Investigation on morphology evolution of secondary branch during peritectic solidification in a temperature gradient through morphology characteristic: Experimental measurement and prediction

Abstract

Despite the obvious influence of the secondary branch on final microstructure and properties of alloy, investigation on the morphology variation of it during solidification is not enough. On the basis of a parameter ϕ, the morphology evolution of it during peritectic solidification was analyzed. Experimental measurements on two peritectic alloys: Sn–Ni and Sn–Mn show that ϕ first decreases then turns to increase with solidification time. The minimum of ϕ during peritectic solidification is found after peritectic reaction. Further examination shows that ϕ first decrease because it is mainly determined by the growth of secondary branch before peritectic reaction. Then, it is mainly dependent on the radius of secondary branches since the growth space for them is obviously restricted after peritectic reaction. Further analysis shows that the continuous increase of ϕ with solidification time after peritectic reaction is caused by the remelting/resolidification process by both the Gibbs-Thomson (G-T) and temperature gradient zone melting (TGZM) effects on secondary branch. It was also confirmed that the remelting/resolidification process by the G-T effect is less important as compared with that by the TGZM effect. As a result, resolidification on both the front and back edges of thicker secondary branches leads to the “V”-type variation of ϕ during peritectic solidification. The analytical prediction in which the influences of these effects are taken into account shows reasonably agreement with the experimental measurement.