**Aarne Pohjonen \*, Mahesh Somani and David Porter**

Materials and Production Technology Department, University of Oulu, 90014 Oulu, Finland; Mahesh.Somani@Oulu.fi (M.S.); David.Porter@Oulu.fi (D.P.)

**\*** Correspondence: Aarne.Pohjonen@Oulu.fi; Tel.: +358-40-771-9225

Received: 5 June 2018; Accepted: 10 July 2018; Published: 12 July 2018

**Abstract:** We present a computational method for calculating the phase transformation start for arbitrary cooling paths and for different steel compositions after thermomechanical treatments. We apply the method to quantitatively estimate how much austenite deformation and how many different alloying elements affect the transformation start at different temperatures. The calculations are done for recrystallized steel as well as strain hardened steel, and the results are compared. The method is parameterized using continuous cooling transformation (CCT) data as an input, and it can be easily adapted for different thermomechanical treatments when corresponding CCT data is available. The analysis can also be used to obtain estimates for the range of values for parameters in more detailed microstructure models.

**Keywords:** austenite; steel; thermomechanical processing; phase transformation; nucleation; ferrite; CCT; TTT; incubation; transformation start
