The Science and Technology of 3D Printing

Three-dimensional printing, or additive manufacturing, is an emerging manufacturing process. Research and development are being performed worldwide to provide a better understanding of the science and technology of 3D printing to make high-quality parts in a cost-effective and time-efficient manner. This book includes contemporary, unique, and impactful research on 3D printing from leading organizations worldwide

Investigation of Microstructure and Mechanical Properties for Ti-6Al-4V Alloy Parts Produced Using Non-Spherical Precursor Powder by Laser Powder Bed Fusion

An unmodified, non-spherical, hydride-dehydride (HDH) Ti-6Al-4V powder having a substantial economic advantage over spherical, atomized Ti-6Al-4V alloy powder was used to fabricate a range of test components and aerospace-related products utilizing laser beam powder-bed fusion processing. The as-built products, utilizing optimized processing parameters, had a Rockwell-C scale (HRC) hardness of 44.6. Following heat treatments which included annealing at 704 °C, HIP at ~926 °C (average), and HIP + anneal, the HRC hardnesses were observed to be 43.9, 40.7, and 40.4, respectively. The corresponding tensile yield stress, UTS, and elongation for these heat treatments averaged 1.19 GPa, 1.22 GPa, 8.7%; 1.03 GPa, 1.08 GPa, 16.7%; 1.04 GPa, 1.09 GPa, 16.1%, respectively. The HIP yield strength and elongation of 1.03 GPa and 16.7% are comparable to the best commercial, wrought Ti-6Al-4V products. The corresponding HIP component microstructures consisted of elongated small grains (~125 microns diameter) containing fine, alpha/beta lamellae

Investigation and Mitigation of Powder Anomalies Induced Porosity in Powder Bed Additive Manufacturing

Defect content is one of the major obstacles to the wider adoption of additive manufacturing (AM) as the field is still actively learning how to control it, developing standards to quantify it, and building up knowledge of its formation and impacts. On the other hand, there is a growing interest in reducing AM fabrication cost by using recycled materials and economically produced powder. State-of-the-art powder-based AM processes typically accept gas-atomized spherical powder with low entrapped gas porosity. However, using non-standard powder feedstock, e.g., the non-spherical hydride-dehydride (HDH) Ti-6Al-4V powder and the highly porous 17-4 PH stainless steel powder, can be more cost-efficient. This work presents two successful applications of the non-standard feedstocks through process optimization by measuring the process windows for the fully dense components and achieving comparable mechanical properties as the standard AM counterparts. Additionally, the author used synchrotron based high-speed imaging technique to visualize and quantify the porosity formation processes induced by the anomalies of the non-standard powders, i.e., irregular morphology and powder porosity. By coupling them with pore shape analysis and powder packing analysis, three powder induced porosity formation mechanisms were proposed. Melt pool dynamics, powder packing characteristics, and powder-laser interactions are believed to be the key factors for powder induced porosity formation. The optimization guideline and the better understanding of the porosity formation can certainly be generalized for the application of other non-standard feedstocks which could benefit the AM community.</p