Transparent spinel ceramics were additively manufactured by laser direct deposition, a blown powder additive manufacturing (AM) process. With a laser melt-growth process, the need for powder binders and postprocessing procedures was eliminated. Transparent spinel ceramic samples were directly fabricated from micrometer-size magnesium aluminate spinel powders. The optical transparency of the printed spinel samples was mainly affected by residual porosity and cracking. Among other processing conditions, powder flow rate and laser power showed the most significant effects. An obvious transition from opaqueness to transparency was observed after reducing the powder flow rate below 0.1 g/min. The optical transmittance, morphology, and phase composition of the printed spinel samples were systematically investigated. Microstructural aspects including porosity, cracking, and grain size were also characterized. A maximum optical transmittance of 82% was obtained at a wavelength of 632.8 nm, which was nearly comparable to that of their traditionally sintered counterparts. As the laser power increased, residual porosity steadily decreased, with a minimum porosity of 0.2% achieved. Meanwhile, the total crack length obviously increased, while a relatively smaller variation of the average crack length was observed. The measured mechanical properties, including hardness and fracture toughness, were found to be nearly comparable to those of their sintered counterparts. These well demonstrated the potential of the proposed laser AM method in the direct fabrication of transparent ceramics.

中文翻译：

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透明铝酸镁尖晶石陶瓷的直接3D打印

透明尖晶石陶瓷通过激光直接沉积，吹塑粉末增材制造（AM）工艺进行增材制造。通过激光熔体生长工艺，消除了对粉末粘合剂和后处理程序的需求。透明尖晶石陶瓷样品直接由微米尺寸的铝酸镁尖晶石粉末制成。印刷的尖晶石样品的光学透明性主要受残余孔隙率和开裂的影响。在其他加工条件中，粉末流速和激光功率显示出最显着的效果。将粉末流速降低至0.1 g / min以下后，观察到了从不透明性到透明性的明显转变。系统地研究了印刷的尖晶石样品的透光率，形态和相组成。微观结构方面，包括孔隙率，开裂和晶粒尺寸也得到了表征。在632.8 nm的波长处获得82％的最大透光率，这几乎与传统烧结的同类产品相当。随着激光功率的增加，残余孔隙率稳步下降，最小孔隙率达到0.2％。同时，总裂纹长度明显增加，而平均裂纹长度的变化相对较小。发现所测量的机械性能，包括硬度和断裂韧性，几乎与它们的烧结对等物相当。这些很好地证明了所提出的激光AM方法在直接制造透明陶瓷中的潜力。在632.8 nm的波长处获得82％的最大透光率，这几乎与传统烧结的同类产品相当。随着激光功率的增加，残余孔隙率稳步下降，最小孔隙率达到0.2％。同时，总裂纹长度明显增加，而平均裂纹长度的变化相对较小。发现所测量的机械性能，包括硬度和断裂韧性，几乎与它们的烧结对等物相当。这些很好地证明了所提出的激光AM方法在直接制造透明陶瓷中的潜力。在632.8 nm的波长处获得82％的最大透光率，这几乎与传统烧结的同类产品相当。随着激光功率的增加，残余孔隙率稳步下降，最小孔隙率达到0.2％。同时，总裂纹长度明显增加，而平均裂纹长度的变化相对较小。发现所测量的机械性能，包括硬度和断裂韧性，几乎与它们的烧结对等物相当。这些很好地证明了所提出的激光AM方法在直接制造透明陶瓷中的潜力。残余孔隙率稳步下降，最小孔隙率达到0.2％。同时，总裂纹长度明显增加，而平均裂纹长度的变化相对较小。发现所测量的机械性能，包括硬度和断裂韧性，几乎与它们的烧结对等物相当。这些很好地证明了所提出的激光AM方法在直接制造透明陶瓷中的潜力。残余孔隙率稳步下降，最小孔隙率达到0.2％。同时，总裂纹长度明显增加，而平均裂纹长度的变化相对较小。发现所测量的机械性能，包括硬度和断裂韧性，几乎与它们的烧结对等物相当。这些很好地证明了所提出的激光AM方法在直接制造透明陶瓷中的潜力。