Austenite Formation from Fe-13Ni-1.1C Martensite

Experimental measurements of hardness, optical microstructure, and austenite lattice parameter were carried out on samples cooled to — 196 °C to form martensite and reheated for 1 h at 100 to 1200 °C. Reheating first results in depletion of carbon from the martensitic matrix and in formation of a small amount of austenite and for temperatures above 400 °C it results in secondary hardening presumably due to the formation of low-nickel cementite. Above 600 °C the low-carbon matrix reverses to austenite whose carbon content is determined by the metastable carbon and nickel equilibration of austenite and cementite. Between 700 °C and 800 °C graphite forms and cementite disappears; concurrently the austenite recrystallizes. Above 900 °C the austenite carbon level follows the stable austenite graphite equilibrium. formerly Visiting Professor at Purdue University, is currently Professor of Materials Engineering, Jeonbug National University, Seoul, Korea.