Phase State of Fe-Cr-Co Alloys with Aluminum and Niobium Additives.

A study was made of the phase state of alloys of the Fe-Cr- 18% Co system with additions of 1% Al, 1% Nb and 1. 5% Al, 1% Nb. On the basis of an analysis of temperature-concentration sections of the structural diagrams, the boundaries of the alpha - and alpha plus gamma -regions are plotted, and the upper temperature limit of existence of the sigma -phase is determined. It is shown that when aluminum and niobium are introduced into Fe-Cr-Co alloys with 18% Co the alpha -phase region expands to such an extent that in the case of alloys containing 30% Cr there is no longer any need for high-temperature quenching to preserve the single-phase state. A reduction of the quenching temperature from 1300 to 900 degree C has no effect on the level of the magnetic properties of these alloys.