Mater.Phys.Mech.(MPM)
No 2, Vol. 40, 2018, pages 201-211

COMPARISON OF INFLUENCE FORGING AND EXTRUSION ON
MICROSTRUCTURE OF HEUSLER ALLOYS

I.I. Musabirov, I.M. Safarov, R.M. Galeyev, D.R. Abdullina, R.Y. Gaifullin,
D.D. Afonichev, V.V. Koledov, R.R. Mulyukov

Abstract

The results of investigation of the microstructure of two polycrystalline Ni-Mn-Ga alloys subjected to thermo-mechanical treatment by multiple isothermal forging and extrusion are presented. Alloy forging at a temperature of 680úC and 700úC leads to the formation of a bimodal structure which has large grains of several hundred micrometers surrounded by a layer of the fine-grained structure. As the result of the further treatment by extrusion at 710úC the volume fraction of the fine-grained structure is increased. At the same time, anisotropy of thermal expansion during the martensitic transformation is observed in the alloys in both states due to residual tensile stresses introduced in the last stages of treatment. The performed investigation shows high potential of the thermo-mechanical treatment for obtaining structurally modified Heusler alloys having a sufficient level of functional and service properties for practical applications.

Keywords: Heusler alloys, martensitic transformation, thermo-mechanical treatment, multiple isothermal forging, extrusion, EBSD, texture, anisotropy

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