β-Ti Grain Refinement Via α-Precipitation
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The present work explores the impact of α precipitates on β recrystallization following hot deformation of Ti-5Al-5Mo-5V-3Cr with grains larger than 1 mm. A single hot rolling pass of 36 pct reduction was conducted on an aged microstructure containing α precipitates at a temperature well below the β transus temperature. After annealing, a uniformly recrystallized structure with a grain size of ~100 µm is formed. The prior β grain boundaries can be readily identified and it is seen that the primary β grains have been replaced by grains displaying a spread of correlated misorientation angles extending up to the highest allowable values. The annealing comprises two stages. The first stage involves normal β subgrain growth limited by the Zener pinning force of the unstable α precipitates. The second stage corresponds to the onset of β recrystallization at the point where the Zener pinning force drops due to dissolution of the α precipitates. This leads to a uniform distribution of site saturated recrystallization nuclei.
KeywordsRecrystallization Misorientation Angle Subgrain Size Cube Orientation Thin Black Line
The authors gratefully acknowledge the financial support from the Australian Research Council through the Centre of Excellence for Design in Light Metals, and use of the Deakin Advanced Characterisation Facility. Also, thanks to Mr Lynton Leigh for his assistance in the heat treatment and rolling process.
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