TY - JOUR AU - Segolle, Maelle AU - Santos, Jorge AU - Kasvayee, Keivan Amiri AU - Jarfors, Anders E. W. PY - 2017/03/17 Y2 - 2024/03/28 TI - Etching Method to Create Random Speckle Pattern on Semi-Solid Cast A356 Aluminium for DIC in-situ strain measurement JF - Journal of Casting & Materials Engineering JA - JCME VL - 1 IS - 1 SE - Articles DO - 10.7494/jcme.2017.1.1.33 UR - https://journals.agh.edu.pl/jcme/article/view/2204 SP - 33 AB - <p>Aluminum semi-solid casting is constantly evolving, as it offers a combination of reduced shrinkage porosity and gas<br />entrapment defects together with high productivity and an extended die-life. The relationship between the microstructure<br />and stress-strain behavior is not well-understood due to its non-conventional microstructure. In-situ tensile testing,<br />combined with optical microscope and Digital Image Correlation (DIC), has been used for local strain distribution<br />measuements in cast irons. The critical capability was an etching technique to generate a micro-scale random speckle<br />pattern with a sufficiently high speckle density to enable the sufficient spatial resolution of displacement and strain.<br />The current paper focuses on the development of a pit etching procedure for the semi-solid cast A356 aluminum alloy to<br />study local strain accommodation on the microstructure during tensile loading. The critical challenge of this procedure<br />was the generation of homogeneously distributed pits on both the primary aluminum and eutectic regions. Therefore,<br />a heated solution used for wet-etch aluminum in microfabrication was modified as well as a process adapted to generate<br />pits with suitable characteristics. In-situ tensile tests were performed attached to an optical microscope to record<br />the microstructure and displacements during loading. DIC software was used for analysis. The procedure was validated<br />through a comparison between the resulting Young´s moduls using standard tensile testing and the DIC process<br />on the speckle pattern generated. A good fit between the two methods for Young´s modulus was found. The spatial resolution<br />obtained was, however, not sufficient to fully resolve the strain gradients in the microstructure, but it did reveal<br />large strain variations in the microstructure.</p> ER -