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Prof N G Jones

Solidification processing is of considerable industrial importance. It is extensively used for metals, and also for polymers and semiconductors. In most cases, the rate at which solidification occurs is controlled by the heat flow. However, there are also important solute redistribution phenomena, particularly in metallic alloys and semiconductors, and there is often a complex interplay between heat flow, microstructure (including dendrite structure) and defect production (such as porosity and hot cracking). An understanding of the science of solidification is therefore essential for optimisation of these processes. A brief overview is given at the end of the course of a selection of important solidification processes.

This lecture course will cover:

  • Solidification Growth Kinetics. Free energy changes. Entropy of fusion and facetting. Continuous and lateral growth modes. Growth velocities and undercoolings for continuous growth.
  • Interface Stability & Dendrite Formation. Solute redistribution and constitutional undercooling. Dendritic and grain structures. Easy growth directions. Primary spacings. Marginal stability and fastest-growing wavelengths.
  • The Mushy Zone. Dendrite coarsening in the mushy zone. Mushy zone characteristics. Back-diffusion in the solid. Effect of heat flow on the mushy zone.
  • Eutectic Growth. Usage of eutectics. A model for coupled eutectic growth. Extremum growth. Eutectic microstructures. Anomalous eutectics.
  • Control of Cast Structure. Heat flow and interfacial heat transfer. Heat flow regimes. Mushy zone characteristics. Defect formation. Porosity. Hot cracking.
  • Selected Solidification Processes. Continuous casting of steel. Semi-continuous casting of aluminium. Czochralski growth of single crystals. Zone melting and the floating zone process.