Effect of deformation of constituent phases on mechanical properties of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy.

Deformation of constituent phases determines the mechanical properties of titanium alloys. To address this relationship, the deformation of primary α (α p ), secondary α plates (α s ) and residual β phase (β r ) in Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy was investigated based on the microstructure near fracture surface of uniaxial tensile samples. It is found that α p is elongated and α s mainly undergoes kinking deformation during tensile tests. The deformation of α p is dominated by planar slipping, the deformation of α s in colony is dominated by planar slipping and in basket weave is controlled by twin, planar slipping and dislocation tangling and the deformation of β r is controlled by dislocation tangling. In the microstructure with high volume fraction of α p (about 60%), the deformation amount of both α p and α s increases with the thickness of α s , which increases the elongation of the alloy and changes the failure modes of α p from fracture to boundary separation. In the microstructure with low volume fraction of α p (19%) and long α s , α p has large deformation amount, while α s with relative small deformation amount has large kinking region which increases the strength of the alloy. However, due to low volume fraction of α p , its contribution to the ductility of alloy is limited and thus the elongation of the alloy is relatively small. [ABSTRACT FROM AUTHOR]