Undercooling and Wettability Behavior of Interstitial-Free Steel on TiN, Al₂O₃ and MgAl₂O₄ Under Controlled Oxygen Partial Pressure

The heterogeneous undercooling degree of interstitial-free steel (IF steel) on various substrates was measured through observing the recalescence phenomenon by sessile drop method at the oxygen partial pressure of 10⁻²³ atm, where there was no obvious interaction between the steel and the substrate. The wetting behavior of liquid IF steel against different substrates was also studied during the sessile drop test. The results suggested that the undercooling degree increased with the increase of cooling rate, and the effective contact surface area between the liquid steel and the solid substrate could not fully explain the undercooling behavior of the designed cases as there is no interaction layer. Furthermore, a method to calculate the critical contact angle for IF steel against its substrate was developed in this study, which could be adapted to explain the undercooling variance of IF steel with the change of its substrate. The undercooling degree increased with the increase of the critical contact angle, and the critical contact angle was also improved with the increase of lattice disregistry.