Atomic-level study of 1011 deformation twinning in pure Ti and Ti-5at.% Al alloy

H Zhang and BQ Wei and XQ Ou and S Ni and HG Yan and M Song, INTERNATIONAL JOURNAL OF PLASTICITY, 153, 103273 (2022).

DOI: 10.1016/j.ijplas.2022.103273

In this work, pure Ti and Ti-5at.%Al alloy are both cold rolled, and then characterized to observe deformation twins 1011. Many two-layer steps are observed at the 1011 twin boundary (TB) in pure Ti by high- resolution transmission electron microscopy (HRTEM). However, in addition to two-layer steps, a large number of four-layer steps are observed at the 1011 twin boundary in Ti-5at.%Al alloy. To understand the experimental observations, molecular dynamics (MD) simulations are performed to analyze the 1011 deformation twinning at the atomic scale. MD simulations are also showing similar results to the experimental observations in pure Ti and Ti5at.%Al alloy. The two-layer and four-layer steps are twinning dislocations (TDs) with the Burgers ? ? vectors of & frac12;x 4 gamma(2_)9 /3+4 gamma(2)< 1012 > & PLUSMN; 16 < 1210 > (b2) and 4 gamma(2_& nbsp;)& nbsp;9/ 3+4 gamma(2)< 1012 > (b4) by topological analysis, ? respectively. For pure Ti, the twin growth is carried out only by the slip of TDs b ? alloy, twinning is carried out by the gliding of TDs b ? ? b4, the nucleation of the twinning dislocations b sites, such as intersections between the stacking fault (SF) and TB (SF-TB intersection) in Ti-5at.% Al alloy. The SF-TB intersection is a sessile imperfect disconnection, and this defect is immobile, ? 2 and TDs b 2. For Ti-5at.% Al 4. Due to the poor mobility of TDs 4 (4-layer steps) requires some special nucleation ? which leads to high stress at the SF-TB intersections to facilitate the nucleation of TD b element enhances the high density of basal stacking faults (BSFs) and SF-TB intersections at the 4. The Al ? twin-tip, and indirectly promotes the nucleation of TD b element also facilitates the nucleation of matrix dislocations, resulting in twin-dislocation interactions that promote the generation of TDs. 4 in Ti-5at.% Al alloy. In addition, Al

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