Experimental and numerical study of the cold crucible melting process

The cold crucible, or induction skull melting process as is otherwise known, has the potential to produce high purity melts of a range of difficult to melt materials, including Ti–Al and Ti6Al4V alloys for Aerospace, Ti–Ta and other biocompatible materials for surgical implants, silicon for photovoltaic and electronic applications, etc. A water cooled AC coil surrounds the crucible causing induction currents to melt the alloy and partially suspend it against gravity away from water-cooled surfaces. Strong stirring takes place in the melt due to the induced electromagnetic Lorentz forces and very high temperatures are attainable under the right conditions (i.e., provided contact with water cooled walls is minimised). In a joint numerical and experimental research programme, various aspects of the design and operation of this process are investigated to increase our understanding of the physical mechanisms involved and to maximise process efficiency. A combination of FV and Spectral CFD techniques are used at Greenwich to tackle this problem numerically, with the experimental work taking place at Birmingham University. Results of this study, presented here, highlight the influence of turbulence and free surface behaviour on attained superheat and also discuss coil design variations and dual frequency options that may lead to winning crucible designs.

Macro-segregation of multi-component alloys in shape casting simulation

The objective of this work is to present a new scheme for temperature-solute coupling in a solidification model, where the temperature and concentration fields simultaneously satisfy the macro-scale transport equations and, in the mushy region, meet the constraints imposed by the thermodynamics and the local scale processes. A step-by-step explanation of the macrosegregation algorithm, implemented in the finite volume unstructured mesh multi-physics modelling code PHYSICA, is initially presented and then the proposed scheme is validated against experimental results obtained by Krane for binary and a ternary alloys.

Experimental and numerical study of the cold crucible melting process

The cold crucible, or induction skull melting process as is otherwise known, has the potential to produce high purity melts of a range of difficult to melt materials, including Ti–Al and Ti6Al4V alloys for Aerospace, Ti–Ta and other biocompatible materials for surgical implants, silicon for photovoltaic and electronic applications, etc. A water cooled AC coil surrounds the crucible causing induction currents to melt the alloy and partially suspend it against gravity away from water-cooled surfaces. Strong stirring takes place in the melt due to the induced electromagnetic Lorentz forces and very high temperatures are attainable under the right conditions (i.e., provided contact with water cooled walls is minimised). In a joint numerical and experimental research programme, various aspects of the design and operation of this process are investigated to increase our understanding of the physical mechanisms involved and to maximise process efficiency. A combination of FV and Spectral CFD techniques are used at Greenwich to tackle this problem numerically, with the experimental work taking place at Birmingham University. Results of this study, presented here, highlight the influence of turbulence and free surface behaviour on attained superheat and also discuss coil design variations and dual frequency options that may lead to winning crucible designs.

Modeling the diffusion of solid copper into liquid solder alloys

During the soldering process, the copper atoms diffuse into liquid solders. The diffusion process determines integrity and the reworking possibility of a solder joint. In order to capture the diffusion scenarios of solid copper into liquid Sn–Pb and Sn–Cu solders, a computer modeling has been performed for 10 s. An analytical model has also been proposed for calculating the diffusion coefficient of copper into liquid solders. It is found that the diffusion coefficient for Sn–Pb solder is 2.74 × 10− 10 m2/s and for Sn–Cu solder is 6.44 × 10−9 m2/s. The modeling results reveal that the diffusion coefficient is one of the major factors that govern the rate at which solid Cu dissolve in the molten solder. The predicted dissolved amounts of copper into solders have been validated with the help of scanning electron microscopic analysis.