Evolution of Transient Nature Nanoscale Softening During Martensite Tempering

In this study, the progression of martensite tempering as a function of tempering parameter has been investigated using instrumented nanoindentation. Three distinct stages of tempering related to the carbon segregation, carbide nucleation, and Ostwald ripening were identified. During the second tempering stage, the nanohardness achieves a plateau which is attributed to the change of carbide morphology, dissolution of intra-lath carbides, and growth of inter-lath and block boundary carbides.