Ti-3Al-8V-6Cr-4Mo-4Zr合金低周疲劳行为研究
发布时间：2018-11-05 21:09
【摘要】：钛合金是20世纪50年代开发的一种轻质合金,因其在力学性能、耐蚀性能、耐热性能等方面的优异表现,逐渐成为工程应用上重要的结构材料。其中,亚稳β钛合金以其较高的强度、韧性以及优良的冷加工性能,近年来日益受到人们的关注。作为一种结构材料,亚稳β钛合金常被应用于机械结构关键部位,疲劳失效是其主要的破坏形式之一。然而,针对亚稳β钛合金的研究主要集中于显微组织、基本力学性能等方面,关于Ti-3Al-8V-6Cr-4Mo-4Zr合金的疲劳性能以及疲劳变形中显微结构变化的研究很少见。本论文采用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)等手段对不同热处理状态下Ti-3Al-8V-6Cr-4Mo-4Zr合金的显微组织、拉伸性能以及低周疲劳性能进行了系统的研究,分析了热处理工艺对合金微观组织的影响,讨论了不同状态下合金拉伸、疲劳变形行为及损伤机制。研究发现:热轧态Ti-3Al-8V-6Cr-4Mo-4Zr合金的显微组织由原始等轴β晶粒和球状初生α相组成,800℃/30min固溶处理后,初生α相变小并逐渐转变成β相。800℃/30min+500℃/4h时效处理后初生α相全部转变成β相,且有少量次生球状α相从β基体中析出;当时效时间增至12h时,α相析出的数量明显增加,且转变为针棒状,同时β晶粒得到细化。拉伸试验结果表明,该合金力学性能中的抗拉强度在经过时效热处理后明显高于热轧态和固溶态合金。经过800℃/30min+500℃/12h处理以后,合金的硬度及抗拉强度达到最大值,其延伸率和断面收缩率并没有明显的降低。断口分析表明,热轧态及固溶态合金的断口形貌为典型的韧性断裂;而时效后的合金在塑性变形过程中表现为脆性和韧性相结合的混合型断裂模式。在外加总应变控制的低周疲劳加载条件下,不同状态的该合金在0.4%~0.8%的外加总应变幅下,均表现出稳定的循环应力响应行为;在1.0%的外加总应变幅下,热轧态合金则表现为先循环软化,后循环稳定,而时效态合金表现为循环稳定;在1.2%~1.4%的外加总应变幅下,三种状态的合金均表现为循环软化。时效处理状态下,经500℃/12h时效处理的合金表现出了最高的循环变形抗力与较高的低周疲劳寿命。不同热处理状态下的合金的塑性应变幅、弹性应变幅与载荷反向周次之间均呈线性关系,可分别用Coffin-Manson公式和Basquin公式来描述。不同热处理状态下合金的循环应力幅值(35)σ/2与塑性应变幅值(35)?p/2之间也均呈线性关系。疲劳断口观察表明,在外加总应变控制的低周疲劳加载条件下,不同热处理状态下合金的疲劳裂纹均以穿晶方式萌生于疲劳试样表面,并以穿晶方式扩展。
[Abstract]:Titanium alloy is a kind of light alloy developed in 1950s. Because of its excellent performance in mechanical property, corrosion resistance and heat resistance, titanium alloy has gradually become an important structural material in engineering application. Among them, metastable 尾-titanium alloys have attracted more and more attention in recent years because of their high strength, toughness and excellent cold working properties. As a kind of structural material, metastable 尾 -titanium alloy is often applied to the key parts of mechanical structure, and fatigue failure is one of its main failure forms. However, the study of metastable 尾 -titanium alloys is mainly focused on the microstructure, basic mechanical properties and so on. The study on the fatigue properties and microstructure changes of Ti-3Al-8V-6Cr-4Mo-4Zr alloys during fatigue deformation is rare. In this paper, (OM), scanning electron microscope (OM),) and (SEM), transmission electron microscope (TEM) were used to study the microstructure of Ti-3Al-8V-6Cr-4Mo-4Zr alloy under different heat treatment conditions. The tensile properties and low cycle fatigue properties were studied systematically. The effect of heat treatment on the microstructure of the alloy was analyzed. The tensile, fatigue deformation behavior and damage mechanism of the alloy under different states were discussed. It is found that the microstructure of hot-rolled Ti-3Al-8V-6Cr-4Mo-4Zr alloy is composed of original equiaxed 尾 grains and spherical primary 伪 phase, and is treated at 800 鈩，
本文编号：2313470
[Abstract]:Titanium alloy is a kind of light alloy developed in 1950s. Because of its excellent performance in mechanical property, corrosion resistance and heat resistance, titanium alloy has gradually become an important structural material in engineering application. Among them, metastable 尾-titanium alloys have attracted more and more attention in recent years because of their high strength, toughness and excellent cold working properties. As a kind of structural material, metastable 尾 -titanium alloy is often applied to the key parts of mechanical structure, and fatigue failure is one of its main failure forms. However, the study of metastable 尾 -titanium alloys is mainly focused on the microstructure, basic mechanical properties and so on. The study on the fatigue properties and microstructure changes of Ti-3Al-8V-6Cr-4Mo-4Zr alloys during fatigue deformation is rare. In this paper, (OM), scanning electron microscope (OM),) and (SEM), transmission electron microscope (TEM) were used to study the microstructure of Ti-3Al-8V-6Cr-4Mo-4Zr alloy under different heat treatment conditions. The tensile properties and low cycle fatigue properties were studied systematically. The effect of heat treatment on the microstructure of the alloy was analyzed. The tensile, fatigue deformation behavior and damage mechanism of the alloy under different states were discussed. It is found that the microstructure of hot-rolled Ti-3Al-8V-6Cr-4Mo-4Zr alloy is composed of original equiaxed 尾 grains and spherical primary 伪 phase, and is treated at 800 鈩，
本文编号：2313470
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