The effects of different heat treatment processes on the microstructure evolution and properties of Ti650 alloy plate were studied.The results show that Ti650 alloy plate is sensitive to the change of solution temperature.The primary α phase dissolution occurs with the increase of solution temperature,and the secondary α phase is smaller in size and staggered,which increases the resistance of dislocation movement,increases the strength and decreases the plasticity of the plate.Increasing aging temperature,secondary α phase changes from fine needle like to long or short layered,arranged in staggered bundles with different orientations,resulting in a significant increase in the plasticity and an appropriate decrease in strength.Under the condition of aging temperature of 700℃and aging time of 2.5～6 hours,the effect of aging time on the microstructure and properties of the plate is relatively small.The nucleation,precipitation and growth of secondary α phase are affected by different solution cooling rates.Reducing cooling rate,the secondary α phase grows from dispersed fine needle to short rod,and the strengthening effect of fine grains weakens,resulting in the decrease of room temperature strength,and the increase of plasticity.
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