Formation of the first portions of є- and а ' deformationinduced martensite in chromium-nickel steels of the austenitic class

Abstract

Purpose. The first portions of the emerging є- paramagnetic and а '- ferromagnetic martensite under uniaxial compression plastic deformation moderately unstable austenite chromium-nickel X12CrNi15-16 steel experimentally fix. Methodology. Dependence of the magnetic susceptibility of the steel from the degree of deformation K and amount of а '- martensite deformation sensitive magnetometric method is found. This method influence of the magnetization of paramagnetic austenite into account. Neglecting the magnetization of paramagnetic austenite leads to significant errors in determining the very low number of а- phase, for example, the error is more than 1000 % when the content of а -phase 0.005 %, 80 % - at 0.1 %, and only in the presence of 2.5 ... 3.0 % error reaches about 3 %. Findings. In X14CrNi17-18 steel (stable austenite) during plastic deformation by compression (K = 0...67 %) the paramagnetic susceptibility increased by 4 % revealed. In this steel transformation у ^ а ' is not found. In X12CrNi15-16 steel with unstable austenite moderately depending on the degree of deformation three regions of phase transformations found. The first region of deformation: while increasing the plastic deformation (K = 0 ... 26 %) increase in the magnetic state of the austenite у ^ у ' and increase the paramagnetic susceptibility of austenite by 8 % to maximum value z ' / aX takes place. The second region: with increasing deformation (K = 26.5 ... 44 %) in the paramagnetic austenite matrix formed the first portions of the paramagnetic є- and ferromagnetic а ’ martensite deformation (у/тх ^ є + у' + а '). In this region, the amount of deformation occurring а'-martensite Ра = 0.01 ... 0.025 % is found. The third region: with increasing deformation (K = 49 ... 70 %) is transformed paramagnetic phase є and у' to maximum paramagnetic state у 'max austenite (є + у '^ у 'max, у 'max а ' ). Further accumulation of the amount of а -martensite (Ра = 0.03 ... 0.11 %) takes place. Originality. Physical model of the nucleation of the first portions є- and а - martensite deformation is offered. Practical value. The results of research in improving the technology of deformation processing to improve the mechanical and service characteristics of austenitic chromium-nickel steels can be used.