STABILIZATION OF PRECIPITATED AUSTENITE IN TEMPERED FE-MN-C STEELS

Concepts of austenite stabilization in low carbon, low manganese steels via heterogeneous precipitation to produce compositional control of the austenite are discussed. A detailed thermodynamic analysis has been made of heterogeneous austenite formation in a microstructure consisting of tempered ferrite and dispersed manganese-rich cementite. A common basis has been defined for comparison of the energetics of two modes of austenite formation: (1) heterogeneous nucleation at a ferrite-cementite interface and subsequent growth into either ferrite or cementite and (2) heterogeneous precipitation on ferrite grain boundaries. A reduction in the manganese content of cementite below its equilibrium value was found to favor austenite nucleation at ferrite-cementite interfaces and the subsequent conversion of the cementite into austenite. Experimental verification of these results is also discussed. © 1990.