The Propagation of Slip Across Alpha/Beta Interfaces in Titanium Alloys.

摘要

The occurrence of the interface phase in (alpha + beta) titanium alloys is reviewed, and it is shown that the observed f.c.c. structure and orientation relationship may be explained either by appropriate choices of lattice shears in the beta phase followed by atomic shuffles or by application of the Bowles-Mackenzie phenomenological theory of martensite transformations. In particular, the two orientation relationships which are reported to occur between the interface phase and the lattice ae rationalised in terms of variations in the principal lattice strain which in turn arises from variations in the beta lattice parameter with solute content. Transmission electron microscopy of Ti-1.8% Mn and Ti-3.9% Mn alloys heat-treated to provide a structure consisting of Widmanstatten alpha platelets in a beta matrix and strained up to 6% in compression showed (1) that the interface phase occurred in the polycrystalline form and (2) that it appeared to act as a barrier to slip from alpha to the beta phase. However, it is considered that the effectiveness of the interface phase, gamma, in these alloys in providing a barrier to slip arises primarily from its fine polycrystalline structure.