<p>Metal additive manufacturing is a rapidly growing technology revolutionizing many industries, yet wide adoption is limited due to the unreliability and complexity of the process. Scanning strategies, such as hatching, add further complexity to heat transfer and ultimately microstructure growth. Applying external magnetic fields is a promising technique to improve control of melt flow and heat transfer. High local thermal gradients can cause thermoelectric currents to circulate at the solid–liquid interface. When a magnetic field is applied, a Lorentz force drives fluid flow, which can have a significant impact on the melt behavior and solidification outcome. In this work, we analyze the impact that a static magnetic field has on liquid metal flow using a scale model representative of additive manufacturing, which allows us to directly observe and measure the thermoelectric magnetohydrodynamic flow. Experiments with a bi-metallic bowl, made of two halves with distinctly different thermo-physical properties, provides an analogy to hatching, revealing a strong influence on both thermoelectric currents and, ultimately, the flow. Through an analytic scaling analysis, the results are compared against numerical models spanning orders of magnitude in both length and velocity, providing a correlation between the model experiment and realistic conditions encountered in industry additive manufacturing processes.</p>

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Model Experiment for the Investigation of Thermoelectric Magnetohydrodynamics in Metal Additive Manufacturing

  • Imants Kaldre,
  • Valdemars Felcis,
  • Ivars Krastins,
  • Peter Soar,
  • Catherine Tonry,
  • Andrew Kao

摘要

Metal additive manufacturing is a rapidly growing technology revolutionizing many industries, yet wide adoption is limited due to the unreliability and complexity of the process. Scanning strategies, such as hatching, add further complexity to heat transfer and ultimately microstructure growth. Applying external magnetic fields is a promising technique to improve control of melt flow and heat transfer. High local thermal gradients can cause thermoelectric currents to circulate at the solid–liquid interface. When a magnetic field is applied, a Lorentz force drives fluid flow, which can have a significant impact on the melt behavior and solidification outcome. In this work, we analyze the impact that a static magnetic field has on liquid metal flow using a scale model representative of additive manufacturing, which allows us to directly observe and measure the thermoelectric magnetohydrodynamic flow. Experiments with a bi-metallic bowl, made of two halves with distinctly different thermo-physical properties, provides an analogy to hatching, revealing a strong influence on both thermoelectric currents and, ultimately, the flow. Through an analytic scaling analysis, the results are compared against numerical models spanning orders of magnitude in both length and velocity, providing a correlation between the model experiment and realistic conditions encountered in industry additive manufacturing processes.