Austenite in transformation-induced plasticity steel subjected to multiple isothermal heat-treatments

Van Tuan Duong, You Young Song, Kyong-Su Park, H. K. D. H. Bhadeshia and Dong Woo Suh

Abstract

The thermodynamic limit to the progress of the bainite reaction in steels containing a cementite-inhibitor, often leaves large quantities of thermally or mechanically unstable austenite. Such austenite is not effective in delaying the onset of plastic instabilities during the course of deformation. In such circumstances, it is useful to conduct isothermal transformation at a high temperature where the rate of reaction is relatively rapid, followed by a lower temperature step that permits more bainite to be generated. This in turn increases the stability of the refined austenite, which then transforms gently over a large range of strain during a tensile test. A significant corollary is that the two-step heat treatments are unnecessary in low-carbon steels, where the bainite reaction is able to proceed to a greater extent before reaching the thermodynamic limit. Furthermore, the two-step process can be counter-productive in low carbon steel, because the austenite content is reduced to a level below which it does not enhance the mechanical properties. Other circumstances in which multiple heat treatments are necessary are also discussed.

Metallurgical and Materials Transactions A, 45 (2014) 4201-4209.

Download paper

Related plates

multiple heat treatements




Related papers





Hydrogen TWIP Nuclear growth Maraging steel Bearings Spheroidisation of superbainite
Duplex steel TRIP multipass welds Bainitic powder Shear instabilities Surface hydrogen
Surface displacements Broken bainite Bearing steel Percolation Mn TRIP
Mixed FSW tools Rolling-sliding wear of superbainite Brittle zones Mathematical modelling



PT Group Home Materials Algorithms