Control of hysteretic properties in powder alloys based on the Fe–Cr–Co system

Abstract

Hysteresis alloys based on the Fe–Cr–Co system are of scientific and practical interest, primarily due to their high manufacturability, high level and temperature stability of magnetic properties, which provide the required hysteresis magnet performance including residual magnetic induction, coercive force, and loop squareness ratio. The research was aimed to control and stabilize the Fe–Cr–Co ridge alloy magnetic properties using reageing. The 22Kh15K4MS hard magnetic powder alloy was investigated after quenching and multistage aging. Billets were obtained by cold pressing at a pressure of 600 MPa and subsequent sintering in vacuum. The samples obtained by sintering in the α phase in the presence of the liquid phase formed during contact melting had a porosity of up to 1 %. The concentration heterogeneity of chromium and cobalt distribution was 0.06–0.08. The alloy magnetic structure parameters were determined by electron microscopy. The relationship between the magnetic structure formation kinetics during aging and the level of magnetic properties was established. After aging, the fine structure of the 22Kh15K4MS alloy was represented by elongated α1 phase sections in the α2 phase matrix. The average particle sizes of the α1 phase were »124 nm in length and »44 nm in width after the first stage of aging, and they remained the same after final aging. It was shown that it is possible to control magnetic properties by reaging without repeated quenching. A slight change in the size and morphology of magnetic phase particles was observed during aging. The influence of the number of reaging cycles on the stability of magnetic properties over time was determined.