Modelling of Effects of Cold Work on Sigma Phase Growth Rate in Super Duplex Stainless Steel

Abstract

By the modelling of the precipitation and growth behaviour of the sigma phase the quantitative effects of amounts of cold work was investigated in super duplex stainless steels. The cold work promotes sigma phase precipitation. The equation to describe the growth rate of sigma phase proposed formerly by the authors was employed. That is based on the classical nucleation theory and J-M-A-K formula.

The effects of cold work was incorporated in that equation as two parameters. Those parameters were determined using the experimental data. Experimental data was obtained by measuring the growth of sigma phase in the isothermally heated specimen at 1173 and 1223 K. The specimens consisting of 25mass%Cr-mass7%Ni-3mass%Mo-2mass%W-0.3mass%N super duplex stainless steel were prepared with various reduction levels of 3 to 10% in cold rolling process. As result the model to described quantitatively the effect of the amount of cold work on the acceleration of sigma phase was proposed. The validity of the model was confirmed by clarifying to have good fit to the experimental data referred from another work published.