Abstract
In this study, Al-xZn (x=1, 3, 5, 7, 10 and 20 wt. %) alloys were prepared using metals of 99.99% high purity in the vacuum atmosphere. These alloys were directionally solidified upward with a constant temperature gradient, G (10.3 K/mm) and different growth velocities (V) between 8.25 and 165 µm/s in the directional solidification apparatus. The experimental results have revealed that with the increase of the growth velocity of the melts from 8.25 µm/s to 165 µm/s, the microstructures undergo a transition from cellular/cellular dendritic morphology to coarse dendritic form for each composition (Zn content, Co). The measurements of microhardness (HV) of the specimens were performed by using a microhardness test device. The dependence of HV on V and Co was analyzed, and it has been found that with increasing the V and Co the HV increases. Relationships between HV-V and HV-Co were obtained by linear regression analysis, and the experimental results were compared with the results of previous similar works.
Highlights
Aluminum alloys are used in industry because of their corrosion resistance, low specific weight, heat and electrical conductivity
The estimated error in the microhardness measurements with statistical data analysis is about 5%. These researchers found that the microhardness increased from 450 to 730 MPa with the increase of Zn content
As can be seen from the exponent values in the obtained relationships, the effect of Zn content at a constant G and given V is more effective on the microhardness of the studied alloys than the growth velocity at a constant G and Zn content
Summary
Aluminum alloys are used in industry because of their corrosion resistance, low specific weight, heat and electrical conductivity. These properties make them valuable for use in various industrial applications, and researchers have been actively exploring new application for these alloys[1,2,3]. Aluminum has a cubic structure with centered face and is slightly anisotropic whereas zinc has a hexagonal structure and is strongly anisotropic. This difference in anisotropy involves a variation of interfacial energy modifying morphologies and directions of dendritic growth. Some studies[12,13,14] have reported monolithic β and distinctive α + β phases in high Zn containing and heat treatment applied alloys
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