Utilization of a Low-gravity Environment to Fabricate Uniformly Composite Spheres From Imiscible Alloy Systems
Uniform microstructures can evolve during solidification of monotectic composition alloys if the liquid reaction product (L2) wets the primary solid (S1). However, highly segregated macrostructures tend to develop during processing of hypermonotectic alloys. Here the interfacial surface tension can not accommodate the excess L2 which then, because of Earth's gravity, runs down and hangs off the solid as is demonstrated by melting silverfoil (L2) over a suspended nickel sphere (S1). A 1-D numerical solidification model was developed to track heat flow and solidification of the bi-material drop configuration. Experimental processing parameters dictated by the model were utilized to promote and insure a uniform silver thickness on precast nickel spherers within the limited microgravity time provided by the 105 meters of the MSFC Drop Tube Facility.
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Curator: Tom Rathz/UAH tom.rathz@msfc.nasa.gov
Principal Investigator: R.N. Grugel/USRA richard.grugel@msfc.nasa.gov; L.N. Brush/UofWash brush@u.washington.edu