Alloy Behavior and Design Across Length-Scales: An SMD Symposium Honoring Easo George: Perspectives and Behavior at Extremes
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Michael Mills, Ohio State University; George Pharr, Texas A&M University; Robert Ritchie, University of California, Berkeley; Muralidharan Govindarajan, Oak Ridge National Laboratory
Monday 8:30 AM
March 20, 2023
Room: Cobalt 502B
Location: Hilton
Session Chair: Michael Mills, The Ohio State University
8:30 AM Introductory Comments
8:40 AM Invited
Physical Metallurgy and Mechanical Properties of Iridium and Platinum Alloys Used in Power and Heat Sources Onboard Interplanetary Spacecraft: Easo George1; 1Oak Ridge National Laboratory
Iridium alloys are used to clad the plutonia fuel used in radioisotope thermoelectric generators that provide electric power onboard interplanetary spacecraft. Platinum alloys are used to clad smaller pellets of plutonia whose decay heat is used to keep the electronics of spacecraft from freezing in deep space. Both these alloys have the face-centered cubic crystal structure but exhibit distinctly different mechanical properties, especially at high strain rates. I will review what we have learned over the years about the effects of grain size, temperature, trace elements (good, bad, and indifferent) on their tensile/fracture properties over a wide range of strain rates spanning six orders of magnitude (10E-3 to 10E3 per second). The underlying mechanisms responsible for these effects will be discussed and interesting directions for future research pointed out.
9:10 AM Invited
Easo George - Recollections of His Youth: David Pope1; 1University of Pennsylvania
At times like this it is always informative to ask the following sort of question: When Easo was a newly arrived MSE graduate student at the University of Pennsylvania way back then, was It obvious to us faculty that he would eventually attain his present status in our field? During this talk I will describe his intellectual (and, yes, his physical) characteristics back in those days and attempt to answer that question, (but not necessarily with a totally straight face). I will do this by reviewing two clear examples from his many significant publications to show how he has chosen his projects and how he thinks about them, and then finally, I will discuss the special characteristics that, in my opinion, make him the superbly productive, charming, and supportive colleague that we all know him to be.
9:40 AM Invited
From Superplasticity in Steels to the Great Pyramid of Giza: Jeffrey Wadsworth1; 1former CEO, Battelle
Developments in Aluminum and Titanium alloys for commercial applications of superplasticity in the 1960’s and 70’s created a race to develop the property in steels. It was demonstrated that superplasticity could indeed be developed in steels, but the compositions required ultrahigh carbon (UHC) contents of 1-2%C. This discovery led to the reinvention of techniques to create the ancient Damascus Steel patterns, as well as those of layered or welded Damascus Steel structures. Subsequently, a mystery surrounding the remarkable properties of famous knives created by Frank Richtig at the turn of the last century was solved. Related work led to a comprehensive program of carbon dating in ancient steels, including the discovery that in some cases rust samples as well as solid samples could be dated. A well-documented discovery of an iron plate discovered in the Great Pyramid of Gaza, and the author’s attempt to carbon date it, will be described.
10:10 AM Break
10:30 AM Invited
Future Prospects of MoSiBTiC Alloys as Ultra-High Temperature Materials: Kyosuke Yoshimi1; 1Tohoku University
MoSiBTiC alloys have great potential as ultrahigh temperature materials. However, the high-temperature strength, room-temperature fracture toughness, and oxidation resistance of MoSiBTiC alloys have a trade-off relationship with each other, so there is a need to establish an appropriate balance between these material properties and to further improve their performance. The most important issue to be addressed in the future is microstructure control. Additive manufacturing may be one of the most promising methods. The rapidly solidified MoSiBTiC alloys simulating the effect of rapid solidification by additive manufacturing have microstructures that are one order of magnitude finer than those produced by the conventional arc melting method and exhibit good oxidation resistance at temperatures exceeding 1000ºC. The development of new melting and casting processes for ultrahigh temperature materials would be important in the future.
11:00 AM Invited
Challenges in the Design of Refractory Multi-principal Element Alloys: Carolina Frey1; Leah Mills1; Sebastian Kube1; Tresa Pollock1; 1University of California, Santa Barbara
Refractory Multi-principal element alloys show promise for high temperature structural applications beyond 1200˚C. High levels of alloying can mitigate some of the features that challenge conventional refractory alloys, including limited low temperature ductility, but the compositional search space is large. Challenges in processing, control of phase equilibria and mechanical properties will be discussed using HfNbTaTiZr as a model system. Compositional design requires control of intermediate temperature transformations from bcc and hcp and interstitial element stabilized phases. The role of high throughput processing and machine learning in augmenting the search will be discussed. High temperature properties will likely be enhanced by precipitate strengthening and the possibility of high thermal stability B2 phases will be addressed.