Abstract
Additive manufacturing by selective laser melting (AM-SLM) is an advanced manufacturing approach in which a structure is fabricated by successive thin powder layers melted by a focused laser beam. The aerospace and automotive sectors are especially interested in the AMSLM technology that enables quick production of complex and customized structures. AlSi10Mg alloy has been found to be applicable to AM-SLM mainly because good cast-ability, strong weldability and low shrinkage during solidification. While many studies on the quasi-static mechanical properties and the structure of SLM AlSi10Mg were published, there is limited published research focused on the dynamic properties of SLM AlSi10Mg under high rate strains. In addition to that, the shear strength of SLM aluminium alloys is rarely investigated. This study presents an investigation of the AM-SLM AlSi10Mg static and dynamic shear strength and its dependency on build direction. Experiments included quasi-static shear experiments performed according to the protocol of ASTM B565, and dynamic shear tests performed using a split Hopkinson pressure bar (SHPB), coupled to innovative punch assembly that generates pure dynamic shear loads on the sample. The design of this sample holder has been validated numerically and an experimentally. The quasi-static experiments revealed that the static shear strength is independent of build direction. In contrast, the dynamic tests demonstrated that the dynamic shear strength of vertically built samples is higher by almost 11% than the shear strength of samples built horizontally. This last phenomenon explained with a suggested mechanism based onelectron microscope fractography.
Highlights
Selective laser melting (SLM) of a powder bed is the most utilized manufacturing technique of additive manufacturing (AM) of metal alloys, known as 3D printing
The shear strength results for the XY oriented samples is 219 ± 4 MPa for the quasi static loading, and 221± 5 MPa for the medium range loading
This study presents the shear behavior of SLM AlSi10Mg under variable loading rate
Summary
Selective laser melting (SLM) of a powder bed is the most utilized manufacturing technique of additive manufacturing (AM) of metal alloys, known as 3D printing. The excellent characteristics during casting and welding makes the AlSi10Mg alloy suitable for the SLM process [1]. The SLM process affects the microstructure of the AlSi10Mg leaving microscopic laser metal tracks. Numerous studies which investigated the alloy’s quasi-static mechanical properties established that the strength and hardness of the SLM AlSi10Mg alloy is comparable or even higher than those obtained with convential cast alloy[3]. The scientific community became interested in the dynamic behavior of SLM AlSi10Mg. Using a split Hopkinson pressure bar (SHPB) apparatus, it was established that the alloy’s dynamic properties are sensitive to fabrication orientation. At strain rates in the range from 7×102 to 7×103 s-1, vertically built samples had 10% higher yield stress than samples manufactured horizontally and the alloy’s peak stress is slightly strain rate sensitive [2][5]
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