Abstract
The structure and mechanical properties of two 0.2 wt.% C TRIP-assisted steels (Transformation Induced Plasticity) were compared to evaluate the effect of additional (Cr, Mo, V)-alloying on transformation kinetic and tensile/impact behavior after isothermal bainite transformation (bainitizing) and Q?P (Quenching-and-Partitioning) treatment. The work was performed using SEM, XRD, tensile/impact testing, and computer simulation. It was found that adding 0.55 wt.% Cr, 0.2 wt.% Mo, and 0.11 wt.% V into Mn-Si-Nb steel increased the incubation time in pearlite and bainite temperature ranges by 5.6 and 4.4 times, respectively. More heavily alloyed steel performed an improved combination “Strength/Ductility/Impact Toughness”: its maximum PSE (Product of Strength and Elongation) value of 24 GPa?% referred to bainitizing treatment, whereas the highest KCV_20°Cvalues (220–225 J cm^–2) corresponded to Q?P treatment. Improved mechanical properties of (Cr, Mo, V)-alloyed steel were attributed to a higher amount of retained austenite and a slower rate of TRIP-effect.

Key words
TRIP-assisted steel, bainitizing, Q&P, austenite, mechanical properties

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