In Part I, the effect of alloying on the various properties of precious metals for jewelry and their alloys was examined and the influence of working and annealing on properties was also explained. In Part II the importance of alloy microstructure, particularly grain size, and the way it can be influenced and controlled through casting, working and thermal treatments was examined. We noted that properties, alloy composition and microstructure are all interrelated. In Part III, we examine some of the defect issues, particularly cracking, that can lead to problems in both manufacture and later in service with the customer. The common causes of such defects and the steps that can be taken to minimize their occurrence are reviewed. These include poor quality start materials, bad melting practices, poor ingot or material working practice, incorrect annealing and stress corrosion cracking.

Author(s): Dr. Christopher W. Corti