Precipitation Embrittlement Studies in Vacuum Melted Iron-Chromium Alloys

Citation

Wright, William Vale (1955) Precipitation Embrittlement Studies in Vacuum Melted Iron-Chromium Alloys. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/007T-MG19. https://resolver.caltech.edu/CaltechETD:etd-01272004-092755

Abstract

This thesis presents the results of an experimental study on the nature of precipitation embrittlement (475[degrees]C embrittlement) in iron-chromium alloys. Electrical resistance, hardness, tension properties, and microstructure were studied using 19, 25, 34, 42, and 49 per cent chromium-iron vacuum melted alloys. Precipitation embrittlement was found to occur from 450[degrees]C to about 540[degrees]C with the rate of embrittlement increasing with teiriperature. Maximum embrittlement occurs near 500[degrees]C. Increasing the chromium content from 19 to 49 per cent increases the rate and magnitude of precipitation embrittlement. An activation energy of 60,000 cal/mol was established for the process. Precipitation embrittlement was found to be analogous to precipitation hardening in alloys where the formation of a coherent precipitate is responsible for property changes in the alloy. A chromium rich body centered cubic ferrite with slightly larger lattice parameter than the iron rich matrix is proposed as the non-equilibrium coherent precipitate which eventually decomposes to form gross sigma phase.

Thesis Files