The correlation of c-to-a axial ratio and slip activity of martensite including microstructures during thermomechanical processing of Ti–6Al–4V alloy

Abstract

This study deals with the correlation of the “c-to-a” ratio of ά-martensite and the activity of basal/secondary slip systems during thermomechanical processing of Ti–6Al–4V alloy. Two martensite including microstructures (dual phase α+ά and full ά martensite) were prepared and deformed in tensile mode at 300 °C and 600 °C. The presence of ά-martensite caused the reduction of the c-to-a ratios compared to that of the as-received α+β starting microstructure. Owing to the elemental partitioning, the amount of axial ratio reduction was considerable in the case of dual phase α+ά microstructure and caused activation of pyramidal slip during low temperature tensile deformation. This promoted the wavy configuration of dislocation and led to intensified substructure development. At higher deformation temperature, where the martensite phase was almost completely converted into the fine α+β phase through reverse transformation, the c-to-a ratio reached ∼1.599 increasing the critical resolved shear stress of the secondary slip systems.

Keywords

• Titanium alloys
• c-to-a ratio
• Slip activity
• Phase transformation
• Thermomechanical processing
• Elemental partitioning