Effect of retained austenite on the microstructure and mechanical properties of martensitic precipitation hardening stainless steel

The effect of retained austenite () on the microstructure and mechanical properties of a martensitic precipitation hardening stainless steel was experimentally investigated, whose chemical composition was Fe-1.8Cu-15.9Cr-7.3Ni-1.2Mo-0.08Nb-low C, N (mass%). The microstructures of all specimens consist of a typical lath martensite with interlath films of the retained , which is not reverted with aging. Cu-rich precipitates which may contribute to precipitation hardening can not clearly be observed. The tensile properties and Charpy absorbed energy are linearly approximated to the amount of retained as follows: 0.2% Y.S. (MPa) = 1192.3 – 13.6 × %, T.S. (MPa) = 1250.1 – 9.3 × %, El. (%) = 12.16 + 0.43 × %, R.A. (%) = 64.25 + 0.14 × %, and A.E. (J) = 72.5 + 0.8 × %. The introduction of retained is not beneficial to the fatigue limit. An excellent combinations of strength, ductility and toughness obtained in the present work is attributed to the introduction of retained and also to the chemical composition of the specimen used.