Powder Materials Processing and Fundamental Understanding: Characterization and Analysis II
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee
Program Organizers: Elisa Torresani, San Diego State University; Kathy Lu, University of Alabama Birmingham; Eugene Olevsky, San Diego State University; Ma Qian, Royal Melbourne Institute of Technology; Diletta Giuntini, Eindhoven University of Technology; Paul Prichard, Kennametal Inc.; Wenwu Xu, San Diego State University

Thursday 2:00 PM
March 23, 2023
Room: 25B
Location: SDCC

Session Chair: Nicholas Derimow, National Institute of Standards and Technology; Wenwu Xu, San Diego State University


2:00 PM  Invited
X-ray Synchrotron Imaging of Laser Melted Ti-6Al-4V Powders with Varying Oxygen Content, Powder Size Distributions, and Gaseous Environments: Nicholas Derimow1; Orion Kafka1; Samuel Clark2; Jake Benzing1; Ed Garboczi1; Nik Hrabe1; 1National Institute of Standards and Technology; 2Argonne National Laboratory
    Titanium alloy (Ti-6Al-4V) is widely used in the biomedical and aerospace industries for its high strength-to-weight ratio and good corrosion resistance. However, as laser powder-bed fusion (PBF-L) additive manufacturing (AM) advances towards reliable production of titanium parts, it has yet to be fully realized for fracture critical applications due to an incomplete understanding of the processing-structure-properties-performance relationships (PSPP). To understand the PSPP relationships in titanium PBF-L, a study of the laser melting was paired with high-speed X-ray synchrotron imaging (beamline: 32-ID APS). Simultaneous melting and imaging was carried out on both grades of Ti-6Al-4V (Grades 5 and 23) at different power levels, powder size distributions, and gaseous environments (Ar and He) atop AM Ti-6Al-4V baseplates. Geometrical representations of the differing melt pool dynamics will be discussed. Ex situ, postmortem microstructural analysis of the fusion and heat affected zones between the melted powder and base metal will also be presented.

2:30 PM  
The Improvement of Surface Roughness on Vertical Surfaces for 316L Stainless Steel in Laser Powder Bed Fusion Additive Manufacturing: Tianyu Zhang1; Lang Yuan1; 1University of Southern California
    In the laser powder bed fusion process, the surface roughness plays an important role in the geometrical accuracy and mechanical properties. Understanding and improving the surface roughness is required to improve the quality of products. In the prior study, the roughness of vertical surfaces is dominated by the dross formation under high laser energy density conditions and by partially melted particle and melt pool tracks under low energy density conditions. In this study, Alternating contour parameters, implementing contour remelting, and utilizing pulse laser are executed to improve the vertical surface roughness by eliminating the factors listed above. The surface roughness is measured by Keyence optical microscopy and the melt pool morphology and microstructure are gathered from the cross-section view via SEM. The effectiveness and underlying mechanisms of the different methods are analyzed and discussed based on the experiment results. Better surface quality has been achieved under different energy density levels.

2:50 PM  Cancelled
Unveiling New Insights into Computer Vision and Machine Learning for Reusability Assessment of Ti-6Al-4V Powder in Additive Manufacturing: Saeid Alipour Masoumabad1; Sanaz Vajedian1; Arezoo Emdadi1; 1Missouri University of Science & Technology
    This research aims to introduce a novel approach to evaluate the reusability of Ti-6Al-4V powders for powder bed fusion additive manufacturing using computer vision and machine learning. Virgin powders were compared to powders that had been used in the process up to 16 times. The Python-based implemented approach outcome is to estimate the powder flowability, which has been used up to 16 times in the process, based on the powder SEM images. To this end, 11 different geometrical defects in powders including agglomerates, broken particle, bonded particles, internal porosity, clip-cap, and their effects on the powder flowability are considered. The accuracy of the proposed approach compared with the existing approaches. The results achieved here can contribute to the development of guidelines on metallic powder reuse based on morphological features and applying computer vision and machine learning in powder bed fusion additive manufacturing.

3:10 PM  
Metal Powder Characterization Through the Experimental Method and Machine Learning Approach in Selective Laser Melting: Jiahui Zhang1; Manvinder Lalh1; Yu Zou1; 1University of Toronto
    In the selective laser melting process, the metal powder properties, e.g., powder packing behavior and flowability, have been reported to significantly affect the formation of anomalies inside the as-fabricated parts. In our recent studies, We investigate the effect of particle size distribution on powder flowability and apply a computer vision approach to evaluate powder flowability. Our results indicate: (1) Either a larger mean particle size or a narrower particle size distribution enhances the powder flowability; The multimodal distribution of PSD is beneficial for the powder bulk flow properties. (2) Feature-based image representation models are established to evaluate powder flowability based on scanning electron microscopy images. Our works provide an effective and efficient tool to evaluate and predict the powder flowability for AM.

3:30 PM Break

3:50 PM  
Mapping Directed Energy Deposition of Nickel Superalloys Through In-situ Synchrotron Radiography: Imogen Cowley1; Yunhui Chen2; Sebastian Marussi1; Kai Zhang1; Chu Lun Alex Leung1; Marta Majkut3; Maureen Fitzpatrick1; Martyn Jones4; Peter Lee1; 1University College London; 2University of Manchester; 3European Synchrotron Radiation Facility; 4Rolls-Royce plc.
    Directed Energy Deposition (DED) is an Additive Manufacturing (AM) technology which offers new repair capabilities for high-value superalloy aerospace components. However, DED-produced components are susceptible to heterogeneity and defects (such as porosity, cracking, lack-of-fusion, and poor surface finish). Current research relies upon post-build ex situ analysis of samples to relate process parameters to resulting microstructural features and material properties, and there is a lack of understanding of the dynamic physical mechanisms that underpin these relationships. Here, in situ and operando synchrotron radiography (ESRF ID-19, beamtime MA4857) is used to study Blown-Powder DED of RR1000, a nickel superalloy used in turbine disk applications, to map process-microstructure-property relationships and reveal underlying physical phenomena. Process phenomena and microstructural features are analysed for a range of processing parameters, and new dynamic defect formation phenomena were observed, from which quality-optimisation strategies are proposed.

4:10 PM  
Methodology for Material Selection of Optimal Additive Manufactured Alloys and Parameter Sets for Space Optical Instruments: Zachary Post1; Walter Zimbeck1; Steven Storck1; Floris van Kempen2; Gerard Otter2; John Boldt1; Ludger van der Laan2; Steven Szczesniak1; Ryan Carter1; Robert Mueller1; Salahudin Nimer1; Doug Trigg1; Michael Berkson1; Frank Morgan1; William Swartz1; 1JHU APL; 2TNO
    A methodology for selecting an optimal additive manufactured (AM) alloy and associated laser parameter set was developed to identify a specific aluminum alloy for laser powder bed fusion (L-PBF) production of parts of the Compact Hyperspectral Air Pollution Sensor (CHAPS). Alloys with higher strength than standard L-PBF AlSi10Mg alloy (7A77, A20X, Scalmalloy, and 6061-RAM2C) were identified and compared over several rounds of testing to find the optimal combination of material and parameters. Round 1 verified sufficient density and tensile properties could be achieved. Round 2 confirmed which laser parameters produced representative CHAPS geometries with high print quality. Round 3 measured build orientation anisotropy and compatibility of material with mirror processing steps. Utilizing weighted criteria specific to CHAPS, test results were binned into categories and the final quality score was calculated. Scalmalloy produced the best quality score and was used to produce a tensile B-basis, topology optimized housings and lightweighted mirrors.

4:30 PM  
Thermogravimetric Analysis of Additive Ti-6Al-4V Powders in Gaseous Environments: Nicholas Derimow1; Elisabeth Mansfield1; Nik Hrabe1; 1National Institute of Standards and Technology
    In titanium alloy (Ti-6Al-4V) powder-bed fusion (PBF), powder feedstock is reused to maintain optimal process cost, with oxygen increases being the limiting factor to reuse. Typically, powder is blended and reused until oxygen content reaches unacceptable levels. This oxidation occurs thermodynamically due to titanium’s gettering properties occurring more rapidly at elevated temperatures. Throughout the PBF and reuse process, these powders can be exposed to a variety of thermal histories and cover gas environments. This work assesses the oxidation kinetics of Ti-6Al-4V alloy of varying grade (Grade 5 and Grade 23) and powder size distributions. The effects of different cover gasses (Ar, He) and in situ gas purification will be discussed.

4:50 PM  
The Microstructure and Hardness of Zn-3(wt.%)Mg Powders Processed via High Pressure Torsion: Tanzilur Rahman1; Burak Dikici2; Hakan Yılmazer3; Kaveh Edalati4; Hendra Hermawan5; Carl Boehlert1; 1Michigan State University; 2Ataturk University; 3Yildiz Technical University; 4Kyushu University; 5Laval University
    Pure zinc (Zn) and magnesium (Mg) powders, in a mass ratio of Zn-3Mg, were high-pressure torsion (HPT) processed using a pressure of 6.0 GPa for 1, 5, 10, 20, and 30 revolutions at room temperature. In order to understand the effects of preconsolidation on the resulting microstructure and hardness, HPT processing was performed on lose powders placed in the die (case 1) and also on a compact (case 2), where the powders were first pressed together prior to HPT processing. The processed samples were characterized by X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, and Vickers microhardness. In both cases, the resulting microstructures contained nanoscale grains and the resulting Hv values were greater than those of both pure Zn and pure Mg. For case 1, the hardness values did not change as a function of the sample radius. The results were compared to HPT processed Zn-Mg alloys and hybrids.

5:10 PM  
Novel Method of BiFeO3 Purification by Acid Washing Determined from ICP-MS Analyses: Jenna Metera1; Anna Wilke1; Olivia Graeve1; 1University of California San Diego
    Ceramic powders produced by hydrothermal synthesis are generally pure in terms of the target composition. However, BiFeO3 produced by this method is not always pure, resulting in the presence of unwanted phases such as Bi2Fe4O9 and Bi25FeO39. Acid washing of powders generally allows for preferential dissolution of unwanted phases in the powder materials over several minutes. However, this approach has not been successfully performed with BiFeO3, therefore the main goal of this work was to evaluate different acids (HBr, HCl, H2SO4, H3PO4, H3BO3, CH3COOH, and HNO3) for this purpose. HBr was concluded to be the optimum acid, since it not only successfully preserves the surface of BiFeO3 powders, but also preferentially dissolves Bi25FeO39 unwanted phase in under 10 minutes (the Bi2Fe4O9 phase was not dissolved by any acid). This work moves the electroceramics industry closer to a scalable material synthesis technique for BiFeO3.