Tensile properties of tempered chromium steels in the temperature range 0°to 700°C

Steels containing 0.2 pet C and 0 to 12 pct Cr have been tempered for different times or recrystallized at 700°C and subsequently tensile tested at 100°C temperature intervals in the range 0° to 700°C. At all temperatures, the strength of the as-tempered steels depends primarily on the dislocation structure inherited from the martensite transformation and work softening observed during deformation at 600° and 700° is attributable to recovery of this structure. Strain enhanced precipitation of M₃C is observed after deformation at 200° to 600°C in all the steels, independent of the nature of the carbide present after tempering. Serrated yielding occurs at temperatures increasing from 200° to 400°C with increasing chromium content and is associated with an increase in strength and strain-hardening rate in all cases. It is concluded that dynamic strain-aging results from dislocation locking by chromium-interstitial complexes in the alloy steels. T. Mukherjee, formerly Research Student, Department of Metallurgy, University of Sheffield, Sheffield England. This paper is based upon a thesis submitted by T. Mukherjee in partial fulfillment of the requirements of the degree of Doctor of Philosophy at the University of Sheffield.