Phase Formation Modeling of an Alloy 706 Casting Using Computational Thermodynamics
Computational thermodynamics to perform alloy and process modeling for Ni-based superalloys is a new technology which has become available to industry. This paper presents an application of the technology to a superalloy of current interest. The objective of this paper is to show how results obtained from the computational program Thermo-Calc ‘1 using a recently developed thermodynamic database for Ni-based superalloy9 can be applied to help understand solidification in INCONEL’ alloy 706. The ability of the computational method to predict both stable and metastable phase formation is explored. INCONEL@ alloy 706 was chosen because of its importance in the manufacture of large land-based gas turbine disks. In addition, the alloy’s complex structure tested the viability of the computational method. The phases examined were: Laves, MC carbide, and the y matrix. Quantitative microstructure evaluation and X-ray dispersive analysis were performed on an as-cast, vacuum induction melted (VIM) ingot. Differential Thermal Analysis (DTA) was performed on selected samples of the alloy. The experimental data was compared to the data generated via the computational approach. TM Thermo-Calc, trade name of the Division of Computational Thermodynamics, Royal Institute of Technology, Stockholm, Sweden. 8 INCONEL is a trademark of the INCO group of companies.
Numerical and physical simulation of rapid microstructural evolution of gas atomised Ni superalloy powders
Abstract The rapid microstructural evolution of gas atomised Ni superalloy powder compacts over timescales of a few seconds was studied using a Gleeble 3500 thermomechanical simulator, finite element based numerical model and electron microscopy. The study found that the microstructural changes were governed by the characteristic temperatures of the alloy. At a temperature below the γ' solvus, the powders maintained dendritic structures. Above the γ' solvus temperature but in the solid-state, rapid grain spheroidisation and coarsening occurred, although the fine-scale microstructures were largely retained. Once the incipient melting temperature of the alloy was exceeded, microstructural change was rapid, and when the temperature was increased into the solid + liquid state, the powder compact partially melted and then re-solidified with no trace of the original structures, despite the fast timescales. The study reveals the relationship between short, severe thermal excursions and microstructural evolution in powder processed components, and gives guidance on the upper limit of temperature and time for powder-based processes if desirable fine-scale features of powders are to be preserved.
Transnational variation in linguistic politeness in Vietnamese : Australia and Vietnam
Over the past three decades, the Vietnamese language has undergone substantial changes, both in Vietnam, and in diasporic contexts such as Australia. Yet the nature of the variation resulting from those changes at the sociopragmatic level in expressing politeness is little researched. 
The question of whether there are differences in the politeness expressed by Vietnamese speakers living in Vietnam and Australia is the focus of this research.