Solidification of metal alloys in pulse electromagnetic fields

This research studies the evolution of solidification microstructures in applied external physical fields including in a pulse electric current plus a static magnetic field, and a pulse electromagnetic field. A novel electromagnetic pulse device and a solidification apparatus were designed, built and commissioned in this research. It can generate programmable electromagnetic pulses with tuneable amplitudes, durations and frequencies to suit different alloys and sample dimensions for research at university laboratory and at synchrotron X-ray beamlines.Systematic studies were made using the novel pulse electromagnetic field device, together with finite element modelling of the multiphysics of the pulse electromagnetic field and microstructural characterisation of the samples made using scanning electron microscopy, X-ray imaging and tomography.The research demonstrated that the Lorentz force and magnetic flux are the dominant parameters for achieving the grain refinement and enhancing the solute diffusion. At a discharging voltage from 120 V, a complete equaxied dendritic structure can be achieved for Al-15Cu alloy samples, the strong Lorentz force not only disrupts the growing direction of primary dendrites, it is also enough to disrupts the growing directions of primary intermetallic Al2Cu phases in Al-35Cu alloy, resulting a refined solidification microstructures. The applied electromagnetic field also has significant effect on refining the eutectic structures and promoting the solute diffusion in the eutectic laminar structure.The research has demonstrated that the pulse electromagnetic field is a promising green technology for metal manufacture industry

Solidification of Al alloys under electromagnetic pulses and characterization of the 3D microstructures under synchrotron x-ray tomography

A novel programmable electromagnetic pulse device was developed and used to study the solidification of Al-15 pct Cu and Al-35 pct Cu alloys. The pulsed magnetic fluxes and Lorentz forces generated inside the solidifying melts were simulated using finite element methods, and their effects on the solidification microstructures were characterized using electron microscopy and synchrotron X-ray tomography. Using a discharging voltage of 120 V, a pulsed magnetic field with the peak Lorentz force of ~1.6 N was generated inside the solidifying Al-Cu melts which were showed sufficiently enough to disrupt the growth of the primary Al dendrites and the Al2Cu intermetallic phases. The microstructures exhibit a strong correlation to the characteristics of the applied pulse, forming a periodical pattern that resonates the frequency of the applied electromagnetic field