Solidification mechanism of austenitic stainless steels solidified with primary ferrite

The solidification mechanism of austenitic stainless steels solidified with primary ferrite is clarified in terms of crystallography. The formation of austenite was expected to take place by the peritectic/eutectic reaction in the interdendritic region of the primary ferrite, but no unique orientation relationship was confirmed between the primary ferrite and the austenite. The austenite was found to keep growing along its <100> direction, independently of the primary ferrite, even after the primary ferrite changed its growth direction. This was confirmed by solidification experiments with changing heat flow directions, and was supported by the observation that the austenite forms crystallographic domains different from those of the primary ferrite in the final microstructure. Thus, it is concluded that the austenite is not crystallographically restricted by the primary ferrite, and that the growth of the primary ferrite and that of the austenite are crystallographically independent of each other.

Austenite at the dendrite boundaries of the preceding ferrite is not crystallographically restricted by the primary ferrite, and that the growth of the primary ferrite and that of the austenite are crystallographically independent of each other.183