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EFFECTS OF Ni ADDITIONS ON THE MECHANICAL PROPERTIES AND CORROSION RESISTANCE OF Al-Cu-Si ALLOY
Abstract:
This study was aimed at investigating the influence of Ni addition on the mechanical properties and corrosion characteristics of Al-Cu-Si alloy and the prime focus was to obtain a material that possessed good mechanical properties with adequate corrosion resistance. In this research, gravimetric and linear polarization methods were used to assess the corrosion behavior of the alloy in 3.5%NaCl. Microstructural properties of the coupons were studied with the aid of optical metallurgical microscope, while hardness and impact strength were measured with Rockwell scale F universal testing machine and Hounsfield impact tester machine respectively. The results obtained from both gravimetric and linear polarization indicates that corrosion resistance of the alloy was enhanced by Ni addition and thermal treatment. The reason might be due to the formation of intermetallics such as NiAl3 and Ni3Si, which passivate easily to form oxides that protect the alloy from further corrosion; and also the enveloping of the cathodic intermetallics by the α-matrix—a process called shingling may be responsible for improvement in the corrosion resistance of the alloy. The hardness of the alloy also increased with Ni up to a maximum of 2.5%Ni and then decreased, while the impact strength tends to decrease with increasing Ni content. The rise in hardness may equally be associated with the intermetallic compounds that are formed which tend to pin-down dislocation movement and hence higher hardness was achieved.
EFFECTS OF Ni ADDITIONS ON THE MECHANICAL PROPERTIES AND CORROSION RESISTANCE OF Al-Cu-Si ALLOY
