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Possessing unique thermomechanical properties, the discovery of nickel-titanium shape memory alloys (SMAs) has sprouted a plethora of applications in various fields, including aerospace, automotive, microelectronics, and medical devices. Due to its excellent biocompatibility and its ability to mimic biological forces, the medical implant industry has shown strong interest in expanding the application of NiTi SMAs. However, traditional SMA functional properties are limited by a single set of thermomechanical characteristics in a monolithic component. Past efforts in overcoming this limitation have had little success until recently with the invention of the multiple memory material (MMM) processing technology. This novel processing technology enables multiple functional responses through the augmentation of local microstructure and composition using a high power density source such as a laser. This thesis presents an investigation of the effect of laser processing on pseudoelastic behaviour and corrosion response of medical grade SMAs.

Shape Memory Alloys (SMAs) are advanced materials with interesting properties such as pseudoelasticity (PE) and the shape memory effect (SME). Recently, the CoNiGa system has emerged as the basis for very promising High Temperature Shape Memory Alloys (HTSMAs), with possible applications in the aerospace and automotive industries. Although the CoNiGa system shows significant promise for its use as HTSMAs, limited studies are available on them. Hence, a more intensive investigation of these alloys is necessary to understand their phase stability over a wide range of temperature and compositions in order for further development of CoNiGabased HTSMAs and future use of the model in alloy design. This formed the basis of motivation for the present work. In this work, a thermodynamic model of the ternary system is calculated based on the CALPHAD approach, to investigate the thermodynamic properties, phase stability and shape memory properties of these alloys. The CALPHAD approach is a computational method that enables the calculations of thermodynamic properties of systems. This method uses all available experimental and theoretical data in order to calculate the Gibbs energies of the phases in the system. The software used to carry out the calculations is "ThermoCalc," which is a computational software using CALPHAD principles, based on the minimization of Gibbs energy, and is enhanced by a global minimization technique on the system. The stability of the beta phase at high temperatures was enforced accurately by remodeling the CoGa system. The binary CoGa system that makes up the ternary was remodeled, as the beta phase (which is very important as it dominates the central region of the ternary CoNiGa system where the shape memory effect is observed), re-stabilizes as the temperature increases above the liquidus in the CoGa system. Phase relations and thermodynamic properties of the CoNiGa system based on all experimental information were evaluated. Different properties like enthalpies, activities, sublattice site fraction of vacancies and phase fractions calculated in the system matched well compared to the experimental information used to model the system. Also, the phase equilibria among the gamma (fcc), beta, gamma'(Ni3Ga), delta (Ni5Ga3) and epsilon (Ni13Ga9) were determined at various temperatures.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available in print.

Thesis (M.S.)--Universiity of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science in Mechanical Engineering." "A thesis entitled"--at head of title. Bibliography: leaves 131-145.

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Kenneth Gall; Committee Member: David Bucknall; Committee Member: Karl Jacob.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (MS)--Montana State University--Bozeman, 2010. / Typescript. Chairperson, Graduate Committee: David A. Miller. Includes bibliographical references (leaves 69-73).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 124-127).