LAUSR

This paper reports the results of investigation on 0.1C-17Mn-5.5Ni-1.8Al-2.7W-4.6Mo-2.3Cu-0.002B steel designed to assume excellent combination of strength and toughness. The air induction melted steel was subjected to hot forging at 1200 °C followed by hot rolling in six passes from 1100 °C. The rolled samples were reheat-quenched from 1050 °C in iced water. The quenched samples were isochronally aged at temperatures within 500-650 °C at interval of 50 °C. The mechanical properties were determined by hardness measurement and tensile testing. Structural characterization was accomplished by x-ray diffraction, optical and electron microscopy. Differential scanning calorimetric study was conducted to understand the precipitation kinetics. A typical age-hardening behavior was noted in the aged samples due to the precipitation of M 2 C and Ni 3 Al. Strain hardening of martensite, precipitation hardening due to the presence of nanosized precipitates and Orowan hardening were found to be instrumental in attaining a maximum hardness of 723 HV. The microstructure of aged samples consists of retained austenite, ε -martensite, α ′-martensite and uniformly distributed nanosized precipitates of Ni 3 Al and M 2 C, lying broadly within two different size regimes. The sample peak aged at 550 °C attained a strength of 1.4 GPa at a total elongation value of 25%. The combination of high strength and high ductility has resulted from precipitation strengthening, TRIP phenomenon and high degree of structural fineness.