A thorough knowledge of the microstructural properties of alloys for jewelry applications is always needed both to set up the proper working processes, such as work-hardening or thermal treatments, and to understand the causes of defects that sometimes occur. By means of optical metallography, a basic knowledge of the microstructure is achieved.The present work describes the methods for the metallographic examination of platinum alloys, which need specific procedures of chemical and electrochemical etching. It will focus on different kinds of platinum alloys for jewelry after both investment casting and work hardening. Some platinum alloys used in different industrial fields will be considered as well. By comparing different microstructures, it is possible to achieve a deeper knowledge of the metallurgy of these alloys and to identify the correct working procedures, particularly the thermal treatment.Since optical metallography is just the first step toward the study of microstructures, the analytical potential of other techniques, such as the traditional scanning electron microscopy (SEM) or the transmission electron microscopy (TEM)-the latter used with specimens prepared by focused ion beam (FIB)–will be briefly described. These techniques can be used to complete the interpretation of the data given by metallographic analysis.

Author: Paolo Battaini