Effect of retained austenite on austenite memory of a 13% Cr–5% Ni martensitic steel

► In situ observation showed microstructure evolution from martensite to austenite. ► Austenite memory occurred by using pre-existing retained austenite as a substrate. ► Reversed austenite acts as a sink for carbon in retained austenite containing steel. ► Tempered martensite decomposed in fully martensitic steel, avoided austenite memory. ► (Cr, Mo)23(C, N)6 precipitates could increase nucleation sites for globular austenite. The effect of retained austenite on the microstructure evolution from martensite to austenite in relation to austenite memory of a 13% Cr–5% Ni martensitic steel was studied. In situ observations by confocal laser scanning microscope suggested that austenite memory occurred during the reverse transformation from martensite (α) to austenite (γ) in the presence of retained austenite, but was absent in a fully martensitic sample. The microstructure evolution during intercritical tempering treatment in the α+γ two phase region indicated that, reversed austenite formed in the retained austenite containing steel by using the pre-existing retained austenite as a substrate; it also bore the Kurdjumov–Sachs (K–S) orientation relationship with the martensite matrix and was stabilized by Ni enrichment. For the fully martensitic sample, a certain amount of martensite re-transformed to austenite while the rest transformed to tempered martensite; the tempered martensite then decomposed to ferrite with (Cr, Mo)23(C, N)6 precipitates. Austenite memory was absent due to the decomposition of the tempered martensite in the austenization process. Effect of the retained austenite on the reversion process from martensite to austenite was discussed in detail. A mechanism by which the retained austenite affected austenite memory was proposed.