How can fracture mechanics and failure analysis assist in solving mysteries of ancient metal artifacts?

Micro and Nanoscale Structures and Corrosion Patterns in Brass: The Case Study of Ancient Roman Orichalcum Coins

“…Micrographic investigations on other ancient alloys proved that the dendritic arms in cast objects were preferentially corroded, compared to the inter-dendritic areas, which were preferentially preserved [46]. Therefore, it could be suggested that the strain lines here observed represented preferential areas of corrosion in orichalcum samples, like the dendritic structures for other copperbased alloys [7].…”

“…The strain lines as evidence of plastic deformation shown by SEM and FESEM imaging indicated heavy cold-working during the minting process, where the metal planchet was hammered between two dies below its recrystallization temperature. This hammering, required for coinage, caused the slip of crystal planes and, as a consequence, a series of parallel movements, which resulted in fine lines [7,46]. Such slip usually occurs along the line of the maximum shearing stress [52].…”

“…According to Sieradzki et al [53], the trans-granular stress corrosion could be correlated with the dislocated structures of deformed alloys when in contact with basic solutions. Other authors [7,54] report that the local strain due to cold working seems to have a key role in the acceleration of stress corrosion cracking, deforming grain boundaries and inducing corrosion.…”

“…The negative impact of corrosion on the conservation of private and museum collections justifies great technological and scientific endeavour in the study of metal deterioration. [7][8][9][10]. In this context, significant efforts have been made to understand, predict and prevent corrosion [11][12][13].…”

“…Indeed, the study of ancient alloys permits the evaluation of metal behaviours and corrosive processes in different burial environments [8,[16][17][18][19]. Experimental studies on the long-term corrosion mechanism of alloys at the micro and nanoscales, and the distribution of damage, represent one of the major challenges that must be addressed to protect archaeological objects [7].…”