J. Phys. IV France
Volume 112, October 2003
Page(s) 433 - 436

J. Phys. IV France
112 (2003) 433
DOI: 10.1051/jp4:2003918

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

Yu.N. Goykhenberg

Southern Ural State University, Pr. Lenina 76, Chelyabinsk 454080, Russia

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

© EDP Sciences 2003