On the cyclic deformation behavior and correlated damage mechanism of selective laser melted AlSi10Mg alloy holding different initial microstructures

Abstract

The present work deals with the cyclic deformation behavior of AlSi10Mg alloy fabricated through selective laser melting. Toward this end, the printed material was heat treated and was tested through strain-controlled push–pull fatigue under different strain amplitudes. The highest strengths were recorded for the direct aged, as-built and solutionized microstructures, respectively. The directly aged microstructure was characterized by the transformation of the columnar solidified structure into the equiaxed one and formation of the nano-Si precipitates. This was led to the best fatigue performance where an outstanding balance between the fatigue life and strength level was recorded. The low aspect ratio of the melt pools intensified the Marangoni effect, therefore, caused concentration of the material flow on the wetting side. This led to crack initiation and propagation at the end of the melt pools and formation of balling defects. Balling defect was characterized as the initiation site in the case of as-built and directly aged specimens, the cone-like geometry of which resulted in crack path deflection and a better fatigue performance. For solution treated microstructure, the melt pools were dissolved and the lack of fusion holding a critical size and located close to the surface, was characterized as the main crack initiation site.