In Situ Observation and Phase-Field Simulation Framework of Duplex Stainless-Steel Slab during Solidification

Abstract

The melting and solidification process of S32101 duplex stainless steel (DSS) was investigated using high-temperature confocal microscopy (HTCM). The method of concentric HTCM was employed to study microstructure evolution during the solidification process of S32101 DSS. This method could artificially create a meniscus-shaped solid–liquid interface, which dramatically improved the quality of in situ observations. During the heating stage, γ-austenite transformed to δ-ferrite, and this transformation manifested itself in the form of grain boundaries (GBs) moving. The effects of cooling rate on the solidification pattern and microstructure were revealed in the present research. An enhanced cooling rate led to a finer microstructure, and the solidification pattern changed from cellular to dendritic growth. As the temperature decreased, the commencement and growth of precipitates were observed. In this paper, the experimental data, including parameters such as temperature, cooling rate, and growth mode, were used as the benchmark for the simulation. A simulation framework using Micress linked to a 1D heat transfer model enabling consistent analysis of solidification dynamics in DSS across the whole cast slab was established. Simulating the dendrite growth and elemental segregation of DSS at specific cooling rates shows that this framework can be a powerful tool for solving practical production problems.

Effect of Cooling Rate on Crystallization Behavior during Solidification of Hyper Duplex Stainless Steel S33207: An In Situ Confocal Microscopy Study

“…Additionally, the growth temperature of the δ-ferrite phase (Figure3b) formed at a higher temperature with a slow cooling rate. This tendency was the same as the DTA results (Figure2) as well as the previous work[29], where a higher cooling rate resulted in a higher undercooling degree of melt and a lower crystallization temperature of δ-ferrite. The δ-ferrite grew quickly and a similar merging phenomenon was observed with a temperature decrease.…”

Metallurgical Process Simulation and Optimization

“…The hot deformation characteristics of Ti alloys were analyzed using the strain hardening exponent, strain rate sensitivity, a processing map, and microstructure observation in Piao et al’s study [ 10 ], and an optimum processing temperature and strain rate were proposed. Wang et al [ 11 ] developed an in situ observation method to characterize the solidification of duplex steel during solidification, and phase-field simulation was also carried out to study its solidification and heat transfer behavior. The influence of the mineralogical structure of mold flux film on heat transfer was studied during continuous casting of peritectic steel in the work of Liu et al [ 12 ], which covers the layered structure, crystallization ratio, mineralogical species, and morphology features of flux films.…”