Modelling of isothermal formation of allotriomorphic ferrite transformation at temperatures below the eutectoid in a medium carbon microalloyed steel

The present paper is concerned to the theoretical and experimental descript ion of the isothermal growth kinetics of altotriomorphic ferrite in a mediu m carbon vanadium-titanium microalloyed steel at temperatures below its eut ectoid temperature and above any adiffusional transformation start temperat ure. Since pearlite is formed at these temperatures, the carbon enrichment of austenite far from the alpha/gamma interface remains the same as the ove rall carbon content of the steel, and the soft- impingement effect can be n eglected. Therefore, allotriomorphic ferrite can be considered to grow unde r a parabolic law, and the assumption of a semi-infinite extent austenite w ith constant boundary conditions is suitable for the kinetics of the isothe rmal decomposition of austenite at temperatures below eutectoid and above a ny adiffusional transformation. Moreover, the influence of the austenite gr ain size and isothermal temperature tin the kinetics of the allotriomorphic ferrite transformation has been analyzed.