Abstract In this work, titanium blocks of Ti-5Al-5Mo-5V-3Cr (Ti-5553) have been Laser Metal Deposited (LMD) on forged substrate of the same alloy under varying laser power and powder feed rates. The microstructure has been characterized using optical microscopy, scanning electron microscopy and Electron backscatter diffraction (EBSD) techniques. Microstructure was predominantly large columnar β-grains aligned with the build direction interspersed with fine equiaxed β-grains. Increase in the powder feed rate was found to reduce the average β-grain size and promoted clusters of fine grains to be retained during the deposition of subsequent layers. Increase in the laser power also reduced the average β grain size and promoted greater nano-scaled α precipitates at the substrate interface and initial deposited layers which significantly increased the microhardness in this area. Dendrites exist due to micro-segregation of solutes during rapid solidification which create preferential regions for α nucleation. A difference in texture was observed between specimens manufactured with varying laser powers: a low laser power produced a cube texture and a higher laser power produced a // BD fibre texture.

中文翻译：

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激光功率和送粉速度对锻造基体激光金属沉积Ti-5553微观结构演变的影响

摘要 在这项工作中，Ti-5Al-5Mo-5V-3Cr (Ti-5553) 钛块在不同的激光功率和粉末进料速率下激光金属沉积 (LMD) 在相同合金的锻造基体上。微观结构已使用光学显微镜、扫描电子显微镜和电子背散射衍射 (EBSD) 技术进行表征。显微结构主要是与构建方向对齐的大柱状 β 晶粒，散布着细小的等轴 β 晶粒。发现粉末进料速率的增加会降低平均 β 晶粒尺寸并促进细晶粒簇在后续层的沉积过程中得以保留。激光功率的增加还降低了平均 β 晶粒尺寸，并促进了基板界面和初始沉积层处更大的纳米级 α 沉淀物，这显着增加了该区域的显微硬度。由于快速凝固过程中溶质的微偏析而存在枝晶，这为α成核创造了优先区域。在使用不同激光功率制造的样品之间观察到纹理差异：低激光功率产生立方体纹理，而较高激光功率产生 // BD 纤维纹理。