Abstract
Corrosion properties of two Al–Si alloys processed by Rheo-high pressure die cast (HPDC) method were examined using polarization and electrochemical impedance spectroscopy (EIS) techniques on as-cast and ground surfaces. The effects of the silicon content, transverse and longitudinal macrosegregation on the corrosion resistance of the alloys were determined. Microstructural studies revealed that samples from different positions contain different fractions of solid and liquid parts of the initial slurry. Electrochemical behavior of as-cast, ground surface, and bulk material was shown to be different due to the presence of a segregated skin layer and surface quality.
Highlights
High pressure die casting (HPDC) is one of the most used manufacturing process for light alloy components [1,2], due to its high productivity, capability to cast complex geometry, dimensional accuracy, reduced need for finishing operations, and producing component with fine grain microstructure and good mechanical properties [3,4,5].Coupling semisolid metal (SSM) casting to high pressure die cast (HPDC) (SSM-HPDC) is a promising technology to produce high quality components with sound microstructure
Rheocasting can be coupled with high pressure die casting and Rheo-HPDC parts have a globular microstructure and usually show low porosity
The present study focused on the Al low Si alloys produced by Rheo-HPDC process and on the effect of the microstructure inhomogeneity on the corrosion resistance
Summary
High pressure die casting (HPDC) is one of the most used manufacturing process for light alloy components [1,2], due to its high productivity, capability to cast complex geometry, dimensional accuracy, reduced need for finishing operations, and producing component with fine grain microstructure and good mechanical properties [3,4,5].Coupling semisolid metal (SSM) casting to HPDC (SSM-HPDC) is a promising technology to produce high quality components with sound microstructure. Higher viscosity of semisolid material in this process reduces air entrapment and consequent porosity in the component. Such a technology introduces a new opportunity to enhance the castability of a component, which is impossible to achieve by traditional manufacturing methods [2,3,6,7]. Rheocasting can be coupled with high pressure die casting and Rheo-HPDC parts have a globular microstructure and usually show low porosity. This leads to heat treatability and high performance [2,6]. Hypoeutectic Al–Si alloys in the range of 5–8% silicon content are suitable choices for this process [11]
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