The effects of heat-treatment, such as solution and solution-aging, on the microstructures and the phase composition for TC21 titanium alloys are studied by OM and SEM in this paper. The influence of solution temperature, solution time, cooling manners and aging on the microstructures of alloys are also discussed. The results show that the main phases are alpha and beta during heat-treated in the alpha+beta region for the alloy, otherwise, some intermetallic compounds, such as alpha(2)-Ti3Al, B-2 phase, Zr3Al, Si2Mo, etc; the solution temperature has effects on the grain size and the content of primary a phase; the solution time has no obvious effects on the microstructures; the cooling rate has effects on the transformed beta base structure; the aging also has effects on the transformed beta base structure and the secondary alpha phase.
