TC4-DT钛合金热机械处理后的组织特征和力学性能

研究热机械处理（两相区变形加普通退火、双重退火、固溶时效以及三重退火）对 TC4-DT 钛合金组织和力学性能的影响。结果表明，热机械处理对显微组织参数影响显著，随着退火和时效温度的升高及冷却速度的降低，初生α相的体积分数和原始β晶粒的尺寸降低，而晶界α和次生α相的宽度却升高。由于固溶时效处理获得了大量的β转变组织和细小的晶界α相和次生α相，合金强度最高，但伸长率不及其它条件的，其断裂强度、屈服强度、伸长率和断面收缩率分别为1100 MPa、1030 MPa、13%和53%，双重退火获得了良好的强度和塑性匹配，合金力学性能分别为940 MPa、887.5 MPa、15%和51%。组织参数和性能的关系表明，随着β转变组织的增多和原始β晶粒尺寸的增大，材料的强度和断面收缩率升高，而晶界α相和二次α相的宽度对力学性能的影响却呈相反趋势。此外，晶界α相含量的减少和原始β晶粒尺寸的降低有助于塑性的提高。

Microstructure characterization and mechanical properties of TC4-DT titanium alloy after thermomechanical treatment

Influence of thermomechanical treatments （mill annealing, duplex annealing, solution treatment plus aging and triple annealing） on microstructures and mechanical properties of TC4-DT titanium alloy was investigated. Results showed that thermomechanical treatments had a significant influence on the microstructure parameters and higher annealing and aging temperature and lower cooling rate led to the decrease of the volume fraction of primaryαand the size of prior-βand the increase of the width of grain boundary αand secondary α. The highest strength was obtained by solution treatment and aging due to a large amount of transformedβand finer grain boundaryαand secondaryαat the expense of slight decrease of elongation and the ultimate strength, yield strength, elongation, reduction of area were 1100 MPa, 1030 MPa, 13%and 53%separately. A good combination of strength and ductility has been obtained by duplex annealing with the above values 940 MPa, 887.5 MPa, 15%and 51%respectively. Analysis between microstructure parameters and tensile properties showed that with the volume fraction of transformedβphase and the prior-βgrain size increasing, the ultimate strength, yield strength and reduction of area increased, but the elongation decreased. While the width of grain boundary α and secondary α showed a contrary effect on the tensile properties. Elimination of grain boundaryαas well as small prior-βgrain size can also improve ductility.