热处理对TC4-DT钛合金棒材组织和性能的影响

研究了热处理对TC4-DT合金φ300 mm棒材显微组织、拉伸性能、断裂韧性和疲劳裂纹扩展速率的影响.结果表明:经800℃×2 hAC简单退火、α+β相区固溶+时效、β相区固溶+时效处理后的TC4-DT的显微组织分别为等轴组织、双态组织和片状组织.等轴组织具有较好的拉伸性能、低的断裂韧性和高的疲劳裂纹扩展速率:双态组织与等轴组织相比较,具有较好的拉伸性能,较高的断裂韧性和较低的疲劳裂纹扩展速率:片状组织的拉伸强度低于双态组织和等轴组织,塑性最低,断裂韧性和疲劳裂纹扩展速率与双态组织的基本相同.总体来说,TC4-DT合金经α+β相区固溶+时效、β相区固溶+时效处理后可获得R_m≥3825 Mpa,R_(P0.2)≥750 Mpa,A_5≥8%,K℃≥90 Mpa ,疲劳裂纹扩展速率小于8×10~(-6)～9×10~(-6) mm/cycle的综合性能.

Effect of Heat Treatment on Microstructure and Mechanical Properties of TC4-DT Alloy Bar

The effects of heat treatment on microstructure, tensile property, fracture toughness and fatigue crack propagation rate of 300 mm diameter bar of TC4-DT alloy were investigated. The results show that the microstructure of TCA-DT after treated by single anneal, solution treatment at α+β phase zone and aging, solution treatment at β phase and aging are respectively equiaxed structure, bimodal structure and lamellar structure. The equiaxed structure has good tensile property, low fracture toughness and high fatigue crack propagation rate. Compared with equiaxed struetttre, the bimodal structure possesses better tensile property, higher fracture toughness and lower fatigue crack propagation. The tensile strength and plasticity of the lamellar microstructure is lowest among three microstructure, the fracture toughness and fatigue crack propagation rate is similar to that ofbimodal microstructure. As a whole, after solution treatment at α+β phase zone and aging and solution treatment at β phase zone and aging, the tensile strength of TC4-DT is more than 825 Mpa, the yield strength is greater than 750 Mpa, plasticity is higher than 8%, fracture toughness is more than 90 Mpa ,and the fatigue crack popagation rate is lower than 8×10~(-6)9×10~(-6) mm/cycle.