Thermo-Mechanically Assisted Grain Growth in Ti6Al4V Fabricated Using the Powder Bed Additive Manufacturing During High-Temperature Mechanical Testing
Thermo-Mechanically Assisted Grain Growth in Ti6Al4V Fabricated Using the Powder Bed Additive Manufacturing During High-Temperature Mechanical Testing
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DOI：
10.1007/s11661-023-06989-y
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发表时间：
2023-02
期刊：
影响因子：
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通讯作者：
L. Ladani;J. Razmi;Md Jamal Mian
中科院分区：
文献类型：
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作者：
L. Ladani;J. Razmi;Md Jamal Mian
金属合金的高温力学行为以及导致这种行为的微观结构变化是许多行业特别是高温应用领域的重要研究领域。在金属粉末床熔融添加剂制造过程中，由于热梯度和冷却速度的变化，以及随后在零件在其特定应用中所经历的不同热机械载荷期间发生的颗粒转变，也会影响其在室温和高温下的力学性能。本研究旨在深入分析和了解电子束粉床熔化Ti6Al4V合金在高温机械载荷作用下，由于相互作用机制，其组织结构的变化规律。对600℃以下不同成型取向的EB-PBF零件进行了力学测试，并对高温力学测试前后的样品进行了电子背散射(EBSD)显微组织分析，以了解温度和机械载荷对变形机制激活的交互影响。EBSD分析表明，颗粒尺寸和颗粒取向都取决于构建取向。高温力学性能测试表明，材料在400℃~600℃范围内表现出软化行为。此外，还观察到了各向异性行为，这与β相的体积比以及各向异性颗粒的形成有关。在较高的试验温度下观察到了一定的晶粒粗化现象。随着温度的变化，取向不良角和某些择优取向的额外变化表明几何变形机制的激活。
High-temperature mechanical behaviors of metal alloys and the underlying microstructural variations responsible for such behaviors are important areas of interest for many industries particularly in their high-temperature applications. Transformation of grains which occur both during metal powder bed fusion additive manufacturing processes due to variation of thermal gradient and cooling rates, and afterward during different thermomechanical loads that parts experience in their specific applications, could also impact its mechanical properties both at room and high temperatures. This study focuses on in-depth analysis and understanding of how the grain structures of electron beam powder bed fusion (EB-PBF) Ti6Al4V alloy changes during high-temperature mechanical load, due to the interacting mechanisms. Mechanical testing is conducted for EB-PBF parts made at different build orientations up to 600 °C. Microstructural analysis using electron backscattered diffraction (EBSD) is conducted on samples before and after high-temperature mechanical testing to understand the interacting impact that temperature and mechanical load have on the activation of deformation mechanisms. EBSD analysis showed both grain size and grain orientation to be dependent on the build orientation. Mechanical testing at high temperature showed softening behavior especially from 400 °C to 600 °C temperature. Additionally, anisotropic behavior was observed which is associated with volume ratio of β phase as well as the anisotropic grain formation. Some grain coarsening was observed at higher test temperatures. Additional changes in misorientation angle and certain preferred grain orientation that varies with temperature signifies activation of geometric deformation mechanism.