新型β钛合金时效析出相的演变及硬化

Evolution and Hardening of Age-Precipitated Phases of New β Titanium Alloy

α相的析出形态和析出动力学对β钛合金的研究至关重要。本文利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、硬度测量及拉伸性能测试等分析手段,研究了一种自主设计的新型Ti-Al-V-Mo-Cr-Zr-Fe-Nb亚稳β钛合金时效过程中析出相的演变及硬化。研究表明:该合金经720℃固溶处理30 min,再经460℃时效3 h后产生点状α相连点成线现象,形成雪片状组织;12 h后,细小而致密的次生α相弥散分布于β基体中;至16 h后,长条状α相纵横交叉成大约60°夹角或以相互垂直的方式分布于β晶内。随着时效时间的延长,α析出相的尺寸和体积分数逐渐增加,α相体积分数增加引起的硬化和尺寸增加引起的软化相竞争,使得合金硬度和抗拉强度先增后降。该合金时效处理12 h后可获得优良的强度与塑性匹配:抗拉强度R_m=1393.6 MPa,延伸率A=12.56%,随后则出现过时效现象。

The morphology and kinetics of the precipitation of the a-phase are essential to the research of 13 titanium alloy. The evo- lution and hardening of age-precipitated phases of a self-designed Ti-AI-V-Mo-Cr-Zr-Fe-Nb metastable 13 titanium alloy were investiga- ted through optical microscope （OM）, scanning electron microscope （SEM） , transmission electron microscope （TEM）, hardness tes- ting, and tensile property test. Results showed that after solution treated at 720 ℃ for 30 min and aged at 460 ℃ for 3 h, dot a-phases pointed into a line and formed the snow-shape morphology. After aging treatment for 12 h, small and dense secondary a phases dispers- ed in the 13 matrix. After 16 h, elongated a-phases crossed at an angle of approximately 60° or distributed perpendicular to each other in the 13 intragranular. The volume fraction and dimension of a phase increased gradually with the increase of aging time. The increase of a volume fraction caused the hardening, and the increase of a dimension caused softening. A competition between the two made the hardness and tensile strength of the alloy increase firstly and then decrease with the increase of aging time. The optimal combinations of the strength and the ductility of the alloy could be obtained after aging treated for 12 h： tensile strength of 1393.6 MPa, extensibility of 12.56% , and then an over aging phenomenon appeared.