Abstract
The migration of the primary/peritectic interface in local isothermal condition is observed in dendritic structure of Sn–Ni peritectic alloy after experiencing interrupted directional solidification. It was observed that this migration of primary Ni3Sn2/peritectic Ni3Sn4 interface towards the primary Ni3Sn2 phase was accompanied by migration of liquid film located at this interface. The migration velocity of this interface was confirmed to be much faster than that of peritectic transformation, so this migration was mostly caused by superheating of primary Ni3Sn2 phase below TP, leading to nucleation and migration of liquid film at this interface. This migration can be classified as a kind of liquid film migration (LFM), and the migration velocity at the horizontal direction has been confirmed to be much faster than that along the direction of temperature gradient. Analytical prediction has shown that the migration of liquid film could be divided into two stages depending on whether primary phase exists below TP. If the isothermal annealing time is not long enough, both the liquid film and the primary/peritectic interface migrate towards the primary phase until the superheated primary phase has all been dissolved. Then, this migration process towards higher temperature is controlled by temperature gradient zone melting (TGZM).
Highlights
Nucleation of liquid films in the interior of the solid grains has been found in directional melting experiments which have been carried out in some alloys[14,15,16]
To investigate and characterize the position and morphology of primary/peritectic interface in local isothermal condition, the interrupted directional solidification in which the isothermal condition is realized through a stationary standing of the samples after downward directional solidification has been carried out
The migration of primary/peritectic interface has been analyzed in a Sn–Ni peritectic alloy through interrupted directional solidification
Summary
Nucleation of liquid films in the interior of the solid grains has been found in directional melting experiments which have been carried out in some alloys[14,15,16]. The nucleation and migration of the liquid films can lead to the change in both the position and morphology of the primary/peritectic interface where the liquid films located. The aim of this study is to shed light on the stability and variation of primary/peritectic interface of a peritectic system in local isothermal condition For this reason, the Sn-Ni peritectic system in which both the primary Ni3Sn2 phase and peritectic Ni3Sn4 phase are intermetallic compounds with narrow solubility ranges has been selected. Based on the experimental observations on the microstructure, especially the variation in both position and morphology of the primary/peritectic interface, analytical models have been established to describe the migration process of liquid film and primary/peritectic interface in isothermal condition in this peritectic system
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