Liquid Ni-31.7%Sn-2.5%Ge alloy was highly undercooled by up to 238 K (0.17T L ) with glass fluxing and drop tube techniques. The dendritic growth velocity of primary Ni 3 Sn compound shows a power-law relation to undercooling and achieves a maximum velocity of 380 mm/s. The addition of Ge reduces its growth velocity as compared with the binary Ni 75 Sn 25 alloy. A structural transition from coarse dendrites into equiaxed grains occurs once undercooling exceeds a critical value of about 125 K, which is accompanied by both grain refinement and solute trapping. The Ni 3 Sn intermetallic compound behaves like a normal solid solution phase showing nonfaceted growth during rapid solidification. Intermetallic compounds have developed into an important category of structural materials with potential high temperature applications. Since their microstructural morphology and solute distribution are intrinsically correlated with mechanical properties, extensive work has been done on the directional and rapid solidification processes of intermetallic alloy [1][2][3][4][5][6]. However, most previous investigations were concentrated on the microstructural evolution at small undercooling condition. If an intermetallic compound nucleates and grows from a highly undercooled alloy melt, its formation mechanism will display novel kinetic characteristics because of the extremely nonequilibrium thermodynamic state. During conventional solidification, the heterogeneous nucleation caused by the crucible or mold walls prevents liquid alloys from achieving large undercoolings. Fortunately, glass fluxing [5] method and drop tube processing [1] provide an effective way to eliminate heterogeneous nuclei and subsequently undercool liquid alloys to a great extent. The Ni 3 Sn intermetallic compound has attracted much attention in research because it shows an anomalous increase in yield stress with rising temperature like the Ni 3 Al alloy [2,[7][8][9]. The Ni 3 Sn intermetallic compound has a cubic BiF 3 -type(DO 3 ) crystalline structure above 1193.5 K and transforms into an ordered hexagonal Mg 3 Cd-type (DO 19 ) structure at lower temperatures. Meanwhile, Ni 3 Snbased alloys usually exhibit satisfactory undercoolability to realize bulk rapid solidification. The objective of this paper is to investigate the dendritic growth mechanism and solute trapping effect of the Ni 3 Sn intermetallic compound during the rapid solidification of the highly undercooled ternary Ni-Sn-Ge alloy. Both glass fluxing and drop tube techniques have been applied to achieve high undercoolings.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.