Measurements of Microstructural, Mechanical, Electrical, and Thermal Properties of an Al-Ni Alloy

The Al-7.5 wt% Ni alloy was directionally solidified upwards with different temperature gradients, ( to at a constant growth rate, (. The dependence of dendritic microstructures such as the primary dendrite arm spacing (), the secondary dendrite arm spacing (), the dendrite tip radius (), and the mushy zone depth () on the temperature gradient were analyzed. The dendritic microstructures in this study were also compared with current theoretical models, and similar previous experimental results. Measurements of the microhardness (HV) and electrical resistivity () of the directionally solidified samples were carried out. Variations of the electrical resistivity () with temperature () were also measured by using a standard dc four-point probe technique. And also, the dependence of the microhardness and electrical resistivity on the temperature gradient was analyzed. According to these results, it has been found that the values of HV and increase with increasing values of . But, the values of HV and decrease with increasing values of dendritic microstructures ( and ). It has been also found that, on increasing the values of temperature, the values of increase. The enthalpy of fusion () for the Al-7.5 wt%Ni alloy was determined by a differential scanning calorimeter from a heating trace during the transformation from solid to liquid.