Application of Inverse Methods to the Estimation of Boundary Conditions and Properties

Inverse methods can be used in solidification and related processes for the estimation of boundary conditions or physical properties of materials. For heat flow problems, these methods are based upon a minimisation of the errors between calculated and measured temperatures at given locations and times of the space-time domain, the calculated values being obtained from a numerical solution of the heat flow equation. In the present case, a maximum a posteriori technique has been implemented into a finite element code. This method is then applied to several situations for the determination of : i) the time-dependent heat-transfer coefficient at the surface of a steel rod which has been water-cooled after induction heating (non-stationary situation) ; ii) the space-dependent heat flow at the surface of a direct chill cast aluminium slab (stationary situation) ; and iii) the temperature-dependent thermal conductivity of aluminium-silicon alloys. In this latter case, the influence of the silicon concentration on the thermal conductivity is clearly revealed

Some Consequences of Thermosolutal Convection: The Grain Structure of Castings

The essential principles of thermosolutal convection are outlined, and how convection provides a transport mechanism between the mushy region of a casting and the open bulk liquid is illustrated. The convective flow patterns which develop assist in heat exchange and macroscopic solute segregation during solidification; they also provide a mechanism for the transport of dendritic fragments from the mushy region into the bulk liquid. Surviving fragments become nuclei for equiaxed grains and so lead to blocking of the parental columnar, dendritic growth front from which they originated. The physical steps in such a sequence are considered and some experimental data are provided to support the argument