Thermal and microstructural parameters in the transient solidification of Al-Mg and Al-Mg-Si alloys and correlation with mechanical and corrosion resistances

Abstract

The mechanical characteristics (strength under static and dynamic loading; wear resistance) and chemical characteristics (corrosion resistance) of as solidified metallic components depend on the microstructural arrangement, i.e. grain size and cellular and dendritic spacings; non-homogeneity of chemical composition; size, morphology and distribution of inclusions; porosity, etc. Additionally to the barriers to slip formed by the grain boundaries there are also obstacles between the cellular and dendritic arms. The development of correlations between the as-solidified microstructure and the corresponding properties can be a complex task, which depends on a careful experimental development with a view to determining accurate solidification thermal parameters. The present study aims to develop of a theoretical/ experimental analysis dealing with the effect of transient thermal parameters in the solidification of Al-Mg and Al-Mg-Si alloys on the microstructure development and on macrosegregation profiles, correlations between microstructural parameters and mechanical and corrosion resistances will be established with a view to permitting solidification operational conditions to be pre-programmed in order to allow the casting to attain a determined level of final properties. The experimental sequence will be developed as follows: vertical upward and downward transient directional solidification of Al-Mg and Al-Mg-Si alloys; determination of solidification thermal parameters; development of experimental dendritic growth laws; determination of macrosegregation profiles along the castings length; assessment of mechanical and corrosion properties as a function of the dendritic arm spacing and/or other quantitative aspect of phases forming the as-solidified microstructure. (AU)