Abstract
The paper presents relationships between the degree of structure fineness and feeding quality of the Al – 20 wt.% Zn (Al-20 Zn) alloy cast
into a mould made from sand containing silica quartz as a matrix and bentonite as a binder, and its damping coefficient of the ultrasound
wave at frequency of 1 MHz. The structure of the examined alloy was grain refined by the addition of the refining Al-3 wt.% Ti – 0.15
wt.%C (TiCAl) master alloy. The macrostructure analysis of the initial alloy without the addition of Ti and the alloy doped with 50-100
ppm Ti as well as results of damping experiments showed that the structure of the modified alloy is significantly refined. At the same time,
its damping coefficient decreases by about 20-25%; however, it still belongs to the so called high-damping alloys. Additionally, it was
found that despite of using high purity metals Al and Zn (minimum 99,99% purity), differences in the damping coefficient for samples cut
from upper and bottom parts of the vertically cast rolls were observed. These differences are connected with the insufficient feeding
process leading to shrinkage porosity as well as gases present in metal charges which are responsible for bubbles of gas-porosity.
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