{10 1 over line 2} twinning induced by the interaction between {11 2 over line 1} twin and β phase in α plus β Ti alloys

Severe plastic deformation induces numerous deformation twins in fully lamellar alpha+ beta Ti alloys. Interaction between deformation twins and beta phase brings a strong strengthening effect, however, the twinning transfer mechanism across alpha/ beta interface is still unclear. In this work, we report the interaction behavior and transfer mechanism of {11 2 over line 1} twin across alpha/ beta interface. Different from the common case that twinning strain transferred by plastic deformation of beta phase, the interaction between {11 2 over line 1} twin and beta phase induces {10 1 over line 2} twinning around the interaction area and the beta phase is free of plastic deformation. Experiments show that {10 1 over line 2} twins will nucleate in four quadrants of the intersection between {11 2 over line 1} twin and beta phase when the beta phase is thicker, whereas {10 1 over line 2} twins will only nucleate in one pair of diagonal quadrants of the intersection when the beta phase is thinner. The reason is that the strain field around the intersection between {11 2 over line 1} twin and beta phase is correlated with the thickness of beta phase, which ultimately determines where {10 1 over line 2} twins nucleate. Moreover, transmission electron microscopy (TEM) investigations reveal that the beta phase will block the motivation of {11 2 over line 1} twinning dislocation b { 11 2 over line 1 } t . In this situation, the twinning transfer of {11 2 over line 1} twin through the beta phase is accomplished with the help of elastic deformation of beta phase and nucleation of sequential {10 1 over line 2} twins. The {10 1 over line 2} twinning is facilitated by the dissociation of b { 11 2 over line 1 } t dislocations at the alpha/ beta interface promoted by the {11 2 over line 1} twinning shear stress field at the interaction area. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.