Influence of Heat Treatment on the Structure, Phase Composition and Properties of Deformable Hard-Magnetic Fe–30Cr–20Co–2Mo Powder Alloy

Abstract

The structure, phase composition, mechanical and magnetic properties of deformable hard magnetic Fe–30Cr–20Co–2Mo alloy obtained by sintering (1400°C, 240 min) of elemental powder compacts. The effect of quenching (1300°C, water) and stepwise heat treatment on the structure, mechanical properties during compression and magnetic characteristics of the samples is established. In the samples after sintering, a high proportion of the brittle sigma phase is recorded (~47%). The yield strength of such samples under compression is 1330 MPa with a brittle nature of fracture. After quenching, the yield strength decreases to 607 MPa, but the ductility of the samples increases. The increase in the samples ductility after quenching is associated with the fixation of the ferrite phase in the structure with a small amount of chromium oxides. After stepwise heat treatment, the ductility remains close to the ductility of quenched samples, but the yield strength increases to 1190 MPa. The Portevin–Le Chatelier effect is observed on such samples. Structural changes in the alloy during stepwise heat treatment lead to the appearance of technically suitable magnetic properties (residual induction 0.83 T, coercive force 56.4 kA/m, magnetic product 16 kJ/m³).