Abstract
The influences of aging temperature on the microstructure formation and the mechanical properties were experimentally investigated for the Fe-1.8Cu-15.9Cr-7.3Ni-1.2Mo-0.08Nb-low C, N steel which contained about 10% retained austenite after solution treatment.
The main results obtained are as follows; The hardness change with aging is given from the balance of the precipitation hardening due to ε-Cu phase and the softening due to the formation of reverted austenite. The excellent balances among the strength/ductility and the strength/toughness are obtained for the specimens aged at 813K and 853K for 14.4ks., where the lamella structure consisting of the martensite and the reverted austenite phases are formed. The process of inverse transformation of austenite is mainly controlled by diffusion of Ni-atoms, so that the Ni-atoms are concentrated to the reverted austenite phase in twice of the alloy composition. The ε-Cu precipitates which contributes to the precipitation hardening hardly coarsen even at high temperature, for an instance 10nm in diameter for the specimen aged at 813K for 14.4ks.
