Thixoforming technology requires a feedstock with a globular microstructure
rather than dendritic microstructure used in conventional casting
methods. In the present investigation, several AA7075 wrought aluminum
alloy feedstock were produced using cooling slope (CS) casting technique
at different fabrication conditions. Optimization of the CS castingprocess
parameterswas conductedto find out the optimum conditionsthat achieve
the best microstructural characteristics of the feedstock. Moreover, correlations
for microstructural characteristics as functions of CS casting
process parameters were determined. The results revealed that the optimum
values of pouring temperature, cooling length and tilt angle were
found to be 650 °C, 350 mm and 45°, respectively. Billets fabricated under
such conditions showed the minimum average size as well as the maximum
shape factor of á-Al primary grains. The pouring temperature is the
most influential parameter on both the average grain size and shape factor
of the primary á-Al grains.The developed empirical correlations were successfully
used to predict the average grain size and shape factor of the
AA7075 alloy billets produced using CS casting technique. |
