Evaluation of Embrittlement in Isochronal Aged Fe-Cr Alloys by Magnetic Hysteresis Loop Technique

Fe-Cr alloys with different Cr contents were prepared by an arc melting technique. The alloys were isochronally aged in the range from $400^{\circ}C$ to $900^{\circ}C$ with $50^{\circ}C$ steps with a holding time of 100 hours. The ageing produced embrittlement in the alloys due to either the formation of a Cr-rich ${\alpha} phase or a $\sigma$ phase at high temperatures. Magnetic Hysteresis Loop (MHL) and Micro-Vickers hardness were measured at each step to correlate the magnetic and mechanical properties. Coercivity and hardness of the alloys were increased and remanence decreased up to 500-$550^{\circ}C$ due to formation of a Cr-rich ${\alpha} phase. Beyond 500-$550^{\circ}C$ range, the coercivity and hardness decreased and remanence increased due to the coarsening or dissolution of the Cr-rich ${\alpha} phase. In the Fe-48% Cr alloy, formation of the $\sigma$ phase at $700^{\circ}C$ reduced the maximum induction of the alloy significantly.