71 research outputs found
Characterization and Calibration of the CheMin Mineralogical Instrument on Mars Science Laboratory
Simple, expedient methods for the determination of water and electrolyte contents of cellulose solvent systems
Microtubule organization differs between acid and alkaline bands in internodal cells ofChara but bands can develop in the absence of microtubules
Alloy composition and dendrite arm spacing in Al-Si-Cu-Mg-Fe alloys
Six Al-Si-Cu-Mg-(Fe/Mn) alloys with two levels of each of Cu, Si, and Fe/Mn were cast in the form of quasi-directionally solidified plates. The secondary dendrite arm spacing (SDAS) was measured as a function of the distance from the chill end for each composition and related to the local cooling rate as determined by thermocouples embedded in one of the cast plates. For a given cooling rate, Si has a strong, consistently refining effect on the SDAS per unit of solute content. Cu showed its strongest refining effect at low-Si and high-Fe contents. It is argued that the scale of the SDAS is determined by a combination of five main factors: constitutional undercooling; the fraction of Al-Si eutectic; and the amount, morphology, and distribution of the various intermetallic phases. The first two factors affect the early stages of the dendrite structure and SDAS formation, whereas the ones involving intermetallics affect the dendrite-coarsening mechanisms in the post-eutectic stage. The latter ones are more sensitive to cooling rate than the ones involving solute in solution. The scales of both, SDAS and intermetallics, can be predetermined to a measurable extent through the solute content to best suit particular casting conditions. (C) The Minerals, Metals & Materials Society and ASM International 201
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