Effect of Friction Stir Processing on Microstructural, Mechanical, and Corrosion Properties of Al-Si12 Additive Manufactured Components

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.

Adhesively bonded joints in components manufactured via selective laser melting

“…Fine segregations of Si-precipitates form inside the saturated Al-matrix. 28,29 The melt tracks are highly visible which was already shown in several studies, 30,31 where the cooling rates differ. In those parabolic sections, a change in size of the AlSi grains results.…”

On the Friction Stir Processing of Additive‐Manufactured 316L Stainless Steel

“…A few studies already focused on FSP and FSW of additively manufactured aluminum alloys. [ 29–31 ] It was found that an increase in temperature during FSP and FSW, respectively, causes the agglomeration and coarsening of Si‐rich particles deteriorating the strength of the material. Fine Si networks formed in the rapid solidification process play a key role in the strengthening of additively manufactured aluminum alloys.…”

“…Recently, the feasibility of enhancing the mechanical properties of additively manufactured metals in general and 316 L stainless steel in particular via various SPD methods such as FSP, friction stir welding (FSW), equal channel angular extrusion/pressing (ECAE/P), and high‐pressure torsion (HPT) has attracted attention. [ 28–34 ] During SPD, fragmentation and recrystallization of additively manufactured microstructures led to the formation of ultrafine grained (UFG) materials showing outstanding mechanical behavior. A very recent study showed that FSP has a great potential toward enhancing mechanical properties of additively manufactured 316 L stainless steel as this process could improve tensile strength by 18% with only minimum loss in ductility.…”

Electrochemical Investigation of the Effect of Process Parameters on the Corrosion Behavior of Aluminum-Cladded Pressure Vessel Steel Using a Friction Stir Diffusion Cladding Process

“…Furthermore, in a recent study by Anas et al [30], corrosion resistance was found to increase with a reduction in crystal size. Similarly, Moeini et al [31] reported enhancement in corrosion resistance in underwater FSP as compared to in-air FSP of additive manufactured Al-Si 12, due to a higher cooling rate that led to a more corrosion-resistant microstructure. The corrosion-protection mechanism may vary between metals and alloys, with finer grains resulting in increasing surface energy, therefore it can be a positive for surfaces that build a passive layer and at the same time a negative [28].…”