Interrelation of solidification thermal and microstructural parameters and the Tribocorrosive behavior of Al-Zn (mg) and Zn-Mg alloys

Abstract

With the comprehension of microstructural parameters of alloys directionally solidified under transient heat flow conditions, it is possible to envisage components having better properties and higher lifetime. A careful study, permitting correlations between these microstructural parameters and mechanical, wear, corrosion and tribocorrosion behavior of metallic alloys to be established, is fundamental in the pre-programming of final properties of as-cast components. Binary Al-Zn and Zn-Mg alloys, are typically used for protective coatings of steel parts, particularly in the automotive and civil construction industries, and as sacrificial anodes due to their inherent corrosion stability, besides the potential of use of Zn-Mg alloys in biomedical implants mainly due to the presence of Mg, a nontoxic and biodegradable material. However, there are no systematic studies in the literature on the evolution of solidification microstructures under transient heat flow conditions and on correlations between the scale of parametric features of these microstructures and application properties such as wear and corrosion resistances. The present study aims to develop a detailed analysis of the microstructural evolution (through optical and scanning microscopy characterization) of different compositions of Al-Zn alloys (in the range up to 5wt%Zn and also by alloying with Mg permitting an intermetallics to be incorporated in the analysis) and of Zn-Mg alloys (in the range up to 5wt%Mg) directionally solidified under transient conditions. The study also aims to establish growth laws correlating quantitative parameters of the microstructure and solidification thermal parameters. Furthermore, representative specimens of each alloy examined having different microstructural scales (e.g. dendritic or interphase spacings) will be subjected to corrosion and tribocorrosion tests with a view to determining correlations between these microstructures and the corresponding corrosion and tribocorrosion behavior. The tribocorrosion tests will be carried out in the Centro Nacional de Investigaciones Metalurgicas - CENIM de Madrid, through a scientific partnership already established. (AU)