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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 precipitation morphology and precipitation kinetics of α phase are crucial for the study of β-titanium alloy. In this paper, a new type of Ti-Al-V-Mo-Cr-Zr alloy designed by ourselves was studied by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness measurement and tensile test. Evolution and Hardening of Precipitated Phase in Aging Process of Fe-Nb Metastable β-Ti Alloy. The results show that the microstructure of the alloy is formed after the solution treatment at 720 ℃ for 30 min and then after aging at 460 ℃ for 3 h. The fine and compact secondary α phase Diffusely distributed in the β matrix. After 16 h, the elongated α-phase crosswise and horizontally intersects at an angle of about 60 ° or is distributed in the β-crystal in a mutually perpendicular manner. With the extension of the aging time, the size and volume fraction of α precipitates increased gradually, and the softening phase caused by the increase of α phase volume fraction increased the hardness and tensile strength of the alloy first and then decreased. After aging for 12 h, the alloy has excellent strength and plasticity matching: the tensile strength R_m = 1393.6 MPa and the elongation A = 12.56%, then the over-aged phenomenon appears.