Metallographic structure, dendrite cell size and mechanical properties of Al-6.6 wt. pct. Si-0.6 wt. pct. Mg alloy, unidirectionally solidified under various solidification conditions, have been studied. It has been found that the transition from columnar to equiaxed structure occurs when the ratio of temperature gradient (G) to rate of solidification (R), G/R, is smaller than a constant value. Dendrite cell size has been measured to be proportional to the negative one-fourth power of the cooling rate, and has been also measured to be proportional to the 0.22 power of local solidification time. Tensile strength increases as the dendrite cell size decreases and the cooling rate increases. |
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