Low temperature bainite in steel with 0.26 wt% C

Low temperature bainite has been produced in steel with 0.26 wt% C. In this steel the bainite transformation was suppressed, firstly, by adding substitutional solute of about 2 wt% Ni and, secondly, by modifying the conventional single-step bainite transformation. This modification made use of the suppression of martensite start of the undecomposed austenite due to carbon partitioning between that austenite and the formed bainitic ferrite. Consequently, it has been experimentally proved that generations of bainite were formed at temperatures lower than the martensite start of the bulk alloy. Dilatometric measurements were used to design and monitor the bainitic transformation process. The structure was characterized using light optical microscopy, scanning electron microscopy and X-ray diffractometry. In order to investigate the effect of the microstructure parameters on the material's mechanical properties, compression tests have been conducted at room temperature. The results were compared to those obtained by bainitic transformation in single-step process.

Research highlights▶ Low temperature bainite is produced in 0.26 wt% C steel. ▶ Alloy and process design enable decreasing the carbon content of the alloy. ▶ Generations of bainite are formed at temperatures lower than MS of the bulk alloy. ▶ Bainite plate thicknesses record values between 90 nm and 164 nm. ▶ Y.S. up to 1570 MPa and U.S. up to 2200 MPa are recorded in compression.