Effects of Ti/Mo and Ti/Cu ratio on precipitation behavior of Ti-bearing steel: findings from experiments and critical patent analysis

Abstract

A dual phase structure consisting of ferrite and martensite has been achieved in Ti-bearing steels microalloyed with Mo or Cu, respectively, which were treated under different austenitizing and hot deformation conditions to investigate the effects of second microalloying elements and thermomechanical processes on the microstructural evolution and mechanical properties. The results showed the largest microhardness values, 343 HV0.1 for Ti–Mo steel and 307 HV0.1 for Ti–Cu steel, in microalloyed steels austenitized at 1200 °C with 30% deformation strain. Furthermore, critical patent analysis revealed that higher tensile strength is achieved in a Ti–Mo steel having a larger Ti/Mo atomic ratio, but no such relationship between tensile strength and Ti/Cu atomic ratio applies to Ti–Cu steel. This finding can be ascribed to the different metallurgical effects of Mo and Cu in the Ti-bearing steels. For example, the addition of Mo in a Ti-bearing steel leads to tiny carbides due to the decrease in coarsening via the synergistic effect of Ti and Mo. On the other hand, the separate precipitation of TiC and Cu in the Ti-bearing steels is consistent with the results of patent analysis. That is, the tensile strength of these steels is not associated with the Ti/Cu atomic ratio.

Keywords

• Ti-bearing steel
• Microhardness
• Transmission electron microscopy
• Ti/Mo
• Ti/Cu
• Patent