Previous studies have disclosed that, under the influence of elastic andrnplastic strains at the temperature below the point corresponding to thernbeginning of strain-induced martensite formation (M_d), a number ofrnmetastable austenitic steels and alloys undergo phase transformations of γrn→ α′ , γ → ε or γ → ε → α′ type. The transformations result in thernformation of stress-assisted or strain-induced martensite. Strain-inducedrnmartensite significantly affects the properties of steels: it improves thernintensity of strain hardening, reinforces the uniform elongation capacity ofrnthe material and, under conditions of cooling the metal below M_d, it mayrnlead to unusual increase in elongation, which is referred to as therntransformation plasticity effect [1]. The presence of ferromagnetic α′ -rnmartensite even in the amount as low as 3-5% significantly reduces operatingrnproperties of metastable steels and alloys, e.g. corrosion resistance andrnmagnetic permeability rate, thus a number of steels can no longer be used asrnparamagnetic materials in structures with high magnetic protection. Asrndistinct from Fe-Ni-based alloys, the metastable steels and alloys based onrnFe-Mn and Fe-Mn-Cr have not been so far examined in the course of loadingrnwithin elastic deformation and plastic deformation areas. All the availablerndata concerning the α′ -strain-induced martensite content measurements werernobtained by means of a Shteinberg-Zyuzin magnetometer with the measurementrnerror within ± 1% on unloaded tensile test pieces, which had been strainedrnto a certain degree, starting from 5%. The presence of the α′ -phase can bernexplicitly determined by means of the X-ray diffraction analysis, but thernuncertainty in the determination is of the order of 5%.
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