Abstract
Additive manufacturing (AM) is an advanced manufacturing process that provides the opportunity to build geometrically complex and highly individualized lightweight structures. Despite its many advantages, additively manufactured components suffer from poor surface quality. To locally improve the surface quality and homogenize the microstructure, friction stir processing (FSP) technique was applied on Al-Si12 components produced by selective laser melting (SLM) using two different working media. The effect of FSP on the microstructural evolution, mechanical properties, and corrosion resistance of SLM samples was investigated. Microstructural investigation showed a considerable grain refinement in the friction stirred area, which is due to the severe plastic deformation and dynamic recrystallization of the material in the stir zone. Micro-hardness measurements revealed that the micro-hardness values of samples treated using FSP are much lower compared to SLM components in the as-built condition. This reduction of hardness values in samples treated with FSP can be explained by the dissolution of the very fine Si-phase network, being characteristic for SLM samples, during FSP. Surface topography also demonstrated that the FSP results in the reduction of surface roughness and increases the homogeneity of the SLM microstructure. Decreased surface roughness and grain size refinement in combination with the dissolved Si-phase network of the FSP treated material result in considerable changes in corrosion behavior. This work addresses the corrosion properties of surface treated additive manufactured Al-Si12 by establishing adequate microstructure-property relationships. The corrosion behavior of SLM-manufactured Al-Si12 alloys is shown to be improved by FSP-modification of the surfaces.
Highlights
Technology to produce components with high efficiency and functional properties in a relatively short time and at lower costs is the main demand of most industries
From the SEM micrographs of the samples, focusing on the selective laser melting (SLM) as-built condition as well as the stir zone and the thermomechanically affected zone (TMAZ) upon Friction stir processing (FSP) (Figure 1), it can be deduced that a Si-rich network of cellular shape is present in the SLM aluminum matrix
The microstructure of the AC-FSP state is characterized by spheroidized Si-rich particles, with relatively high inter-particle distance, while in the UW-FSP state the Si-rich particles are significantly finer and different in shape, i.e., mostly acicular
Summary
Technology to produce components with high efficiency and functional properties in a relatively short time and at lower costs is the main demand of most industries. Additive manufacturing (AM) as a direct manufacturing technology provides the opportunity to produce high-performance components characterized by complex geometry directly from computer-aided design (CAD) data. Selective laser melting (SLM) is the powder bed fusion additive manufacturing technique most frequently used for AM of aluminum alloys [1]. Due to the layer-wise nature of additive manufacturing, the components show poor surface quality. To improve the surface quality, different aspects related to AM processing as well as post-processing techniques were studied [2,3,4,5,6,7,8,9,10,11,12]
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