Effect of deformation temperature on the structural parameters, phase composition and microhardness of Fe-28Mn-2.7Al-1.3C steel single crystals processed by high-pressure torsion

E. Melnikov, E. Astafurova, G. Maier
Received: 19 January 2018; Revised: 18 February 2018; Accepted: 02 March 2018
This paper is written in Russian
Citation: E. Melnikov, E. Astafurova, G. Maier. Effect of deformation temperature on the structural parameters, phase composition and microhardness of Fe-28Mn-2.7Al-1.3C steel single crystals processed by high-pressure torsion. Letters on Materials, 2018, 8(2) 178-183
BibTex   DOI: 10.22226/2410-3535-2018-2-178-183

Abstract

Using X-ray diffraction method, the effect of cold (23°C) and warm (200, 400 ºC) high-pressure torsion (HPT, 6GPa, N=1,3,5 full revolutions) on the structural parameters and phase composition of single crystals of high-manganese austenitic steel Fe-28Mn-2.7Al-1.3С (wt. %) was investigated. Regardless of the deformation temperature and the number of revolutions under HPT, steel retains an austenitic structure with high lattice parameter of 3.638-3.653Å; the microhardness of the steel increases, and its magnitude and radial-distribution substantially depends on the HPT temperature.Using X-ray diffraction method, the effect of cold (23°C) and warm (200, 400ºC) high-pressure torsion (HPT, 6GPa, N=1, 3, 5 full revolutions) on the structural parameters and phase composition of single crystals of high-manganese austenitic steel Fe-28Mn-2.7Al-1.3С (wt. %) was investigated. HPT leads to the formation of a misoriented austenitic structure with predominant orientation of {111}-planes in the plane of the anvils. Increase in strain (the number of revolutions) contributes to a decrease in sizes of the coherent scattering regions and microstrain of the crystal lattice and causes an increase in the concentration of stacking faults calculated on the basis of the strain-induced shifting of X-ray lines. Regardless of the deformation temperature and the number of revolutions under HPT, steel retains an austenitic structure with lattice parameter of 3.638-3.653Å. An increase in deformation temperature contributes to a decrease in the austenite crystal lattice parameter that indicates on a partial decarburization of austenite, but only austenite lines are observed on X-ray diffraction patterns. As a result of deformation, the microhardness of the steel increases, and its magnitude significantly depends on the HPT temperature. In the case of cold deformation by HPT, the distribution of microhardness along the diameter of the disk is quasi-homogeneous and varies slightly with increasing number of revolutions. An increase in the deformation temperature is accompanied by the appearance of inhomogeneity in the distribution of the microhardness along the diameter of the disk – the values at the center are lower than that at the periphery.

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