Single Crystal Casting
Dr. Peter Müllner
In the 1991 thriller Terminator 2, Arnold Schwarzenegger starring as Terminator T-800 faces off Terminator T-1000. The T-1000 is a liquid-metal robot, which can take on any arbitrary shape. Though the T-1000 may remain science fiction, shaping metals exist and are known as shape memory alloys. In the Magnetic Materials Laboratory, we synthesize and characterize magnetic shape-memory alloy Ni-Mn-Ga. We develop a processing method to create Ni-Mn-Ga with superior purity and homogeneity to enhance its performance. This new method consists of melting Ni-Mn-Ga in a crucible using a 3.5 kW induction furnace, then casting the molten material into a heated alumina mold. The mold contains an oriented seed crystal interfaced with a custom-built, water-cooled copper base system. Following casting, the resulting ingots were polished to remove surface stress. We then performed chemical analysis to reveal the chemical composition and etched the surface to reveal the microstructure. Optical images for the cross-section area of the etched surface showed elongated grains with an average length of 10 mm indicating directional solidification. The energy dispersive spectroscopy data showed minimal segregation along the solidification direction. The large grains, directional solidification, and minimal chemical segregation, are successful steps towards growing segregation-free single crystals.
Mustafa, Ali W.; Johnston, Brent; Eyer, Dillon J.; Condor, Gianella; Munoz, Hailee; and Müllner, Peter, "Single Crystal Casting" (2020). 2020 Undergraduate Research Showcase. 128.