Mechanical Behaviour and Microstructure Evolution of Severely Deformed Two-Phase Titanium Alloys

摘要

Microstructure evolution and mechanical behavior of alpha/beta Ti-6Al-4V (VT6) and near-beta Ti-5Al-5Mo-5V-1Cr-lFe (VT22) titanium alloys during uniaxial compression at 600℃ to a high strain of 70% was studied. The plastic-flow response for both alloys is characterized by successive stages of strain hardening, flow softening, and steady-state flow. During compression the lamellae spheroidized to produce a partially globular microstructure. Globularization in VT6 is associated with the loss of the initial Burgers-type coherency between the alpha and beta phases and the subsequent individual deformation of each phase. The misorientations of boundaries increase to the high-angle range by means of the accumulation of lattice dislocations. In VT22 alloy the alpha phase evolves similar to that in VT6 alloy, while in the beta phase mainly low-angle boundaries are observed even after 70 pet. reduction.