In Part I last year, the effect of alloying on the various properties of the jewelry precious metals and their alloys was examined and related to microstructure through an understanding of phase diagrams – the metallurgist's "road maps" of alloying behaviour. The influence of working and annealing on properties was also explained. We noted that properties, alloy composition and microstructure are all interrelated. In this second part, we focus more on the alloy macro- and microstructures and how they are affected by its processing history - solidification conditions, working and thermal treatments - which, in turn, influences the final properties. We look at metal integrity, microstructure development and defect formation during casting and working, and how microstructure is important to both manufacturing and service performance.

Author: Dr. Christopher W. Corti