Precipitation

Abstract

The phenomena described in the three previous chapters are related to the decomposition of austenite and apart from steels, the mechanisms involved are encountered in only a limited number of alloy systems. For example, martensitic transformations also exist in titanium alloys. In contrast, precipitation is extremely common in many binary or multicomponent materials. It is a process whereby an additional phase is formed from a supersaturated solution. Indeed, the term precipitation is familiar even to non specialists, being used among other things to describe rain, which can he promoted by the use of nucleants, as in metallurgy. Although the examples given are chosen among iron-lase materials, the principles outlined in the present chapter can be applied to most alloy systems, including those based on lead, nickel copper, aluminium, etc.