Influence of processing on microstructure and mechanical properties of (α+β) titanium alloys

The present paper tries to summarize the relationship between processing, microstructure, and mechanical properties of two-phase (α+β) titanium alloys. Although for most structural applications of titanium alloys a variety of important mechanical properties (yield stress, ductility, HCF, LCF, da/dN of micro- and macrocracks, KIC, and creep) have to be optimized or balanced, and although both processing as well as microstructure contain many variables, it can be shown that from the numerous correlation possibilities only a few underlying basic principles are really important. One of them is the relationship between cooling rate, colony size, and slip length leading directly to the advantages of a bi-modal (duplex) type of microstructure usable for most applications and involving a reproducible and insensitive processing route.