On melt concentration at the solid/liquid interface during preparation of directionally solidified Sn–36 at.%Ni peritectic alloy

Experiments consisting of melting followed by thermal stabilization ranging from 0 to 6 h on Sn–36 at.%Ni peritectic alloy have been carried out in Bridgman-type furnace. Both primary Ni3Sn2 and peritectic Ni3Sn4 phases are intermetallic phases with narrow solubility in this peritectic alloy. A mushy zone is formed between the complete liquid zone and the non-molten zone due to imposed temperature gradient. The transport of atoms due to this temperature gradient cause extensive variations in both microstructure and melt concentration at the solid/liquid interface. Microstructure evolution and solute concentration field in the liquid at the mushy zone/liquid interface have been characterized. An analytical model is proposed to describe the melt concentration at the mushy zone/liquid interface in peritectic alloys during thermal stabilization. When both the remelting of primary α phase and solubilities of primary and peritectic phases are taken into consideration, the calculations show reasonable agreement with experimental results.