Dendrite coherency is important to the formation of the solidification structure and castability of alloys. The effects of grain refinement on the dendrite coherency in A319 aluminum alloy have been studied using the two-thermocouple thermal analysis technique in the solidifying sample. The fraction solid at the dendrite coherency point ( f DCP s ) in the A319 alloy increases with increasing Al-5Ti-1B grain refiner, and varies from 16 to 21 pct when the amount of Al-5Ti-1B in the alloy is in the range of 0 to 4.6 wt pct. The results also indicate that the grain refinement increases the temperature interval of coherency (T N -T DCP ) and coherency time (t DCP ), and it can postpone dendrite coherency. These changes were interpreted based on the dendrite growth rate, the growth restriction factor, and the microstructure.
In the metal casting industry, an improvement of component quality depends mainly on better control over the production parameters. Thus, a thermal analysis cooling curve of the alloy is used for process control in the aluminum casting industry. In this research, the effect of seven different cooling rates on the microstructure and solidification parameters of the 319 aluminum alloy have been investigated by means of thermal analysis. In each case, the cooling curve and its first derivative curve have been plotted by using very accurate thermal analysis equipment. The effect of different cooling rates on solidification parameters such as nucleation temperature (T N,a ), nucleation undercooling (DT N,a ), recalescence temperature (T R,a ), solidification range (DT s ) and total solidification time (t f ) has been studied in the liquidus region. Microstructural evaluation has been carried out and DAS was measured in all solidification conditions.
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