Effects of micron-sized Si particles on the static and dynamic mechanical properties and fracture behavior of Al-xSi alloy sheets

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In this paper, a comprehensive analysis was conducted on the effects of micron-sized Si particles on the microstructure, static and dynamic mechanical properties, and fracture behavior of wrought Al-xSi alloy sheets. The investigation employed techniques such as optical microscope, scanning electron microscope, laser scanning confocal microscope, transmission electron microscope, tensile testing and fatigue testing. The results show that when the Si content is below 12 wt%, the size of the Si particles in the alloy sheets does not exceed 3 μm, and their quantity gradually increases with higher Si content. As the Si content increases, the grain size of the alloy sheets is refined from 63 μm to 8 μm. The alloy strength initially increases and then slightly decreases with further Si addition. while elongation exhibits a general downward trend. The tensile fracture modes of Al-(1–12 wt%) Si alloy sheets are all ductile fractures. The fatigue life of Al-xSi alloy sheets first extends and then shortens as the Si content increases. With the increase of Si content, the yield strength of the alloy sheets gradually increases from 47.6 MPa to 85.7 MPa. When the Si content is 12 wt%, the tensile strength reaches the maximum value of 185.4 MPa. With the increase of Si content, the elongation of the alloy sheet first increases slightly, reaching 35.0 %, when the Si content increases to 15 wt%, the elongation gradually decreases to 17.5 %. As the Si content increases, the fatigue life of the alloy sheets gradually extends. When the Si content reaches 12 wt%, the alloy sheet achieves its maximum fatigue life, reaching 9.97 × 105–1.97 × 10⁶ cycles, approximately 11–14 times longer than that of the Al-1 wt% Si alloy sheet. However, with a further increase in Si content to 15 wt%, the fatigue life significantly decreases to 4.08 × 10⁵–4.70 × 10⁵ cycles, shortening by approximately 59–76 %. The fatigue crack source of Al-xSi alloy sheets gradually changes from the persistent slip bands on the surface of the sheet to the large-sized Si particles on the surface of the sheet. The functional relationship between the fatigue life of Al-xSi alloy sheets as the Si content changes is established, and the fatigue life influencing factor ISi is introduced to quantitatively describe the influence of the number of micron-sized eutectic Si particles on the fatigue life or fatigue properties of the alloy sheets. This study provides important scientific insights for optimizing alloy property and meeting diverse industrial demands, thereby promoting the application and development of wrought Al-Si alloy in broader fields.