具有α″马氏体组织的Ti-3Al-4.5V-5Mo钛合金拉伸变形行为

研究了具有α″马氏体组织的Ti-3Al-4.5V-5Mo钛合金拉伸变形行为。结果表明:具有α″马氏体组织的Ti-3Al-4.5V-5Mo钛合金具有较低的屈服强度和良好的塑性。在拉伸变形时,α″马氏体晶格重新取向:[010]α″方向平行于拉伸轴线,[100]α″方向垂直于拉伸轴线;b/3a增加,产生了斜方结构α″向密排六方结构α′相的转变。应变产生的α″→α′马氏体转变为位移型无扩散二级相变,热力学计算表明,在拉伸变形条件下发生α″→α′马氏体转变时,体系的自由能降低。

高氢对Ti600合金显微结构的影响

利用XRD、OM、SEM、TEM分析方法研究了Ti600合金在高氢含量下微观组织的变化、相的析出行为等,并分析了高氢含量下Ti600合金除氢后的显微组织。结果表明,置氢处理后Ti600合金的显微组织结构发生了明显变化,形成具有不同取向的、平行的细片层组织;经XRD、TEM标定,析出的细片层组织为氢化物相、α相和α″马氏体。除氢后,合金中的相与原始合金一致,但等轴α相转变为平行排列的短片状α,并形成取向不同的集束。

Microstructures of TC21 alloys after hydrogenation and dehydrogenation

Microstructural evolution and phase transformation of hydrogenated and dehydrogenated TC21 alloys were investigated by optical microscopy （OM）, X-ray diffraction （XRD） and transmission electron microscopy （TEM）. XRD peaks ofαandβphases after hydrogenation shifted to low angle because of lattice expansion with the solution of hydrogen atoms. Microstructure of TC21 alloy after hydrogenation changed apparently. Compared to the as-received one, the contrasts of equiaxedαphase and transformedβphase under optical microscope were reversed. In addition, XRD and TEM analyses revealed that hydrides and α′ martensite precipitated fromαandβphases. Bulk of twins and some Ti3Al particles were observed in hydrogenated TC21 alloy, which means that hydrogen led to the redistribution of alloying elements inαandβphase. After dehydrogenation, the microstructure of TC21 alloy was similar to that of the as-received one, which consisted ofαandβphases.

热处理工艺对Ti6246钛合金组织与力学性能的影响

研究了热处理温度和冷却方式对Ti6246合金显微组织、相组成以及室温拉伸性能的影响。结果表明:固溶热处理后合金的相组成主要与冷却方式有关。在β单相区及(α+β)两相区固溶后水冷,β相均转化为α′′马氏体和少量亚稳β相。空冷组织中的β相转变为含有少量次生α相的β转变组织,随着热处理温度的提高次生α相的含量逐渐增加,尺寸也逐渐增大。时效后组织中的亚稳相发生分解,析出细小的次生α相。固溶后水冷试样的拉伸曲线上出现"双屈服"现象,且随着固溶温度的提高合金第一屈服点逐渐升高。水淬和空冷合金试样在595℃/8 h时效后其室温拉伸强度提高,延伸率及断面收缩率降低,水淬试样室温拉伸性能的变化更大。固溶后空冷且在595℃时效处理的合金,其室温拉伸性能可达到较好的强塑性匹配。