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Metallurgical characterisation of a historical metal tie-rod from Milan Cathedral
Highlights The metallurgical features of a hand-made tie were studied to infer the causes of failure. The material was found to be extremely heterogeneous in terms of matrix, inclusions and defects. Metallurgical evidence suggests that failure occurred along forged welds. More ductile behaviour is associated with a mainly ferritic matrix with iron-rich bulky-shape dendritic slag inclusions. Sudden variation of microstructure due to the forged weld can be seen across the visible crack.
Abstract One tie-rod from Milan Cathedral (15th century) recently broke in a defective cross-section. In order to infer the causes of failure, a metallurgical characterisation was performed, the results of which are discussed here. First, a visual inspection of the specimen was performed. Next, the fracture surface was analysed using a Scanning Electron Microscope (SEM) combined with Energy Dispersive X-Ray Spectrometry (EDXS) to detect the failure modes involved. A cross-section close to the failure surface was investigated by means of Stereoscopy, Light Optical Microscopy (LOM), SEM and EDXS in order to identify the microstructural compounds and characterise the slag inclusions. Vickers and Rockwell hardness tests were also carried out to correlate microstructural observations with mechanical properties. A strong relationship between failure and defects due to forging was observed, which is a particularly noteworthy result with regard to the representativeness of laboratory tests and the viability of in-situ inspection.
Metallurgical characterisation of a historical metal tie-rod from Milan Cathedral
Highlights The metallurgical features of a hand-made tie were studied to infer the causes of failure. The material was found to be extremely heterogeneous in terms of matrix, inclusions and defects. Metallurgical evidence suggests that failure occurred along forged welds. More ductile behaviour is associated with a mainly ferritic matrix with iron-rich bulky-shape dendritic slag inclusions. Sudden variation of microstructure due to the forged weld can be seen across the visible crack.
Abstract One tie-rod from Milan Cathedral (15th century) recently broke in a defective cross-section. In order to infer the causes of failure, a metallurgical characterisation was performed, the results of which are discussed here. First, a visual inspection of the specimen was performed. Next, the fracture surface was analysed using a Scanning Electron Microscope (SEM) combined with Energy Dispersive X-Ray Spectrometry (EDXS) to detect the failure modes involved. A cross-section close to the failure surface was investigated by means of Stereoscopy, Light Optical Microscopy (LOM), SEM and EDXS in order to identify the microstructural compounds and characterise the slag inclusions. Vickers and Rockwell hardness tests were also carried out to correlate microstructural observations with mechanical properties. A strong relationship between failure and defects due to forging was observed, which is a particularly noteworthy result with regard to the representativeness of laboratory tests and the viability of in-situ inspection.
Metallurgical characterisation of a historical metal tie-rod from Milan Cathedral
Bellanova, Mariagrazia (author) / Baggioli, Andrea (author) / Rivolta, Barbara (author) / Felicetti, Roberto (author)
Construction and Building Materials ; 226 ; 888-898
2019-07-22
11 pages
Article (Journal)
Electronic Resource
English
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