The Indentation Size Effect (ISE) of Ag–Cu Alloys

Abstract

The literature regarding the Indentation Size Effect (ISE) in metal alloys is scarce. The content of this article is the study of the relationship between the applied load and the measured values of the Vickers micro-hardness of silver and copper alloys, measured with a Hanemann hardness tester. The load values ranged between 0.09807 N (10 g) and 0.9807 N (100 g). The size and character of the ISE were evaluated using Meyer’s power law (index n), Proportional Specimen Resistance (PSR) and the Hays–Kendall method. Coins and utility objects of Central European provenance with a silver content of 50 to 99.99% were used as samples. All samples showed a reverse effect (RISE) with a value of n > 2, which is typical for plastic materials. The relatively high variability of the measured micro-hardness and consequently of the index n is related to other factors, such as the age of the sample (age hardening by the precipitation of copper), the uneven degree of deformation and microstructure. The analyzed Ag–Cu alloys show a gradual increase in the Meyer index n with the increase in the silver content, while the ISE has a reverse character throughout the range. The obtained data make it possible to determine the approximate age of artifacts from the mentioned alloys.