Response and prediction of microstructures indicating deceleration growth condition in a Sn-Ni peritectic alloy

Abstract

The Sn-36 at.%Ni peritectic alloy in which both the primary and peritectic phases are intermetallic compounds was directionally solidified attending different deceleration growth conditions. The cellular-dendrite growth of the primary Ni3Sn2 phase was studied in this analysis, and the influence of the deceleration rate on the microstructure length scales including primary/higher order dendrite arm spacing (λ1, λ2, λ3) and dendrite tip radius (R) were analyzed. Experimental results showed that although these length scales all decreased with the increasing deceleration rate, the responses of the secondary dendrite arm spacing λ2 and the tip radius of primary dendrite R are faster than that of λ1. This difference in response leads to a larger variation in the λ1/λ2 ratio with the increasing deceleration rates, as compared with the λ2/R ratio. Furthermore, the ratio of the thickness of primary dendrite stem d to the primary dendrite arm spacing λ1, d/λ1 was used to predict the melt concentration at the solid/liquid interface Cl. These length scales were related to the melt concentration Cl which is obtained through the d/λ1 ratio.