Simultaneous Synthesis and Consolidation of Amorphous Alloys

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

TECHNICAL: Amorphous alloys often exhibit unusual and attractive combinations of physical and mechanical properties. Their usefulness, especially in structural applications, has been very limited due to the difficulty in producing them in bulk form. This program seeks to address this inherent problem of forming bulk amorphous structures. Multilayer thin film structures comprised of the elements constituents of certain binary alloy systems are known to amorphize during annealing due to an inherent thermodynamic driving force in the system. The project combines this solid-state amorphous synthesis with a consolidation process by hot isostatic pressing (HIP) rather than doing either independently, which has been the normal practice to date. Elemental powders of Ni and Ti will be processed using mechanical alloying (MA). The lamella structure of the milled Ni-Ti alloy powder mimics the multilayer thin film structure of the elements of the alloy. Spacing in lamella structure will be optimized for effective amorphization/consolidation as a function of energy input from the mill and milling time. To further understand the cooperative influence of temperature and pressure on the amorphization reaction, an experiment will be developed in which two thin plates of Ni and Ti will be pressed in a uniaxial hot press. This will allow us to study and model the rate of amorphization under simplified conditions, but similar to those in the HIP. One other binary alloy system, namely Ni-Zr, will be studied. The program relies on the fundamental understanding and use of thermodynamics to create a bulk amorphous structure. This may be counter-intuitive, since amorphous alloy processing science generally proceeds via strategies that rely heavily on kinetic considerations. The approach differs from those in traditional studies in that it attempts to combine the synthesis and consolidation of amorphous alloys into a single step, rather than a sequential, series-type approach. The project represents an excellent opportunity to study fundamental aspects of thermodynamics, alloy theory, alloy design, processing science, densification science, metastable structures, and material characterization. NON-TECHNICAL: The success of this program will have a strong impact towards solving the technical difficulties that have mostly prevented the implementation of amorphous alloys in bulk, structural applications. It could, for example, lead to studies on the development of a truly bulk iron base amorphous alloy for use as the core for electromagnets in power generation; such a core has been shown to provide about 60% higher output as compared with the traditional silicon core. Graduate and undergraduate students from Virginia Tech, and one undergraduate student from Morgan State University, will participate in this program. This project will seek to develop a relationship with engineering, physics and chemistry programs at Morgan State University (MSU), one of the Historically Black Colleges and Universities (HBCU's) situated in Baltimore, MD. While MSU has a reputation for sending a large percentage of its graduates from the above programs to top engineering graduate schools in the country, MSE, being a non-traditional engineering program is rarely considered by these students. The outreach program will bring considerable educational and research interactions among faculty and students at both institutions, so as to introduce the students at MSU to career choices and opportunities in materials science. This is expected to lead to some of these students enrolling in MSE programs at Virginia Tech or other engineering institutions. The findings of project will also serve to enhance the subject matter of a powder processing course which the PI teaches to senior undergraduate and graduate students.