Properties of stainless Cr-Mn steels with a difference in the stability of austenite during deformation

Abstract

1. Stainless steels containing 14% Cr, 0.15% N, and 14\2-22% Mn, which are austenitic with cooling to \t-253\dg, undergo the martensitic transformation during deformation, with formation of \ga\t" and \ge\t" phases. The addition of 3% Ni to the steel with 18% Mn suppresses the martensitic transformation, and the steel remains austenitic with deformation at temperatures down to −253°. 2. The mechanical properties of the steel are determined by the phase formed in the course of plastic deformation. Raising the manganese concentration reduces the tendency for strain martensite to be formed at +20\dg, reducing the ultimate strength and increasing the ductility. Due to the weaker martensitic transformation at \t-196\dg than at +20\dg, the variation of the ultimate strength with the manganese concentration is characteristic of that for substitutional solid solutions. 3. The toughness and type of fracture at low temperatures depend to a considerable extent on the stability of austenite during deformation. Brittle sections in the fractures of austenitic steel indicate the presence of bcc or hcp phases. With increasing stability of the austenite the fracture changes from brittle to mixed. Austenitic steels resistant to the γ»α″ and γ»e″ transformations undergo ductile fracture. 4. The addition of 3\2-5% Ni to the steel with 18% Mn greatly increases the ductility and toughness at low temperatures.