A Mechanism of Transition of Austenite to Martensite During Cold Plastic Deformation of Austenitic Steels

Technological processes that involve plastic deformation (bending, rolling, cold stamping, calibration, straightening, rolling of threads) are widely used when manufacturing technological equipment from austenitic steels. Plastic deformation in the cold state leads to an active change in the physical and mechanical properties of the material and affects the load-carrying capacity of structures. The purpose of this study is to qualitatively and quantitatively evaluate the transition of austenite to martensite upon exposure of austenitic steel to cold plastic deformation. The change in the phase composition of austenitic steels by plastic deformation leads to a change in the magnetic properties of the steels, as α-Fe (martensite) has magnetic properties, while γ-Fe (austenite) does not. Non-magnetic austenitic steels become magnetic after the deformation, and the higher the degree of deformation, the stronger the magnetic properties. Thus, in the case of cold plastic deformation of austenitic steels, deformation hardening is observed when two processes occur simultaneously: a dislocation and phase transition from γ-Fe to α-Fe with the formation of deformation martensite. Studies of the mechanism of transition from austenite to martensite during cold plastic deformation were performed using the example of austenitic steel 12X18H10T, depending on the degree of deformation in the range of 0 — 45 %. A magnetometric method was used in the study of this transition. It was established that at the deformation rate of 44.6 %, the amount of martensite in the deformed steel was 45.5 %. This indicates that a complete transition of austenite to martensite was not observed, and the structure in the deformed metal was austenitic-martensitic.

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