Microstructure Evolution by Thermomechanical Processing in the Fe-10Al-12V Superalloy

Abstract

Nowadays, great efforts are being made to develop bcc-superalloys for medium- and high-temperature applications. However, the high brittle-to-ductile transition temperatures (BDTT) have restricted their application. Therefore, designing hot-processing routes to obtain a refined grain in these new superalloys is required. Particularly in the Fe-10Al-12V (at%) alloy, we have recently tested the BDTT shifting and, using physical models, it was indicated that a combination of L21-precipitate sizes with small grain sizes could shift the BDTT below room temperature. Here, we will present the study that allowed us to design the processing route for grain refinement in the tested superalloy. Molds of different geometry and with metallic and sand walls were used to test two different types of casting. Carbide conditioning treatments for improving the sizes and distribution were studied. The recrystallization process was explored first by hot rolling and post-annealing in stepped geometry samples with two different columnar grain orientations. Finally, we analyzed the grain microstructure obtained along a hot processing route consisting of carbide conditioning treatment, forging into a squared bar, and hot rolling up to a 2.8 mm thickness strip.