The nearly rapid solidification and high-temperature thermal cycles associated with laser directed energy deposition of titanium alloys using laser solid forming (LSF) lead to the formation of coarse prior β columnar grains and continuous coarse-grain-boundary α (αGB) phases, which result in anisotropic properties and poor ductility. The influence mechanisms of trace B (up to 0.3 wt. %) on the solidification, solid state transformation, and tensile properties of LSFed Ti-6Al-4V after solution and aging treatment were studied using thermodynamic calculations. With an increase in B content, the size of prior β grains decreased owing to the growth-restricting effect it caused during the solidification and the Zener pinning caused by TiB during reheat cycles and heat treatments. The continuous coarse αGB phases were almost eliminated owing to the discontinuous distribution of TiB between the dendrites, and the length and aspect ratio of intragranular α phases were gradually reduced. Moreover, both ultimate tensile strength and yield strength increased, fracture elongation decreased, strength anisotropy decreased, and elongation anisotropy initially increased and then decreased significantly. The findings in this study will promote the development of new Ti alloys befitting additive manufacturing technology.The nearly rapid solidification and high-temperature thermal cycles associated with laser directed energy deposition of titanium alloys using laser solid forming (LSF) lead to the formation of coarse prior β columnar grains and continuous coarse-grain-boundary α (αGB) phases, which result in anisotropic properties and poor ductility. The influence mechanisms of trace B (up to 0.3 wt. %) on the solidification, solid state transformation, and tensile properties of LSFed Ti-6Al-4V after solution and aging treatment were studied using thermodynamic calculations. With an increase in B content, the size of prior β grains decreased owing to the growth-restricting effect it caused during the solidification and the Zener pinning caused by TiB during reheat cycles and heat treatments. The continuous coarse αGB phases were almost eliminated owing to the discontinuous distribution of TiB between the dendrites, and the length and aspect ratio of intragranular α phases were gradually reduced. Moreover, both ultimate te...

中文翻译：

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硼对激光定向能量沉积制备Ti-6Al-4V热处理后显微组织和力学性能的影响

与使用激光固体成形 (LSF) 的钛合金激光定向能量沉积相关的几乎快速凝固和高温热循环导致形成粗大的先验 β 柱状晶粒和连续的粗晶界 α (αGB) 相，这导致各向异性特性和较差的延展性。使用热力学计算研究了微量 B（高达 0.3 wt. %）对固溶和时效处理后 LSFed Ti-6Al-4V 的凝固、固态转变和拉伸性能的影响机制。随着 B 含量的增加，由于在凝固过程中引起的生长限制效应和 TiB 在再加热循环和热处理过程中引起的齐纳钉扎效应，原 β 晶粒的尺寸减小。由于枝晶间 TiB 的不连续分布，连续粗大的 αGB 相几乎被消除，晶内 α 相的长度和纵横比逐渐减小。此外，极限抗拉强度和屈服强度均增加，断裂伸长率降低，强度各向异性降低，伸长率各向异性先升高后降低。本研究的发现将促进适用于增材制造技术的新型钛合金的开发。 与使用激光固体成形 (LSF) 的钛合金激光定向能量沉积相关的近乎快速凝固和高温热循环导致形成粗先验 β 柱状晶和连续粗晶界 α (αGB) 相，这导致各向异性特性和较差的延展性。使用热力学计算研究了微量 B（高达 0.3 wt. %）对固溶和时效处理后 LSFed Ti-6Al-4V 的凝固、固态转变和拉伸性能的影响机制。随着 B 含量的增加，由于在凝固过程中引起的生长限制效应和 TiB 在再加热循环和热处理过程中引起的齐纳钉扎效应，原 β 晶粒的尺寸减小。由于枝晶间 TiB 的不连续分布，连续粗大的 αGB 相几乎被消除，晶内 α 相的长度和纵横比逐渐减小。此外，无论是终极... 使用热力学计算研究了固溶和时效处理后 LSFed Ti-6Al-4V 的固态转变和拉伸性能。随着 B 含量的增加，由于在凝固过程中引起的生长限制效应和 TiB 在再加热循环和热处理过程中引起的齐纳钉扎作用，原 β 晶粒的尺寸减小。由于枝晶间 TiB 的不连续分布，连续粗大的 αGB 相几乎被消除，晶内 α 相的长度和纵横比逐渐减小。此外，无论是终极... 使用热力学计算研究了固溶和时效处理后 LSFed Ti-6Al-4V 的固态转变和拉伸性能。随着 B 含量的增加，由于在凝固过程中引起的生长限制效应和 TiB 在再加热循环和热处理过程中引起的齐纳钉扎效应，原 β 晶粒的尺寸减小。由于枝晶间 TiB 的不连续分布，连续粗大的 αGB 相几乎被消除，晶内 α 相的长度和纵横比逐渐减小。此外，无论是终极... 由于在凝固过程中产生的生长限制效应和在再加热循环和热处理过程中 TiB 引起的齐纳钉扎，原始 β 晶粒的尺寸减小。由于枝晶间 TiB 的不连续分布，连续粗大的 αGB 相几乎被消除，晶内 α 相的长度和纵横比逐渐减小。此外，无论是终极... 由于在凝固过程中产生的生长限制效应和在再加热循环和热处理过程中 TiB 引起的齐纳钉扎，原始 β 晶粒的尺寸减小。由于枝晶间 TiB 的不连续分布，连续粗大的 αGB 相几乎被消除，晶内 α 相的长度和纵横比逐渐减小。此外，无论是终极...