PHASE SELECTION OF AISI 304 STAINLESS STEEL DURING DIRECTIONAL SOLIDIFICATION

摘要

Solidification sequence of AISI 304 stainless steel influences the microstructures which determine the mechanical properties and corrosion resistance of the alloy. This paper studies phase/microstructures selection of directionally solidified AISI 304 stainless steel based on the interface response function (IRF) model to predict the primary phase during directional solidification. With the criterion of the highest interface temperature and the IRF model for single phase growth, the interface response functions of δ phase and y phase are calculated. It is found that the competitive growth between the stable phase (δ) and metastable phase (γ) exists during solidification process due to different solidification conditions. For the AISI 304 stainless steel calculated, metastable phase (γ) dendrites begin to precipitate as a primary phase when the growth rate is greater than 4.2cm/s at a given temperature gradient (G) of 400K/rnm. The influence of temperature gradient on the critical growth rate (Vc) from planar to cellular and the interface temperatures in the directionally solidified AISI 304 stainless steel is analyzed as well.