Study on precipitates behavior during heat treatment in Ti-B19 titanium alloy

The phase transformation and microstructure evolution of near β Ti-B19 alloy during solution and aging treatment were studied systematically by using the optical microscopy (OM), x-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TKM). The results sHowed that equiaxed β structure consisting of metastable β phase and silicide phase formed in the sample after solution treatment. When the samples were aged between 300°C and 150°C the ellipsoid ω phase appeared firstly in β matrix,and gradually transformed into equilibrium a phase, acicular α could precipitate directly from β matrix besides particle a precipitation from α phase through transition of ω phase. Upon increasing the aging temperature to 5OO-650°C ,acicular α phase precipitated directly in β grain boundaries. Linear α phase consisting of particle α phase was found in the samples at the ageing temperature above 500°C. For the samples aged at 700-750°C, the plate-like α phase precipitated along β grain boundaries.