Effect of solution treatment on the fracture mechanisms of AlSi10Mg parts produced by Selective Laser Melting

Al alloy AlSi10Mg processed by Selective Laser Melting (SLM) displays high hardness and tensile strength due to its very fine eutectic microstructure [1]. However, as-built material exhibits low ductility which is detrimental for applications where a high resilience is needed. To overcome this issue, solution heat treatment can be applied to soften and ductilize the material [2]. The very fine eutectic microstructure then turns into a dispersion of coarse globular Si precipitates. The distribution of Si precipitates seems to play a role in the fracture mechanism in as-built as well as solutionized tempers, but this effect is not yet fully understood [1,3]. Moreover, the lack of quantitative data makes it difficult to link precisely the fracture mechanisms to specific microstructural features.
This study aims at investigating the role of the Si phase in the rupture mechanism, for both as-built and solutionized samples. It will focus more particularly on the heterogeneity of the distribution of Si precipitates where cracks are more likely to occur. Al cells size, along with the volume fraction and distribution of Si precipitates have been quantified by SEM image analysis. Al lattice parameter and Si crystallite size have been determined by X-ray diffraction/Rietveld analysis. For the image analysis, two types of specific zones have been observed i.e. the core and boundary of melt pools and Al grains, at different locations for representativity. These quantitative data have been compared with typical features observed on the fractured surface of tensile specimen.
1. D.-K. Kim et al. J. Alloys Compd. 686 (2016) 281.
2. W. Li et al., Mat. Sci. & Eng. A. 663 (2016) 116,
3. N.T. Aboulkhair et al. Mat. Sci. & Eng. A. 667 (2016) 139.