Dr. Michael Gao (高长华) Senior Research, National Energy Technology Lab Senior Research Associate, Department of Materials Science and Engineering Carnegie Mellon University 时间：2008-7-22 上午10：00 地点：暨南大学生命科学技术学院生物医学工程研究所四楼，401室 内容提要： The first part of my talk will concern the thermodynamics and phase transformations in the Al-rich (containing 80-92 at.% Al) Al-TM-RE (TM=transition metals; RE=rare earth elements) glasses which are highlighted by their light-weight, tunable corrosion resistance and high fracture strength, greater than 800 MPa. Especially I will present plastic deformation induced nanocrystallization within shear bands and devitrification phase transformation pathway in Al glasses. By using a range of experimental techniques, including TEM, high-resolution TEM, SEM, XRD and DSC, efforts were made to correlate the atomic structure of Al glasses with the phase transformation mechanisms due to thermal annealing or plastic deformation. Then I will demonstrate a new approach that combines critical experiments, CALPHAD modeling and first principles calculations to determine phase equilibria and thermodynamics in several Al glass forming systems. The methodology and applications of CALPHAD and first principles will be introduced briefly. My recent first principle calculations on the thermodynamics of over 330 compounds in 15 Al-RE binary systems will also be presented. The calculated phase stabilities at T=0 K are in very good agreement with experimentally reported ones for the majority of the systems. Trends in lattice stability across the RE series are explained on the basis of inter-atomic bonding and strain. This study demonstrates that first principles calculations can be employed to (1) further examine and improve the experimentally established alloy phase diagrams; (2) provide accurate enthalpy data for stable and hypothetical compounds and structures; (3) avoid large distortion to phase diagrams due to use of empirical energy data commonly exercised in the CALPHAD community. In addition, thermodynamics and elasticity calculations of transition metals will also be presented. Finally I will present texture analysis and finite element simulations of commercial cutting tools that consists of WC-Co composite substrate with mutilayer coatings deposited by chemical vapor deposition (CVD). Coatings typically consist of layers of a-Al2O3 and TiCxN1-x that are each several microns thick. The microtexture of a variety of commercial coatings was determined using orientation imaging microscopy and then has been used as input for Object Oriented Finite Element simulations to compare the role of the texture and microstructure on the residual stresses in the coatings.