Low-temperature sintering and hot rolling of hard powder magnetic Fe-Cr-Co alloy

A.S. Ustyuhin1, A.B. Ankudinov1, V.A. Zelenskii1, I.M. Milyaev1, M.I. Alymov1,2
1A.A. Baikov Institute of Metallurgy and Materials Science RAS, Leninskiy pr. 49, 119334 Moscow
2Institute of Structural Macrokinetics and Materials Science RAS, Academician Osipyan str., 8, 142432 Chernogolovka

Abstract

In present work a method for obtaining technically useful Fe-26%Cr-16%Co-2%Mo-2%W hard magnetic alloy from powder raw materials is proposed. The distinctive feature of the method is the lowered sintering temperature of powder compacts (1100 - 1200 °C).In present work a method for obtaining technically useful Fe-26 %Cr-16 %Co-2 %Mo-2 %W hard magnetic alloy from powder raw materials is proposed. The distinctive feature of the method is the lowered sintering temperature of powder compacts (1100 – 1200°C). Sintered blanks are subjected to a hot rolling process at 1150°С. Magnetic material produced by the proposed method has relative density about 97 – 98 %. Magnetic properties of alloy sintered at 1200°C (Br = 1,2 T, Hcb = 51kA / m, (BH)max = 30 kJ / m3) are on the same level as for alloys obtained by powder metallurgy methods with sintering temperatures higher than 1300°C and their cast analogs. At the same time low magnetic properties were obtained on alloy sintered at 1100°C with the following hot rolling. Using EDX analysis and X-ray phase analysis it is established that this is due to the presence of significant fraction of non-magnetic γ-phase in the samples. Apparently under these sintering conditions the redistribution of alloy components does not succeed. Tensile strength tests of the hot-rolled alloy after heat treatment showed a significant effect of sintering temperature on the samples strength. The tensile strength was higher for the samples sintered at 1100°C (700 – 930 MPa) as compared to the samples sintered at 1200°C (520 – 590 MPa). Investigation of the samples microstructure showed that alloy sintered at 1200°C has a more coarse-grained structure. Apparently this is a cause of the tensile strength reduction.

Received: 25 May 2017   Revised: 16 June 2017   Accepted: 27 June 2017

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