Creep of Cr-Ni stainless steels due to stress-induced martensitic transformations

Abstract
Commercial Cr-Ni austenitic stainless steels show an anomalous fall of proof yield strength arid critical stress of microdeformation at temperatures above M_s due to the development of FCC HCP ( ) transformation in elastic range of loading. The martensiteformation under elastic stresses causes low-temperaturc creep, and elongation of specimens is proportional to the amount of the phase. Low-temperature creep at temperatures below oecurs on reverse transformation of stress-induced martensite to austenite as well. High-temperature thermomechanical treatment and aging, on the one hand, suppress the low-temperature creep, and on the other hand, intensify the anomalous fail of yield strength at temperatures above M_s and move the start of this fall to higher temperatures. Key factors responsible for this effect are the decrease of martensite formation rate, expansion of elastic region due to strengthening of austenite, and rise of maltensitic points as a result of phase precipitation.