Austenitic transformation and influence of prior ferrite formation on martensite transformation characteristics of Al-added P91 ferritic-martensitic steel

•Austenitization and martensite formation kinetics studied in P91-0.5Al steel.•Two stage austenitization: α (within martensite laths) → γ and δ→γ observed.•Isothermal characteristics of γ transformation studied by Dictra® simulations.•Factors dominating martensite transformation changed with temperature.•Effect of ferrite & incomplete α→γ transformation on Ms temperature studied.