The JHP Research Group
As a result of our efforts in the analysis and modeling of alloy solidification it has been possible to identify new microstructural morphologies and to establish processing conditions where nucleation controlled kinetics dominates the microstructural evolution. This basic information can be applied to understand grain refinement and novel microstructures in cast and rapidly solidified alloys. It also is used to guide microgravity materials processing and alloy design including the solidification processing of composite materials. Extreme solidification conditions at high rates and /or high undercooling often result in metastable phases and amorphous alloys. Our work on amorphous Al alloys has focused on understanding glass formation and the primary crystallization reaction that yields a high density of Al nanocrystals. Interestingly, similar microstructures can be synthesized by the repeated cold rolling of elemental multilayers as a driven system processing where the deformation induced alloying at interfaces is a key issue for study.
Our work has yielded new understanding on the nucleation of phases during interdiffusion and interface reaction in thin-film multilayers. With this understanding we have developed the concept of a kinetic bias and have demonstrated the application of biasing to control diffusion pathways and produce phase selection during interfacial reactions in multicomponent systems. These concepts provide for an effective strategy to synthesize structural composites by in-situ reactions and also to develop electronic materials such as photovoltaics or high-temperature devices from multilayers. We have recently extended the capability of using in-situ reactions and kinetic biasing to the design of robust coatings that exhibit self-healing behavior as well as oxidation protection at high temperature.
Other studies of multiphase microstructures involve examining high-temperature alloys such as superalloys, titanium aluminide intermetallics and refractory alloys. The examination of phase stability and reaction kinetics during processing provides a basis for the achievement of tailored microstructures and alloy designs to enhance performance in structural applications as demonstrated in advanced Mo-Si-B alloys.
Contact
Professor John H. Perepezko
University of Wisconsin – Madison
1121 Engineering Research Building
1500 Engineering Drive
Madison, WI 53706
Phone: (608) 263-1678
Main Phone: (608) 263-1660
Fax: (608) 262-8353