抄録
Steels are characterized by their large quantity, low cost, excellent workability and recyclability. Therefore, they are widely used for automotive and construction components. In manufacturing processes of steels, hot working plays an important role in determining mechanical properties, such as strength and toughness. Therefore, appropriate numerical models are required to understand deformation behaviors and evolution of mechanical properties during hot forming. Among different numerical approaches, Crystal Plastici ty (CP) models have attracted much attention in recent years because CP models can predict macroscopic formability based on microscopic deformation. However, studies on CP modeling of body-centered cubic (BCC) metals, including steels, are fewer compared to those of face-centered cubic (FCC) metals. This is because BCC metals exhibit more complicated deformation than FCC metals due to multiple families of active slip systems, strong temperature and strain-rate dependencies, and non-Schmid effects. Moreover, in high temperature conditions, dislocation recovery is promoted by diffusion of atoms. Therefore, evolution of dislocation density should also be modeled appropriately in CP models. However, some technical problems still remain to develop accurate CP models for high-temperature deformation of BCC metals. In this study, the deformation of SUS430 stainless steel, a typical ferritic stainless steel, was investigated experimentally over a wide temperature range. Moreover, a CP model that describes the deformation behavior of the SUS430 in a wide temperature range was developed. The developed CP model reproduced the temperature dependence of yield stress, whereas it could not predict accurately the work-hardening behavior at high temperatures. Therefore, a new model was introduced to take the temperature-dependent decrease of dislocation density into consideration, improving the prediction accuracy.
