Investigation of α platelet boundaries in a near-α titanium alloy

Transmission electron microscopy (TEM) of a bimodal near-α titanium alloy revealed the existence of retained β phase layers and silicide precipitates at the α platelet boundaries inside transformed β grains. The β to α phase transformation accompanied by the precipitation of silicide resulted in the formation of a large number of dislocations at α platelet boundaries. Orientation relationships between silicide, β phase and α phase were also identified. However high-resolution TEM (HRTEM) revealed crystal mismatches between these phases generating high strains at α platelet boundaries. The strengthening effects of the platelet boundaries are discussed in terms of dislocations slip across the boundaries. The mechanism that governs the β to α phase transformation is also discussed.