Simulation of Precipitation Kinetics and Precipitation Strengthening of B2-precipitates in Martensitic PH 13-8 Mo Steel

The strength of quenched Co-free martensitic PH 13-8 Mo steel increases significantly during isothermal ageing at 575 degrees C due to precipitation of nanometer-sized particles. The evolution of these ordered B2 type precipitates is simulated by thermo-kinetic calculations and compared with experimental results. The composition of the B2-nuclei is determined from minimization of the critical nucleation free energy. The results of the simulations are utilized for the assessment of contributions of different strengthening mechanisms to the total lower yield strength evolution. We observe good qualitative agreement between the simulations and the experimental data.