Structure formation, phase transformations and properties in Cr–Ni austenitic steel after equal-channel angular pressing and heating

Abstract

It is shown that cold equal-channel angular pressing (ECAP) of corrosion resistant austenitic 0.07%C–17.3%Cr–9.2%Ni–0.7%Ti steel leads to formation of submicrocrystalline structure: generally oriented subgrains and cells with separated grains (100–250 nm in size). The steel samples 20 mm in diameter and 80 mm in length were subjected to ECAP at room temperature for four passes. The angle between the channels was 120°. ECAP promotes the martensitic transformation which becomes more active only after four passes, leading to the formation of 45% martensite. During heating, the fraction of high-angle boundaries and the volume of austenite are increased, and the microstructure becomes more equiaxed. Submicrocrystalline structure with grain size 150–250 nm and 80% of austenite was obtained upon heating to 550 °C. Such structure exhibits a substantial strain hardening (yield strength 1090 MPa relative to the initial with 320 MPa) and an elongation of 12%.