Phase and structural transformations in corrosion-resistant steels upon high-pressure torsion and heating

Abstract

High-pressure torsion (HPT) at a pressure of 6 GPa and room temperature is found to form a nanocrystalline structure in corrosion-resistant austenitic 05Kh15N9D2TAMF and 08Kh18N10T steels and a submicrocrystalline structure in corrosion-resistant ferritic 08Kh18T1 steel and armco iron. X-ray diffraction analysis of both austenitic steels reveals the γ → α and γ→ ɛ→ α martensitic transformations during HPT at room temperature. After HPT, the strain hardening in the austenitic and ferritic steels is approximately the same and mainly determined by nano- and submicrocrystalline structures, and the role of alloying and phase composition weakens. The thermal stability of the hardening in the austenitic and ferritic steels is almost the same, ∼400°C. As a result of HPT, the austenitic 08Kh18N10T and ferritic 08Kh18T1 steels acquire an axial texture with the predominant 〈211〉γ direction in austenite and the 〈110〉α and 〈311〉α directions in martensite and ferrite, respectively. The axial texture is retained in both steels up to a heating temperature of 750°C.