Effects of Alloying Element on Supercooled A3 Transformation

The cooling rate dependence of A3 transformation and maximum supercooled A3 temperatures have been investigated on eleven kinds of iron binary alloys by using a rapid cooling apparatus. Maximum supercooled A3 temperatures of Fe-Mn alloys show good agreement at higher manganese concentrations with those reported previously but are displaced to lower temperatures at lower manganese concentrations. Extraporation of the resulting data into zero content of the alloying element leads to the maximum supercooled A3 temperature of about 720°C for pure iron. The maximum supercooled A3 temperatures of Fe-Cr, Fe-Cu and Fe-Mo alloys descend with increasing content of each alloying element and those of Fe-Al, Fe-Ti and Fe-V alloys ascend. In Fe-Co alloys, their maximum supercooled A3 temperature ascend up to about 40%Co and are then lowered. Si, W and Nb have little effects on the maximum supercooled A3 temperature of iron. Some of the alloying elements have a different effect on the change of A3 transformation temperature of iron with concentrations in the non-equilibrium condition and in the equilibrium condition.