Isothermal transformation diagrams for alloyed ductile cast iron

Abstract

Isothermal transformation (IT) diagrams which were determined metallographically are presented for a ductile cast iron alloyed with manganese, molybdenum, and copper, following austenitisation at 870 and 920°C. Isothermal transformations were conducted over the temperature range 275–650°C for times between 0·5 and 120 min. The IT diagrams displayed a nose at ~650 and 425°C for the pearlite and upper bainite reactions respectively. The diagrams could be separated into two overlapping diagrams corresponding to transformations in the eutectic cell and intercellular regions. When compared with previous data for an unalloyed iron, the alloying additions were found to delay the transformation, and to a greater extent above 450°C than below this temperature. Increasing the austenitising temperature was observed to delay the transformation. The effect of a 50 K increase was equivalent to increasing the total alloy content in the eutectic cell area by about 0·4 wt-% in this alloy.

MST/2040