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

ENGİN S., BÖYÜK U., KAYA H., MARAŞLI N.

INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS, cilt.18, sa.6, ss.659-664, 2011 (SCI-Expanded) identifier identifier

Özet

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.

Zn-5wt.%Al eutectic alloy was directionally solidified upwards with different growth rate (5.32 to 250.0 micro m/s) at constant temperature gradient (8.50 K/mm) using a Bridgman–type growth apparatus. The values of eutectic spacing (???was measured from transverse sections of the samples. The dependence of eutectic spacing on the growth rate (V) and undercoolings (?T) was determined. The results obtained in this work have been compared with the Jackson-Hunt eutectic theory and the similar experimental results in the literature. Microhardness (HV) of directionally solidified samples was also measured by using microhardness test device. Dependency of the HV on V was investigated. Afterwards, variations of electrical resistivity of casting alloy with the temperature (T) in the range of 300?630 K were measured. The enthalpy of fusion and specific heat (Cp) for the Zn-Al eutectic alloy was determined by means of differential scanning calorimeter (DSC) from heating trace during the transformation from liquid to solid.