Low-temperature transformation to bainite in a medium-carbon steel

Abstract

Abstract The consequences of reducing the carbon concentration from 0.8 to 0.6 wt.% in a bulk nanostructured bainitic-steel have been investigated with the aim of enabling processing. We observed that the average thickness of the product phase plates increased from below 20–40 nm to about 100 nm after isothermal transformation at the same temperature. The increase in plate size led to decrease in hardness as expected. However the hardness reduction was not as large as might be expected, a transition to lower bainite at temperatures below 250°C may have provided additional strengthening. Transformation just below the martensite start temperature resulted in a mixture of martensite and bainite, with no observed increase in the rate of bainite transformation.