Insight on creep behavior for arrayed interphase nano-precipitation in Ti-Microalloyed HSLA steel

Abstract

The creep properties of Ti-microalloyed steel with numerous interphase precipitated TiC were investigated in the medium-high temperature range. Interestingly, in comparison with the as-received steel without heat treatment, the heat-treated Ti-microalloyed steel possessed a better creep property, primarily due to the numerous carbides with a regular array morphology. Furthermore, the experiment results indicated that the creep deformation was primarily dominated by dislocation glide and climb mechanisms, due to its activation energy of 348 kJ/mol and higher apparent stress exponent. In addition, the dislocation morphology at different creep temperatures also exhibited distinct interaction behaviors between interphase precipitated carbides and dislocations. For instance, longer dislocations with entanglement morphology within the ferrite matrix indicated that dislocation climb occurred during creep deformation above 425 °C, which can be ascribed to the coarsening of TiC. On the other hand, for creep deformation at low temperature, i.e. ≤ 425 °C, the short dislocation profile implied strong interaction between carbides and dislocations, which was associated with the large inhibition ability of the tiny-sized carbides. Moreover, finite element analysis was used to identify various strain field distributions, i.e., butterfly-shaped strain-chain, skew-shaped, and twisted-shaped, which were analyzed according to the angle between the loading axis and the regular array of carbides.