Texture evolution related to static recrystallization during annealing of TA15 alloy tube formed by flow forming

Abstract

In this work, the static recrystallization (SRX) responsible for texture development during the annealing of the TA15 flow-formed part was investigated by comparatively analyzing the SRX microstructure and texture under different pre-strains and annealing temperatures. The results indicated that SRX grains are produced by discontinuous (DSRX) and continuous (CSRX) mechanisms, while the dominant mechanism depends on the pre-deformation and annealing conditions. At a smaller pre-strain, DSRX is prevalent, and some DSRX grains whose {11–20} axes are parallel to the normal direction preferentially grow via the long-range migration of 60–90° grain boundaries. With increased pre-strain, the dominant mechanism gradually changes from DSRX to CSRX. At a larger pre-strain, the CSRX always prevails. Most CSRX grains have an orientation similar to deformed grains which exhibit non-standard basal texture. However, CSRX grains related to deformation-induced intense and localized shearing (CSRX-DILS) show different orientations. The occurrence of DSRX and CSRX-DILS has a minor effect on global annealing texture type owing to the lower fraction but only weakens its concentration. Most CSRX grains primarily affect the texture intensity based on their growth rate. At a pre-strain of 3.36, a higher misorientation angle induced by flow forming can accelerate the growth of CSRX grains, thereby forming an intense CSRX texture and consequently strengthening the global texture. However, the CSRX grain growth at 6.10 pre-strain is limited, resulting in a weaker global texture. With the above effects by SRX, the global annealing texture inherits the features of deformation texture, i.e., non-standard basal texture, but its intensity decreases.

Keywords

• Titanium alloy
• Texture evolution
• Static recrystallization
• Flow forming