Microstructure and Texture Formation during Hot Rolling of Niobium-Rich Gamma TiAl Alloys with Different Carbon Contents

Abstract

Three Gamma-TiAl alloys with a base composition of Ti-45Al-7.5Nb (at. %) and different carbon contents were used for hot rolling experiments. The alloys were powder metallurgically produced and subsequently hot-isostatically pressed. Two hot rolling series with different degrees of reduction during the rolling steps have been performed at temperatures in the upper range of the ( Alpha+Gamma ) phase field. Samples for texture analysis and metallography were taken from various stages of the rolling process as well as after additional annealing. Light-optical and scanning electron microscopy images clearly show the influence of the different carbon contents on the recrystallization behaviour. The rolling texture of the -TiAl phase is dominated by texture components, which indicate mechanical twinning as a predominant deformation mechanism. The hot rolling texture of the -Ti(Al) phase exhibits components similar to those known from titanium based alloys as well as components probably resulting from co-deformation with the Gamma-TiAl phase.