The scales of both, SDAS and intermetallics, can be predetermined to a measurable extent through the solute content to best suit particular casting conditions. The latter ones are more sensitive to cooling rate than the ones involving solute in solution. 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. 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. Cu showed its strongest refining effect at low-Si and high-Fe contents. For a given cooling rate, Si has a strong, consistently refining effect on the SDAS per unit of solute content. 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. Peak temperatures at position of -14 mm from centre line during weld. 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. X-rays are produced when high-speed electrons strike the atoms o f another substance.
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