In-situ study on γ phase transformation behaviour of γ-TiAl alloys at different cooling rates

gamma-TiAl-based alloys are promising lightweight high-temperature structural materials, and the transformation from the a parent phase to gamma lamellae during the cooling process has a great influence on the microstructures and mechanical properties of TiAl alloys. In this paper, an in-situ observation technique, high-temperature laser scanning confocal microscopy (HTLSCM), was utilized to investigate the continuous cooling transition (CCT) from the a phase in three compositions. The nucleation and growth behaviors of gamma lamellae were studied at several moderate cooling rates. In addition, the processes of helium gas quenching for three alloys were investigated, and the massive transformation was observed in Ti-49Al. CCT diagraphs were concluded for three alloys. The Vickers hardness of TiAl alloys subjected to different cooling rates was tested, and it was found that the hardness of alloys was enhanced with increasing cooling rate due to the refinement of lamellar spacing.

Automated summary

In this paper, the transformation behavior from the α phase to γ lamellae in γ-TiAl alloys during the cooling process was investigated using high-temperature laser scanning confocal microscopy (HTLSCM). The nucleation and growth behaviors of γ lamellae were studied at moderate cooling rates, and the effect of cooling rate on the hardness of the alloys was also examined.