Abstract: Lamellar structure produced by β annealing of titanium alloy can significantly improve the damage tolerance of the material.In this paper,the effect of β annealing parameter on microstructure and properties of Ti6Al4V alloy was analyzed and discussed through experiments.The experimental results show that with the annealing temperature increases in the range of T_β+10 ℃-T_β+50 ℃,the β grain size grows continuously.When the temperature increases to T_β+50 ℃,the strength and plasticity of the alloy decrease obviously.The holding time of β annealing is basically the same as the effect of annealing temperature on microstructure and properties.The strength and plasticity decreases but the fracture toughness increases with the holding time prolonging.The stress relief annealing increases within a certain range,the α lamellar thickness increases,the strength decreases,but the plasticity and fracture toughness increase.After β annealing,the cooling rate has remarkably influence on the microstructure and properties of the material.The greater the cooling rate is,the thickness of lamellar,grain boundary width and α lamellar thickness are obviously reduced,the strength is increased,but the plasticity is decreased.

Key words: Ti6Al4V alloy, β annealing, heat treatment, microstructure, mechanical properties