Phase Selection in a Laser Surface Melted Zr-Cu-Ni-Al-Nb Alloy
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IT has been shown that significant improvements in properties can be achieved by processing materials under non-equilibrium conditions in both the liquid and solid states.[1–3] The demand for materials that are stronger, capable of use at much higher temperatures, more corrosion resistant, and much less resource expensive than those currently used has grown significantly over the past few decades. Several new processing technologies have been developed during the past few decades including rapid solidification, spray forming, mechanical alloying, ion mixing, vapor deposition, laser processing, and plasma processing. In addition, the emergence of additive manufacturing (AM) as a competitive alternative to more traditional manufacturing techniques[4] in terms of cost, speed, reliability, and accuracy has increased the need for greater understanding and control of non-equilibrium processing.[5–7] The application of AM technology to the fabrication of components with novel structures that are both multifunctional and high performance is therefore of particular interest at present. The highly non-equilibrium
BRIAN A. WELK, Research Engineer, HAMISH L. FRASER, Ohio Regents Eminent Scholar and Professor, and VIKAS DIXIT, Post Doctoral Researcher, are with the Center for the Accelerated Maturation of Materials, Department of Materials Science & Engineering, The Ohio State University, 2041 College Road, Columbus, OH 43210. Contact e-mail: [email protected] TIM WILLIAMS, Transmission Electron Microscope Manager, is with the Monash Centre for Electron Microscopy (MCEM), Monash University, Clayton, VIC 3800, Australia. MARK A. GIBSON, Senior Principal Research Scientist, is with the CSIRO Process Science & Engineering, Clayton, VIC 3168, Australia. Manuscript submitted January 28, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
nature of AM favors the formation of bulk materials with unique microstructures and properties.[8] It provides a beneficial method to develop new materials such as nanophase (both crystalline or quasicrystalline), amorphous, functionally gradient, and porous materials with properties and functions which do not exist currently. As a result, the development of techniques for the rapid screening of potential alloy systems for their suitability for non-equilibrium processing is of immediate and immense value. The current investigation is directed toward the use of laser engineered net shaping (LENS) in combination with laser surface melting to evaluate the influence of non-equilibrium processing on the phase selection and microstructure development in potential glass-forming systems. It has been shown that for good glass-forming ability, an alloy melt should have a combination of (1) low entropy and enthalpy, to provide a low thermodynamic driving force for crystallization, and (2) low atomic mobility associated with a viscosity that is high and comparatively weakly temperature dependent, which kinetically suppresses crystallization.[9] The Zr-Cu-Ni-Al-Nb system is known to have a moderately good glass-
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