys; Orthorhombic phase; Phase stability; Phase transformation; Phase transitions; Titanium alloys; Titanium base alloys; Twinning; Phase transformation; Phase stability; Twinning; Metastable beta Ti alloys
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.162598

•It is first found the modulated structure in the metastable beta titanium alloys after twinning and martensite deformation. Such novelty phenomenon is ascribed to a possible formation procedure of {332} twin: bcc matrix → {130} modulated structure twin (martensite twin) → {332} twin.•A model for calculating the shear and shuffling for twins is proposed. In such a model, the magnitude of shear and shuffling is calculated based on the twin plane and coordinate of atoms in the cell.•The deformation gradient for twining is also applied to determine the twinning types. In the present alloy, the {112} and {332} twinning systems are demonstrated to be preferential during deformation.•The present work suggests that the formation of {332} twinning is closely related to the modulated structure. Such modulated structure roles as the precursor structure during {332} twinning formation, leading to {332} twinning combing stress-induced martensite. {332}β twinning and stress-induced martensite transformation are two important deformation mechanisms in the metastable beta titanium alloys, which can effectively strengthen the titanium alloys via twinning induced plasticity (TWIP) and transformation induced martensite (TRIP) effect, respectively. For a TWIP + TRIP metastable beta titanium alloy, {332}β twinning and stress-induced martensite can co-exist to improve the mechanical behaviors. However, the underlying mechanism for the co-existence of {332}β twinning and stress-induced martensite is not clear. Here we employed a model metastable beta titanium alloy Ti-2Al-9.2Mo-2Fe (wt%) to reveal the correlation between {332}β twinning and stress-induced martensite. The deformation gradient analysis and magnitude of shuffling needed for twining were utilized to reveal the relationship between {332} twinning and stress-induced martensite. As a result, we found that {332} twinning is a product of the reverse bcc to orthorhombic phase transformation. Such mechanism leads to a strong correlation between {332} twinning and stress-induced martensite, causing the {332} twinning combining stress-induced martensite in the present alloy.