Abstract

JUNIOR, A. M. J  and  BALANCIN, O. MICROSTRUCTURAL ANALYSIS OF THE ACTIVE SOFTENING PROCESS IN A FERRITIC STAINLESS STEEL DEFORMED AT HIGH TEMPERATURES. Rev. LatinAm. Met. Mat. [online]. 2002, vol.22, n.1, pp.3-7. ISSN 0255-6952.

A ferritic stainless steel, with a chromium/nickel equivalent ratio of 7.4, was deformed in torsion over a temperature range of 900°C to 1200°C and a strain rate of 1 s-1. The flow curves attained showed two different shapes: at higher temperatures, the materials typically softened only by dynamic recovery while, at lower temperatures, the flow curves were characterized by a rapid rise to a peak stress, followed by extensive flow softening. There was a very significant reduction of grain size during deformation under all the conditions studied, suggesting that dynamic recrystallization occurred. These observations are incongruent with the literature, which reports that the restoration mechanisms for ferrite change from dynamic recrystallization to dynamic recovery when the deformation temperature decreases, at a constant strain rate. Observations of the microstructural evolution after interrupting the tests at different levels of strain and analysis of the dependence of the work-hardening rate on the applied stress lead to a discussion about the competition between recovery and recrystallization during deformation of ferritic stainless steel at high temperatures and upon extensive strain.

Keywords : dynamic recovery; dynamic recrystallization; continuous dynamic recrystallization.