HOT DEFORMATION BEHAVIOR OF NEAR-α Ti-Fe ALLOY IN (α plus β) TWO-PHASE REGION WITH DIFFERENT Fe CONTENT

In the present study, microstructure evolution of Ti-Fe alloys with different Fe content between 0.2-1.5mass% during hot deformation in (alpha+beta) two-phase region is studied with focusing on effect of phase volume fraction at different deformation temperatures and strain rates. Hot deformation was conducted on the specimens quenched after beta solutionizing at 1173K for 1.2ks at 1108, 1073 and 948K, by uniaxial compression by 50% at various strain rates ranged from 1 to 10(-4) s(-1). Initial structures are (alpha+beta) lamellar structures of fine interlamellar spacing and colony sizes. Increase in Fe content results in increasing the fraction of the beta phase at the given deformation temperature Either colony size or interlamellar spacing is coarser at higher temperatures. At the higher deformation temperature where beta phase fraction is larger, dynamic recovery of beta phase is a major deformation mechanism while at a lower temperature, i.e, a higher alpha fraction, dynamic recrystallization of a phase occurs predominantly. It is concluded that critical strain needed for occurrence of dynamic recrystallization is decreased by increasing fraction of the alpha phase at the same deformation temperature, i e., by decreasing Fe content. Furthermore, by increasing strain rate grain size of the recrystallized alpha is decreased