Directional solidification and physical properties measurements of the zinc-aluminum eutectic alloy

Engin S., Boyuk U., KAYA H., Marasli N.

INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS, vol.18, no.6, pp.659-664, 2011 (SCI-Expanded) identifier identifier


Zn-5wt% Al eutectic alloy was directionally solidified with different growth rates (5.32-250.0 mu m/s) at a constant temperature gradient of 8.50 K/mm using a Bridgman-type growth apparatus. The values of eutectic spacing were measured from transverse sections of the samples. The dependences of the eutectic spacing and undercooling on growth rate are determined as lambda=9.21V(-0.53) and Delta T=0.0245V(0.53), respectively. The results obtained in this work were compared with the Jackson-Hunt eutectic theory and the similar experimental results in the literature. Microhardness of directionally solidified samples was also measured by using a microhardness test device. The dependency of the microhardness on growth rate is found as Hv=115.64V(0.13). Afterwards, the electrical resistivity (r) of the casting alloy changes from 40x10(-9) to 108x10(-9) Omega.m with the temperature rising in the range of 300-630 K. The enthalpy of fusion (Delta H) and specific heat (C(p)) for the Zn-Al eutectic alloy are calculated to be 113.37 J/g and 0.309 J/(g.K), respectively by means of differential scanning calorimetry (DSC) from heating trace during the transformation from liquid to solid.