Grain coarsening in Ti – 45Al based titanium aluminides at supertransus temperature and subsequent lamellar structure formation

Abstract

The phenomenon of grain growth in the α phase field and the effect of annealing time/grain size on the formation of lamellar microstructure upon subsequent cooling was studied in Ti - 45Al - 2Nb - 0.4Mn and Ti- 45Al - 2Nb alloys. The grain size of both alloys increased with annealing time and the grain growth exponent of Ti - 45Al - 2Nb- 0.4Mn and Ti - 45Al- 2Nb at 1350°C was observed to be 0.52 and 0.38, respectively. The difference in the grain growth exponent values has been attributed to the initial grain size and the grain boundary morphology. Interlamellar spacing in the lamellar microstructure, which formed upon furnace cooling from the α phase field, was also observed to increase with increase in annealing time, i.e. interlamellar spacing increased with increase in grain size.

Keywords:

• TITANIUM ALUMINIDE
• GRAIN GROWTH
• INTERLAMELLAR STRUCTURES