In-situ investigation of β/α transformation in β-solidifying γ-TiAl alloys at different cooling rates

We report an in-situ study on b/a transformation of a b-solidifying c-TiAl alloy using high-temperature laser scanning confocal microscopy. Combining the current theories of Ti alloys and a method to distinguish the crystal orientation, the special effect of cooling rate on the nucleation, growth of a phase from b matrix as well as the surface relief in Ti-40Al were researched. The results indicate that Ti-40Al exhibits both sympathetic and interface instability nucleation and grows in the form of Widmannstatten plate and equiaxed grain cooling at 2 IC/min; just interface instability nucleation and Widmannstatten plate growth occur in the alloy at 108 IC/min. Besides, high cooling rate can promote the growth rate of Widmannstatten a plates, whose growth direction is parallel to c lamellar orientation nearly. These findings will provide insight into controlling the orientation and size of lamellar colonies of TiAl alloys to improve mechanical properties. (c) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study investigated the b/a transformation of a b-solidifying c-TiAl alloy at different cooling rates. It was found that high cooling rate can promote the growth rate of Widmannstatten a plates, improving the mechanical properties of the alloy.