Microstructure and Mechanical Properties of Fe sub 3 Al Alloys With Chromium

• Published in: Journal of materials science 1993-04, Vol.28 (8), p.2040-2048
• Main Authors: Knibloe, J R, Wright, R N, Trybus, C L, Sikka, V K
• Format: Article
• Language: English
• ISSN: 0022-2461

Alloys based on Fe sub 3 Al have an equilibrium DO sub 3 structure at low temperatures and transform to a B2 structure above approx 550 deg C. The influence of different rates of quenching from the B2 region to room temperature and of subsequent heat treatments on the microstructure and mechanical properties of powder metallurgy (P/M) alloys with two different chromium contents have been examined. Optimizing the processing to maximize the amount of B2 order, without eliminating dislocations that enhance both strength and ductility, yields room-temperature ductility approx 20%, although the fracture mode is primarily brittle cleavage. The B2 structure generally has lower flow stress than the DO sub 3 structure because of its lower strain-hardening rate, although B2 order actually has higher yield strength when the structure is free of dislocation. Increasing the Cr content from 2-5% has little effect on ductility, although the 2% Cr alloys generally have higher yield strengths and larger order parameters.