Abstract
Aging behaviors of both isothermal and continuous heating of maraging stainless steels containing cobalt and molybdenum were investigated by resistivity measurements at liquid nitrogen temperature. The resistivity change during aging, which is in good agreement with that of the specific heat previously measured by the authors, may be due to the appearance and redissolution of the solute rich-zones. In addition, these behaviors are scarcely affected by the presence of molybdenum, which is considered to be a hardening element. Isothermal resistivity decreases rapidly in the earliest stage of the rich-zone formation. After this stage there is a much slower reaction which proceeds over a period of time corresponding to the precipitation hardening stage. The reversion curve experimentally obtained can be considered as a resultant combination of two component curves: one giving an initial increase in resistivity due to the true reversion, and the other of decreasing resistivity due to the rich-zone formation of solute remaining in the solid solution even after the preaging treatment. Only in the earliest stage, the low-temperature aging is steadily suppressed by cold work prior to aging.
