Martin Fehlbier

Influence of convection and grain movement on globular equiaxed solidification

Abstract A two-phase volume averaging model was used to study convection and grain movement, and their influence on the globular equiaxed solidification. Both liquid and solid phases were treated as separate interpenetrating continua. The mass, momentum, species and enthalpy conservation equations for each phase and a grain transport equation were coupled. An ingot casting (Al–4 wt.% Cu) with near globular solidification morphology was simulated. Case studies with different modeling assumptions such as with and without grain movement, and with slip and non-slip boundary conditions for solid phase were presented and compared. Understanding of grain evolution and macrosegregation formation in globular equiaxed solidification was improved.

NiAl – material for the application in gas turbines

Abstract NiAl alloys are very promising candidates for high-temperature applications such as turbine blades of gas turbines. For such turbine blades, investment casting is the common manufacturing process. Up to now, the processing of NiAl alloys in general and in particular via investment casting is hardly possible due to the very high melting temperature, hardness, reactivity of the melt, and a characteristic ductile-to-brittle transition temperature. In this publication, the development of an investment casting technology will be summarised including the shell mould and core development, casting process development, the advancement of numeric simulation tools, and the formulation of a complete data set.