Accelerated discovery and development of high temperature structural alloys

Michael S. Titus

Assistant Professor of Materials Engineering

Purdue University

Researchers and engineers constantly seek out new materials systems that increase the operating temperatures of critical components in turbine engines, rocket nozzles, and other flight structures. This talk will focus on two classes of materials: refractory-based complex concentrated alloys and new γ’-strengthened Co-based superalloys, for which we employ high-throughput thermodynamic calculations and high-throughput first-principles calculations, respectively, to rapidly evaluate phase equilibria.

Complex concentrated alloys (CCAs, also known as high entropy alloys) are non-dilute alloys with no base element – for example MovNbxTayWz. This type of alloy represents an infinite composition space for researchers to explore, and this space poses both significant opportunities and dreadful challenges to researchers. To more rapidly discover new alloy compositions, we have employed high-throughput thermodynamic calculations over a large refractory-based composition space. During the first half of this talk, I will present our recent work that has (1) identified new alloy candidates that exhibit moderate densities, good phase stability, and high melting temperatures and (2) determined when CALPHAD-based approaches are suitable for extrapolation into higher-order composition space.

The second half of the talk will focus on our work to strengthen Ni- and Co-based alloys via solute-enhanced coherent interfaces. We have recently identified solute segregation to superlattice intrinsic stacking faults (SISFs) in Co- and CoNi-based superalloys, and we hypothesize that this segregation may be exploited to increase the shearing resistance of γ’ precipitates in superalloys. We use first-principles methods combined with statistical mechanics to calculate the SISF energies, equilibrium SISF compositions, and critical γ’ shearing stresses in Co-based superalloys. I will present our efforts to validate these calculations through high-resolution transmission electron microscopy and atom probe tomography, and new alloying strategies will be discussed.

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SHORT BIO:

Michael joined the School of Materials Engineering at Purdue University as an Assistant Professor in December 2016. Michael completed his B.S. in Engineering (The Ohio State University) in 2010 and Ph.D. in Materials (University of California Santa Barbara) in 2015. From 2015 to 2016 he was an Alexander von Humboldt Postdoctoral Fellow at the Max Planck Institute for Iron Research in Dusseldorf, Germany. Michael’s current research interests include accelerated discovery and development of structural alloys through high-throughput experiments and thermodynamic calculations as well as solute interactions with crystalline defects.