Effects of Cu addition on the synergistic effects of Ti–B in thermomechanically processed low carbon steels

The present study concerns the influence of Cu addition on the synergistic effects of Ti–B in low carbon thermomechanically processed steels. Effective retardation of the γ → α transformation due to the combined addition of Ti and B is known to enhance the hardenability of a wide range of low carbon microalloyed steel. On the other hand, addition of Cu in low carbon age hardenable steel suppresses the pearlitic transformation resulting into a microstructure constituted by interspersed islands of martensite in ferritic matrix. Therefore, it may be of interest to examine the role of Cu on the synergistic contribution of Ti and B in respect of increasing hardenability of austenite. In the present study, effects due to the addition of Ti, B and Cu in different steels are interpreted in respect of microstructure–property correlation. It is demonstrated that the addition of 1.5 wt% Cu perceptibly enhances the synergistic effect as manifested by lowering the transformation temperature of austenite. Addition of 0.8 wt% Ni in Cu–Ti–B steel does not alter the transformation temperature of austenite to any appreciable extent. However, Cu–Ni–Ti–B steel has resulted into the enhancement of strength–ductility combination.