高强TB9钛合金次生α相析出行为及力学性能

Precipitation behavior of secondaryαphase and mechanical properties of high strength TB9 titanium alloy

研究单/双重时效热处理对TB9合金次生α相形貌及力学性能的影响规律。借助XRD分析合金相组成,采用光学显微镜和扫描电子显微镜观察显微组织,着重分析微观组织形貌随时效温度变化的演变特征,测试室温拉伸性能和断裂韧度。研究结果表明:单重时效时,晶粒内次生α相呈锯齿状和片层状析出,随着时效温度升高,α相尺寸增大,片层状α相含量增加;430℃时效时,合金强度较低,塑性较好,在470℃时效时合金强度最高;随时效温度的提高,强度先增大后维持在同一强度水平。双重时效时,晶粒内次生α相主要呈锯齿状析出,随时效温度升高,α相尺寸增大,抗拉强度先升高后降低,最高可达1542 MPa,且塑性变化较小。双重时效下合金的抗拉强度较单重时效大幅提高,这主要是由于晶界附近第二相析出强化和晶内锯齿结构α相的共同作用。

The precipitation behavior of secondaryαphase and mechanical properties of high strength TB9 titanium alloy were investigated during single aging and duplex aging.The alloy phase constitution was analyzed by XRD,and the microstructure was observed by optical microscopy and scanning electron microscopy.The evolution characteristics of the microstructure with aging temperature were mainly analyzed.The room temperature tensile properties and fracture toughness were tested.The research results indicate that during single aging,secondaryαphase exhibits serrated and layered precipitation.With increasing aging temperature,the size ofαphase increases,and the content of layeredαphase increases.The strength at 430℃aging is lower and the plasticity is higher.The strength at 470℃aging is the highest.With increasing aging temperature,the strength first increases and then maintains at the similar level.During duplex aging,most of secondaryαphases precipitate in a serrated shape within the grains.With increasing aging temperature,the size ofαphase increases,the tensile strength first increases and then decreases,reaching a maximum of 1542 MPa.The tensile strength of duplex aging is significantly higher than that of single aging,which is mainly due to the combined strengthening effect of second phases near grain boundaries and intragranularαphases with serrated shape.