Abhi Roop Reddy Tokala, “The Effect of Cerium and Cooling Rates on the Cast Microstructure of Aluminum-Cerium Alloys – Wedge Mold and Melt Spun Castings”
Mentor: Pradeep Rohatgi, Materials Science
Poster #209

Combining aluminum with cerium creates easy-to-cast Al-Ce alloys that exhibit improved high-temperature performance, overcoming their limitation in mechanical strength at elevated temperatures. A series of nine Al-Ce alloys of compositions ranging from 2 – 18 wt% Ce were cast in steel wedge molds, and the effect of composition on the microstructure was studied. Micrographs revealed two major phases in Al-Ce alloys, including primary α-Al (in hypoeutectic alloys) or primary Al11Ce3 (in hypereutectic alloys) phase and a lamellar eutectic phase (of α-Al and Al11Ce3). The Al-12wt% Ce sample was remelted and recast in a water-cooled copper wedge mold and also melt spun on a copper drum into thin fibers. The cooling rate in the water-cooled copper mold was estimated to be between 5 oC/s and 30 oC/s from the base of the wedge to the top, based on the microstructure obtained in A356 alloy. The secondary dendrite arm spacing (SDAS) and lamellar spacing in the eutectic was characterized as a function of distance from the base of the wedge. The SDAS in copper wedge mold increased from 14.5 µm at 1” to 18.5 µm at 2” from the base of the wedge. The SDAS was 2.6 µm in the melt spun sample.