Study The Inclusion In The Aluminium Alloys

Metallographic microscope, scanning electronic microscope (SEM), energy disperse spectroscopy (EDS) and other means were employed in this paper to study the microstructure, the inclusions morphology and the inclusions contents as the aluminum scraps were added into the pure aluminum. An electric resistance furnace was used to melt ZL102, ZL114, A27 and 55Al-Zn-1.6Si alloys. After the furnace were completely drained and opened up, the residues of mentioned above alloys were studied. Base on inclusions contents analysis, mechanical property test and electrochemical test were carried out to study the mechanical property and corrosion behavior of pure aluminum which was introduced inclusions by addition of different contents (0%, 20%, 40%, 60%, 80%, and 100%) aluminum scraps. The main test results as follows:(1) The results of SEM and EDS show that there are lots of inclusions with shrinkage porosities in the residues. The morphology and dimension of inclusions are irregular. The inclusions exist on the grain boundary or the local zone of the microstructure, and aggregate as clusters or flake.(2) Dynamic potential scanning and linear polarization was employed to measure the electrochemical parameters such as E_k, R_p, and I_corr. The results show that the Tafel curves move right, the linear polarization resistances decrease, the corrosion potentials move to positive, and the corrosion currency increases with the increase of aluminum scraps (namely the inclusion contents are increasing).(3) The results of optical SEM fracture analysis and Leica optical microscope (OM) analysis indicate that the inclusions and shrinkage porosities which exist in the microstructure increase as the increasing of aluminum scraps which were added into the pure aluminum by contents of 0%, 20%, 40%, 60%, 80%, and 100%(4) The mechanical properties testing results show that the Vickers hardness of alloys are increasing with the increase of aluminum scraps, but the ductibility and the tensile strength are decreasing, in particular, the percentage elongation decrease rapider.(5) Comparing the result of electrochemical test with the result of OM analysis, and adopting regression analysis, we find that there is a corresponding relationship between the electrochemical parameters (corrosion potentials) and inclusion contents. The correlation coefficient is close to 0.9995. Based on this result, it is concluded that we can adopt electrochemical parameters to assess the inclusion contents which exist in aluminum alloy.