We present a case study – showing the benefits of using multiple microscopic techniques as part of a single workflow, operating at different length scales to investigate the failure of a component and determine the secondary effects on the structure and microstructure.
A 7075 aluminium alloy component had failed. A series of investigations were carried out at various length scales to determine the extent of the damage and confirm the failure mechanism. The failed section of the component was scanned in 3D using X-ray computed tomography to obtain a full 3D map of the interior and exterior. The interior and exterior dimensions were measured in key areas and the location of the largest crack was determined. Additional surface scans were carried out using digital light microscopy and extended depth of field scans to examine threaded regions. Using scanning electron microscopy and examination of cross-sections by light and scanning electron microscopy the thickness of the anodization/coating layer was verified, along with detection of cracking in the layer in several regions.
Light microscopy of cross-sections also verified that secondary cracking did not penetrate deeper than 200µm into the main body of the component. The fracture faces were examined using scanning electron microscopy, verifying that the largest crack was surface-breaking with characteristic fatigue striations radiating outwards
By combining and correlating information from all of these different microscopy techniques, it was concluded that the component had failed by fatigue likely initiating from the 90° angle corner, but with minimal damage/deformation to the remainder of the component directly outside of the failed region.