Effect of Cr-Rich Phase Precipitation on Magnetic and Mechanical Properties of Fe-20% Cr Alloy

Magnetic Hysteresis Loop (MHL) and micro-Vickers hardness measurements were carried out in isothermal aged Fe-20 wt. % Cr alloy. The results were compared with the existing atom probe data at similar heat treated conditions. Coercivity and hardness of the alloy was increased and remanence of the alloy was decreased with the increase in ageing time. Such increase in the magnetic and mechanical hardness was due to the nucleation and growth of Cr rich α´ phase. The size of the Cr rich α´ phase precipitates were increased and the number density of the precipitates were decreased with the increase in ageing time observed by atom probe analysis. In this work a good correlation between hardness (H_v) and coercivity (H_c) was found with the combined effect of precipitate size (r) and number density (n). A linear relationship was found with the change in coercivity and hardness of the alloy indicating that the MHL technique would be a good Non-Destructive Evaluation (NDE) tool for the evaluation of thermal embrittlement in structural components made of Fe-Cr alloys.