It is well known that the ordering of atoms at the nanoscale dictates the properties and performance of materials, but knowledge of the quantitative relationships among properties, performance and structure - in particular the short-range ordering of atoms - is lacking for many structural alloys. Knowledge of these relationships has the potential to enable new high-strength, corrosion-resistant materials for use in transportation, energy, and infrastructure applications. This Designing Materials to Revolutionize and Engineer our Future (DMREF) award supports research to develop an improved fundamental understanding of short-range ordering, in order to identify guidelines for the design of new metallic materials with superior properties. Alloys with short-range order have characteristics of hard, but brittle intermetallics in the short-range, but also of soft pure metal or solid solutions, in the medium- to long-range. Despite classical understanding that suggests otherwise, there is increasing evidence that shows that short-range ordering can lead to unexpected improvements in mechanical properties. A short-range order-assisted alloy design concept will be explored as a new route to overcome the fundamental strength-toughness limitations in physical metallurgy. The overall goal of this research is to establish the fundamental understanding and the generic design rules that enable effective utilization of short-range order to realize damage-resistance in extreme environments. Concepts from this research are incorporated into educational modules in place at local science museums, and further educational benefits will stem from this work through the active participation of student researchers.
This work aims to unravel what controls short-range order stabilities and characteristics, understand fundamentals of short-range order-assisted deformation micro/nano-mechanics, and design novel complex concentrated alloys that overcome current strength and toughness limits. It is necessary to understand how specific aspects of short-range order chemistry, size, and strength can be controlled, and how such variations would influence the interaction with dislocations. To this end, one of the most important challenges is regarding characterization. The typical size of the short-range ordered zones reaches the resolution limits of the conventional microscopy and diffraction tools such as the transmission electron microscopy, the atom probe tomography, and the x-ray diffraction. The research team will employ a novel, multi-pronged approach, combining theoretical modeling (ab-initio density functional theory calculation, Monte-Carlo simulation, and molecular dynamics), metallurgical processing (fabrication & testing), and atomically-resolved advanced structural characterization techniques (resonant x-ray scattering, in-situ scanning electron microscopy, and revolving scanning transmission electron microscopy) in order to overcome this challenge, and to link atomic-scale short-range order-characteristics to engineering properties at the macro-scale.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
