Kinetics and Crystallography of Intragranular Ferrite Formed on MnS+V(C,N) Complex Precipitate in Austenite

摘要

The microstructure of intragranular ferrite transformation in the austenite containing B1-type complex inclusions/precipitates are reviewed. The intragranular ferrite transformation is promoted remarkably with the presence of V(C,N) formed on incoherent MnS inclusions in austenite. Ferrite nucleates preferentially on the austenite/V(C,N) interphase boundaries of such complex precipitates, across which there are irrational and non-specific orientation relationships. Intragranular ferrite is idiomorphic for small undercooling but becomes acicular as the transformation temperature is lowered. The idiomorphic ferrites tend to have low-energy orientation relationships with respect to V(C,N), resulting in irrational and non-specific orientation relationships between the ferrite and austenite. For the acicular ferrite, near Kurdjumov-Sachs orientation relationships are achieved with respect to the austenite. The intragranular ferrite transformation is accelerated significantly in the steel containing the complex precipitates when weak hot rolling is applied to the austenite after the V(C,N) precipitation treatment.