Papers by Author: David John Jarvis

Abstract: The authors are members of the integrated project Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS), funded within the European Framework (FP6). One of the aims of IMPRESS is to develop new alloys and processes for the casting of TiAl-based turbine blades for the next generation of aero and industrial gas turbine engines. Within IMPRESS, two related issues have been identified during the primary solidification stage, namely, segregation and the columnar-to-equiaxed transition (CET). The authors have set out to isolate the effects of thermo-solutal convection, by designing a microgravity experiment to be performed on a European Space Agency platform. This experiment will investigate the CET formation during solidification. It is planned to use a sounding rocket providing a microgravity time of approximately twelve minutes. The results of this microgravity solidification experiment will be used as unique benchmark data for development and validation of new computational models of TiAl solidification. This in turn will produce accurate models and ultimately new robust industrial processes by project partners in the aerospace industry. The evolution of the design of the microgravity experiment is discussed and the results of preliminary ground reference experiments are presented. Future plans and objectives for the project are also highlighted.

Abstract: Over the past five years, an application-oriented research strategy has been initiated by ESA to permit valuable microgravity research in a broad range of physical sciences. The main objective is to integrate ESA, national activities and industry into an overall European strategy, which will allow research to be performed aboard the International Space Station (ISS), as well as other microgravity platforms, like unmanned space capsules, sounding rockets and parabolic flights. A key area of microgravity research is centred on metallurgy in space. The principal aims of this research field are (i) to investigate various physical phenomena during solidification processes and (ii) to determine the thermophysical properties of important liquid alloys. A number of metallurgical sub-topics have been identified in the ESA research programme, including the columnar-to-equiaxed transition during solidification; metastable and non-equilibrium solidification; multiphase multicomponent alloy solidification; eutectic, peritectic, monotectic and intermetallic alloy growth; fluid flow effects on mushy zone formation; and the measurement of thermophysical properties of liquid alloys. This review paper will therefore highlight the theoretical, experimental and modelling efforts currently being undertaken in the ESA programme.