Influence of solidification rate on the low-cycle fatigue behaviour of a heat-treated AlSi7Cu3Mg aluminium alloy: an in-situ investigation [Analisi in-situ per lo studio dell'influenza della velocità di solidificazione sul comportamento a fatica a basso numero di cicli di una lega di alluminio AlSi7Cu3Mg trattata termicamente]

The present work aimed to investigate how the solidification rate influences the initiation and propagation of cracks under low-cycle fatigue conditions in a heat-treated AlSi7Cu3Mg foundry alloy. A controlled solidification process using a Bridgman furnace produced samples with Secondary Dendrite Arm Spacing (SDAS) values within two different ranges: 7-10 μm and 20-25 μm. It was observed that increasing the solidification rate resulted in a reduction in the average size of microstructural features and an increase in ultimate tensile strength. In-situ fatigue tests revealed that the two-dimensional crack path is sensitive to the solidification rate, while the use of Focused Ion Beam (FIB) thinning techniques highlighted that higher solidification speeds lead to a greater tendency for intermetallic particles to drive the crack propagation.