Identification of AlSi10Mg matrix behavior by nanoindentation

Laser powder bed fusion (LPBF) is an additive manufacturing technique that is widely used to produce AlSi10Mg parts with a good strength-to-weight ratio and a very fine microstructure thanks to high cooling rates. However, to obtain better mechanical properties, a good ductility and higher fatigue resistance, post-treatments have to be performed.
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<br />In this work, friction stir processing, a thermomechanical post-treatment, is applied on an as-built plate of 5 mm of thickness. This post-treatment leads to a decrease of the percentage of porosities and to modification of the microstructure: globularized Si-rich particles are surrounded by the α-Al phase.
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<br />The method presented uses nanoindentation to determine the behavior of the different phases present in the material for future numerical simulations and a better understanding of the relation between microstructure and fatigue strength.
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<br />The Bucaille method [1] is used to determine the links between indentation curves and elastoplastic parameters. Three different pyramidal indenters are used: Berkovich, cube corner and an indenter with a centerline-to-face angle of 50 degrees. From the loading / unloading curves and after post-processing, the Young's modulus, the representative strain and the associated stress are determined. With the three different indenters and their three true stress/true strain points, a good description of the elastoplastic behavior can be defined.