Linzhong Zhuang

Constitutive Modeling and Activation Energy Maps for a Continuously Cast Hyperperitectic Steel

An appropriate experimental scheme and an accurate constitutive model are the two key factors that determine the success or failure of the constitutive equations used to simulate hot deformation behavior during the continuous casting process. In this study, according to the characteristics of the thin-slab continuous casting process, the experimental scheme on hot tensile tests is designed and validated by the analysis of fracture surfaces. Isothermal hot tensile tests were performed on a Gleeble 1500 thermomechanical simulator at four different temperatures (1173xa0K, 1273xa0K, 1373xa0K, and 1473xa0K) and four different strain rates (10−3, 10−2, 10−1, and 1 s−1). Based on the flow stress obtained from the tensile tests, the Arrhenius-type constitutive equation was established. It is shown that the simulation results are in good agreement with the experimental data. To further understand the constitutive behavior, activation energy maps were also developed in this study. Through a brief analysis of the activation energy map, directions for future work were surmised.

Experimental and Theoretical Studies of the Hot Tearing Behavior of Al-xZn-2Mg-2Cu Alloys

The effect of Zn addition on the hot tearing susceptibilities of non-refined Al-xZn-2Mg-2Cu (xxa0=xa02-12xa0wtxa0pct) alloys was investigated via direct crack observations and load response measurements. The obtained experimental results were compared with the predictions made using a modified Rappaz–Drezet–Gremaud (RDG) hot tearing model. Both the minimum crack width and load at the non-equilibrium solidus (NES) temperature (which served as a good indicator of hot tearing response) were observed at a Zn concentration of approximately 4xa0wtxa0pct, and the formation of cracks was highly correlated with the predictions made via the modified RDG hot tearing model (although the obtained relationship critically depended on the magnitude of fraction solid at which solid coalescence was expected to occur). Furthermore, it was confirmed from the load development pattern that the addition of Zn into the matrix of Al-xZn-2Mg-2Cu alloys promoted the formation of coalesced networks, which decreased their corresponding coalescence fraction solids.