不同铸型对TC4钛合金的微观组织、织构和持久性的影响

Analysis of microstructure, texture and high-temperature durability of TC4 titanium alloy by different molds

摘要:

研究不同铸型成型下TC4钛合金的微观组织、织构和高温持久性能,利用光学显微镜(OM)、X射线衍射(XRD)、扫描电子显微镜(SEM)和电子背散射衍射(EBSD)等观察和分析TC4钛合金的显微组织与持久性断裂行为。结果表明：不同铸型工艺TC4钛合金的物相均为α相、β相和ω相组成,其中主要物相为α相(90%左右)。与石墨型相比,陶瓷型有利于β→α相变,α相高出5.3%,晶粒平均直径大(d_mean=37.021μm),晶界较少,晶粒均匀相对稳定,当α相比例增大时,材料强度减小,塑性升高。同时陶瓷型织构强度高,取向明显,织构类型为{11-20}<1-100>,与Y方向呈现约45°的夹角,进一步验证了试样在(101)、(002)、(101)峰强增加的原因,与织构的形成有关；陶瓷型试样的高温持久性优于石墨型,在温度(400℃、430℃、460℃)下,持久性应力断裂寿命分别提高了1.174%、15.401、6.998%,均为韧性断裂,其微观形貌为韧窝花样。此外,温度直接影响TC4钛合金的持久寿命,随着温度升高,TC4钛合金的应力断裂寿命逐渐降低。

Abstract:

Investigate the microstructure, texture and high-temperature endurance properties of TC4 titanium alloys under different molds. the optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron back scattering diffraction (EBSD) were used to observe and analyze the microstructure and persistent fracture behavior of TC4 titanium alloy.The results show that the phases of TC4 titanium alloy by different molds are all composed of α phase, β phase and ω phase, and the main phase is α phase (about 90%). Compared with the graphite type, the ceramic type is favorable for the β→α phase transition, the α phase is 5.3% higher, the average grain size is large (dmean = 37.021μm), the grain boundaries are less, and the grains are relatively uniform and relatively stable. When it is large, the material strength decreases and the plasticity increases. Simultaneously, the ceramic-type texture has high strength and obvious orientation. The texture type is {11-20} <1-100>, and the angle with the Y direction is about 45°, it further verified that the samples are in (101), (002),(101) .The reason for the increase in peak intensity is related to the formation of texture，The high temperature durability of ceramic samples is better than that of graphite. At the temperature (400℃，430℃，460℃), the persistent stress fracture life has increased by 1.174%, 15.401, 6.998%, all of which are ductile fracture. Appearance is a dimple pattern. In addition, temperature directly affects the long-term life of TC4 titanium alloy. as the temperature increases, the stress fracture life of TC4 titanium alloy gradually decreases.