Structural-and-Phase Transformations in Fe-4.10 and 7.25 at.% Mn Alloys under Intensity External Actions

Abstract

The effect of high-pressure torsion (HPT) (P = 8 GPa, e = 5.9) and irradiation with continuous beams of Ar+ ions with energy E = 15 keV on the atomic structure and phase composition of initially quenched iron alloys with 4.10 and 7.25 at.% Mn was studied by the method of Mössbauer spectroscopy. The supersaturated α-solid solution of Fe-7.25 at.% Mn, in contrast to the stable Fe-4.10 at.% Mn, which passes into a highly nonequilibrium metastable state as a result of HPT deformation, is transformed under the influence of ion irradiation at an abnormally low temperature of 280 °C into a two-phase α + γ-state with a highly enriched γ-phase (austenite) (38.4 at.% Mn) and a depleted α-solid solution with 5.76 at.% Mn. The rapid processes with the formation of the γ-phase with a concentration of Mn close to the extrapolation estimate using the equilibrium phase diagram are explained by the cascade radiation shaking of the material by post-cascade powerful elastic and shock waves. Cascade radiation shaking plays the role of temperature and opens up the possibility of achieving states close to equilibrium in the absence of thermally activated processes at record low temperatures.

Keywords

• Fe-Mn alloy
• ion irradiation
• austenite formation
• severe plastic deformation
• high-pressure torsion
• long-range effects