论文摘要
本文采用非自耗真空氩弧熔炼炉熔炼合金,研究了冷却速度对Ti-48Al、Ti-48Al-0.2B、Ti-52Al、Ti-52Al-0.2B合金显微组织的影响;利用六面顶压机分别在2GPa和4GPa高压下制备Ti-48Al凝固试样;利用X射线衍射对不同冷却速度下的TiAl金属间化合物及高压下凝固的TiAl金属间化合物相组成进行了分析;采用光学显微镜、扫描电子显微镜、能谱分析仪等分析测试手段分别对常压、高压下合金凝固组织形貌进行了观察。X射线衍射分析表明,随着冷却速度的增加,Ti-48Al合金中γ相晶格参数a有减小的趋势,而c值的变化并无规律;使用铜和石墨模具吸铸的Ti-48Al和Ti-48Al0.2B合金试样,其原始α晶粒特别细小,块状转变完全,无α2/γ片层组织或α2单相组织,吸铸后只产生γ单相。随着冷却速度的增加,Ti-52Al和Ti-52Al-0.2B合金晶粒尺寸均有减小的趋势,微量B元素的加入致使片层组织间距变小,且B的细化效果减弱。高压下凝固的Ti-48Al合金由α2-Ti3Al和γ-TiAl相组成,随着凝固压力的增大,α2-Ti3Al相含量及片层组织均增多,偏析γ-TiAl相减少,且片层组织中Al含量升高。在不同压力下凝固时,圆形试样边缘的组织和心部的组织均有较大的差异,2GPa下凝固时,边缘部位和心部均为双态组织,但心部偏析γ-TiAl相较边缘部位多;而4GPa下凝固时,试样边缘组织为全片层状组织,心部为双态组织。文中最后讨论了压力对Ti-Al合金偏析的影响,随着压力的增大溶质偏析变小。
论文目录
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