Prediction of the concentration inhomogeneity of powder magnetic hard alloys based on the Fe-Cr-Co-Mo system and the effect of Sm additions on their magnetic properties

Abstract

Hysteresis alloys based on Fe-Cr-Co system are extensively used in the instrument-making industry as a material for synchronous motors of navigation systems, in the electronic industry, and other mechanical engineering fields. The following requirements are imposed on Fe-Cr-Co alloys: temperature stability of magnetic characteristics over time, manufacturability, low porosity and concentration inhomogeneity, which allow to obtain high-quality magnetic and mechanical properties. Materials based on conventional alloying systems, such as Fe-Cr-Co, have outlived themselves. An urgent line of the development of new materials and improvement of the properties of existing ones is alloying with rare-earth metals. The effect produced by Sm addition on powder analogs of Fe-Cr-Co system remains unstudied. In this paper, 22Kh15K4MS powder magnetic hard alloy alloyed with samarium in an amount of 0.5 wt. % was studied. The billets were obtained by cold pressing at a pressure of 600 MPa followed by vacuum sintering. The concentration inhomogeneity of Cr, Co, Mo, Sm was determined after 12 different sintering modes. A model of diffusion homogenization of ridge alloys, which allows to numerically evaluate the effect of sintering modes on the concentration inhomogeneity, was plotted. The distributions of chromium, cobalt, and molybdenum correspond to the asymptotically logarithmically normal law. Samarium is unevenly distributed in the structure. The effect of samarium additions on the magnetic properties of the alloy has been demonstrated. The alloying of 22Kh15K4MS alloy with 0.5 wt. % of samarium allows to obtain powder hysteresis magnets with a coercive force in the range from 3.9 to 33.0 kA/m and a residual magnetic induction from 0.44 to 0.95 T.