Deformation-Induced Grain-Interior α Precipitation and β Texture Evolution during the β-Processed Forging of a Near-β Titanium Alloy

Abstract

The effect of grain-interior α precipitation on the β texture evolution of the near-β Ti-6246 alloy during through-transus forging was investigated in two-step sequential forgings. The microstructure and texture were analyzed using scanning electron microscopy, electron-backscatter diffraction, and X-ray diffraction. The previous β forging was performed at 1253 K at 0.01/s, while the subsequent forging in the (α + β) region was conducted at 1073 K at 0.01/s. The forging in the β region facilitated the penetration of the interior α phase into β grains and reduced the formation of grain boundary α. The {001} texture intensity increased during the forging in the single β region. By contrast, the increase in the {001} texture intensity was moderate at a lower temperature (1073 K) because the Schmid factor (SF) value of the {110} slip system drastically decreased, but those of the {112} and {123} slip systems increased before α precipitation. During α precipitation for all β forging ratios, the {110} slip system was activated, resulting in a lowering of the {001} texture intensity. The lower the forging temperature before interior α precipitation under a constant total forging ratio, the more the {001} texture intensity was suppressed in the final β texture, accompanied by interior α precipitation.

Keywords

• titanium alloy
• hot forging
• texture
• phase transformation
• slip system