PAMS Seminar: "High-throughput Investigations of Phase Formation and Mechanical Properties in Complex Metallic Alloys" by Dr. Katharine Flores

Dr. Katharine Flores
Department of Mechanical Engineering & Materials Science
Institute of Materials Science and Engineering
Washington University in St. Louis

Abstract:

Meeting the design requirements of the next generation of high performance transportation systems, power generators, and energy storage devices requires the discovery and development of new structural alloys with enhanced properties. In this work, we integrate computational simulations and high-throughput synthesis methods to rapidly screen and identify alloy compositions with desirable structure-property combinations. The first part of this presentation will focus on the application of this methodology to the discovery of metallic glass-forming alloys. Using molecular dynamics simulations, we investigate the evolution of the atomic structure from the liquid to room temperature for more than 200 alloy compositions in a range of binary and ternary systems. These results are then compared with glass-forming compositional regimes identified experimentally in alloy libraries produced by a high-throughput laser-deposition technique. The simulated and experimental glass forming compositional ranges are found to be in excellent agreement. Based on this comparison, we then identify structural parameters in the simulated liquid that are predictive of glass formation upon quenching. To further demonstrate the utility of the high-throughput synthesis method, we next apply it to investigate “high entropy” alloys. Compositional and microstructural libraries of an AlxCoCrFeNi high entropy alloy are constructed over a wide composition range. As the Al content increased from x = 0.15-1.32, the crystal structure was observed to transition from FCC to BCC/B2, in excellent agreement with previously published work. In addition to the presence of the expected phases, the laser-processed microstructure was surprisingly consistent with that produced by casting. In light of this, the laser processing conditions were then varied in an effort to study the sensitivity of the microstructure and properties to heating and cooling rates. These results are compared with existing models for dendritic solidification.

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