RELATIONSHIP BETWEEN STRUCTURE AND PROPERTIES OF AL-CU ALLOYS

摘要

The objective of the present research consists on studying the type of structure (columnar, equiaxed or with columnar to equiaxed transition, CET) using parameters of the solidification process and electrochemical parameters in Al-Cu alloys with different concentrations. In order to obtain columnar, equiaxed and CET structures, the alloys were directionally solidified upwards in an experimental set up with a set of thermocouples in the samples which permit to determine the time dependent profiles of temperature during the process. The electrochemical studies of the samples were realized by using an electrochemical impedance spectroscopy (EIS) technique and potentio-dynamic polarization curves immersed in 3% NaCl solution at room temperature. In general, we observed that the susceptibility to corrosion of the different structures depends on the size of the secondary dendritic spacing and proportion of Al_2Cu phase and Al-rich phase.