Impact of convection on the damping of an oscillating droplet during viscosity measurement using the ISS-EML facility.

Oscillating droplet experiments are conducted using the Electromagnetic Levitation (EML) facility under microgravity conditions. The droplet of molten metal is internally stirred concurrently with the pulse excitation initiating shape oscillations, allowing viscosity measurement of the liquid melts based on the damping rate of the oscillating droplet. We experimentally investigate the impact of convection on the droplet's damping behavior.

Numerical representations for flow velocity and shear rate inside electromagnetically levitated droplets in microgravity.

Electromagnetic levitation techniques are used in a microgravity environment to allow materials research under containerless conditions while limiting the influence of gravity. The induced advective flow inside a levitated molten alloy droplet is a key factor affecting solidification phenomena while potentially influencing the measurement of thermophysical properties of metallic alloy. It is thus important to predict the flow velocity under various operation conditions during melt processing.

Microgravity experiments on the effect of internal flow on solidification of Fe-Cr-Ni stainless steels.

A new hypothesis has been developed to explain the effect of internal fluid flow on the lifetime of a metastable phase in solidifying Fe-Cr-Ni alloys. The hypothesis shows excellent agreement with available experimental results, but microgravity experiments are required for complete validation. Certain Fe-Cr-Ni stainless steel alloys solidify from an undercooled melt by a two-step process in which the metastable ferrite phase forms first followed by the stable austenite phase.

Convection in containerless processing.

Different containerless processing techniques have different strengths and weaknesses. Applying more than one technique allows various parts of a problem to be solved separately. For two research projects, one on phase selection in steels and the other on nucleation and growth of quasicrystals, a combination of experiments using electrostatic levitation (ESL) and electromagnetic levitation (EML) is appropriate.

Contrasting electrostatic and electromagnetic levitation experimental results for transformation kinetics of steel alloys.

The delay between conversion of metastable ferrite to stable austenite during ternary Fe-Cr-Ni alloy double recalescence is seen to differ by over an order of magnitude for tests conducted using electrostatic and electromagnetic levitation. Several possible reasons for this deviation are proposed. Thermodynamic calculations on evaporation rates indicate that potential composition shifts during testing are minimized by limiting test time and thermal history.