In-situ observation of S/L interface migration and mechanical property increase of Inconel 600 alloy prepared by electromagnetic levitation

The Inconel 600 alloy was highly undercooled and its S/L interface migration during recalescence was observed in real time by using the electromagnetic levitation (EML) system. The characteristic of S/L interface migration and the dendritic growth velocity are strongly dependent on undercooling. At a small undercooling, the γ phase nucleates and grows to the undercooled melt with a sharp interface, and the corresponding microstructure appears as dendrite with strong texture. Nevertheless, once the undercooling exceeds the critical undercooling the sharp S/L interface transforms to a planar shape, which is attributed to the formation of equiaxed grain with a diffused orientation distribution. The 60°<111> annealing twins are generated only when the undercooling is larger than 130 K, due to the obvious recrystallization and sufficient driving force. Besides, the compressive tests were performed on the bulk Inconel 600 alloy samples. The results demonstrate that the elastic modulus is affected little by the undercooling, however, the yield strength obviously increases with the enhancement of undercooling. The strengthening mechanism is mainly ascribed to the formation of sub grain boundaries and annealing twins.