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Abstract: The purpose
of this study is to develop a new image processing technique to evaluate decanted
structures of undercooled alloys. Dendrite growth theory reveals a trend of decreasing
dendrite radii as undercooling levels increases and a similar decreasing trend with
increasing convection rates at lower undercoolings. Experiments were performed to
evaluate if optical microscopy could ... read morebe used to quantify decanted surface structures
following rapid solidification of eutectic CoSi62 at% alloys. Dendrite diameters
decrease with increasing undercooling except for tests conducted with applied stirring
at low undercoolings. The higher the convection, the greater the deviation. Marangoni
stirring was induced by irradiating a small target area on the surface of levitated
molten samples. For a 0.5W laser input, the characteristic diameter was half the
unstirred value. For 2.4 W laser input this factor drops to one third. The developed
imaging technique was able to produce these trends when identifying the primary
phases.
Thesis (M.S.)--Tufts University,
2018.
Submitted to the Dept. of Mechanical
Engineering.
Advisor: Douglas
Matson.
Committee: Luisa Chiesa, and Darryl
Williams.
Keyword: Mechanical
engineering.read less
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