Metallic Glass/Nanocrystal Composites and NiTiHf Shape Memory Alloys for High Temperature Applications
Abstract
Nanocrystalline materials have been subjected to considerable research due to the great potential of improving a number of material properties through grain size refinement such as strength, corrosion resistance, or improved magnetic properties. Various types of nanocrystalline materials can be derived from vapor, liquid and solid states of materials by applying numerous techniques such as sputtering, vapor deposition, rapid solidification, severe plastic deformation, mechanical alloying and devitrification of metallic glass. The latter one has recently taken further interest as an emerging structural materials owing to its impressive mechanical properties. Being promising materials for engineering applications, full application of metallic glasses is limited because of their near zero ductility. The monolithic metallic glasses show high strength and but they tend to deform along one or few very thin shear bands which does not allow for a macroscopic plasticity. Due to the formation of highly localized strain during deformation, metallic glasses fail catastrophically after yielding. Metallic glass/nanocrystal composites on the other hand, have shown improved ductility over the monolithic glass. Partial devitrification of the Al-RE marginal metallic glasses results in anomalous nucleation rate of nanocrystals embedded in amorphous matrix. Despite the volume of the research, an exact explanation for the mechanism underlying the formation of highly populated nanocrystals is still missing. In our previous study, we have investigated the as-quenched structure in details and found that some medium range order (MRO) clustering is responsible for the nanocrystallization of fcc-Al after devitrification.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2021
- Source ID
- FA95502010261
Entities
People
- Eren Kalay
Organizations
- Air Force Office of Scientific Research
- Middle East Technical University
- United States Air Force