Microstructure and texture evolution during β extrusion of boron modified Ti-6A1-4V alloy

摘要

Boron addition to conventional titanium alloys below the eutectic limit refines the cast microstructure and improves mechanical properties. The present work explores the influence of hypoeutectic boron addition on the microstructure and texture evolution in Ti-6A1-4V alloy under β extrusion. The p extruded microstructure of Ti-6A1-4V is characterized by shear bands parallel to the extrusion direction. In contrast, the extruded Ti-6A1-4V-0.l B alloy shows a regular p worked microstructure consisting of fine prior P grains and acicular a-lamellae with no signs of the microstructural instability. Crystallographic texture after extrusion was almost identical for the two alloys indicating the similarity in their transformation behavior, which is attributed to complete dynamic recrystallization during β processing. Microstructural features as well as crystallographic texture indicate dominant grain boundary related deformation processes for the boron modified alloy that leads to homogeneous deformation without instability formation. The absence of shear bands has significant technological importance as far as the secondary processing of boron added alloys in ( α + β)-phase field are concerned.