MICROSTRUCTURAL INTERACTIONS DURING FLOW OF 2-PHASE TITANIUM-ALLOYS

To describe the stress-strain behaviour of two-phase alloys in many cases a very simple law, the so-called rule of mixture, has been employed: sigma = SIGMAsigma(i)f(i) and epsilon = SIGMAepsilon(i)f(i) where i is a phase index and f the volume fraction. The paper gives a short review of applications and adaptation of this rule to experimental observations on titanium alloys. The problem with this approach and its modifications is that it does not consider adequately the great variety of possible microstructural interaction mechanisms, which depend on factors such as phase morphology, crystallographic relationship between different phases, work hardening characteristics etc. The importance of these aspects for multiphase behaviour will be demonstrated by two examples, namely: strength and flow in a system with two ductile components; and flow and work hardening of a ductile matrix with hard lamellar inclusions. This view shows that for an adequate description of a given material an individual adaptation to the particular ruling mechanisms, which vary from case to case, is necessary.