Co-deformation and dynamic annealing effects on the texture development during alpha-beta processing of a model Zr-Nb alloy

The in-service properties and performance of dual-phase Zr and Ti alloys depend on their crystallographic texture, which develops during hot-working and is affected by interactions between the alpha and beta phases during deformation, annealing and phase transformation. Recent work on hot-rolled Zr-2.5Nb has shown that the texture of the two phases are related, with coupled strengthening of the alpha near {1120} <1010>, which produces strong 0002 pole intensities along the transverse direction, and beta with {001} <110> rotated cube, particularly when the relative volume fraction is around 50:50. To investigate the origin of this texture coupling, we studied a hot-rolled model Zr alloy with 7 wt.% Nb, in which the as-deformed alpha+beta microstructure is preserved on cooling. The alloy was hot-rolled to different reductions at 725 degrees C, which corresponds to a relative alpha:beta volume fraction of 30:70, where the characteristic textures are known to develop quickly at first and then weaken with further reduction. The rolled material was characterised using both 2D and 3D electron backscatter diffraction (EBSD). This analysis uncovered evidence that both recrystallization and phase transformation cause the disappearance of specific avariants during rolling, favouring the formation of soft primary agrains flattened in <1120> and elongated along <1010> during rolling, which in turn has an effect on surrounding beta orientations, promoting the stronger rotated cube component. At higher reductions, these elongated alpha-grains start to break up, as does the beta surrounding it, forming bands of characteristic coupled textures. These observations imply that non-plasticity effects should be included in models of texture evolution during processing of alpha+beta Zr and Ti alloys. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd.

Automated summary

The texture evolution in dual-phase Zr and Ti alloys plays a crucial role in determining their in-service properties and performance. Studies have shown that during hot-working, there is a coupled strengthening effect between the alpha and beta phases, influencing the alloy's characteristics. Incorporating non-plasticity effects into models of texture evolution is important for processing these alloys effectively.