Abstract
The secondary hardening behavior of “ausformed” 13 Cr stainless steels was investigated. Steels were deformed by rolling at 450°C or 650°C in the metastable austenite condition prior to martensite transformation and subsequently tempered up to 550°C. Secondary hardening did not appear clearly in the ausformed and tempered specimens when the amount of deformation was increased, while it occurred in the conventionally quenched and tempered specimens at 450°C. By measuring the change in a half-value breadth of X-ray diffraction line with tempering and extracting carbide electrolytically from heat-treated steels, it was assured that this phenomenon could be explained by one of the following two reasons. (1) Precipitation process of carbide was accelerated by plastic deformation of austenite matrix before quenching and precipitation temperature was lowered to a low temperature, then it followed that softening of martensite by tempering would be cancelled by this accelerated precipitation hardening. Or, (2) hardening due to lattice strain produced by plastic deformation was so high that hardening due to precipitation would be covered with it.
Effects of austenitized temperature and deformation temperature on hardening were also studied and discussed.
