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Tremsin, A. S.*; Gao, Y.*; Makinde, A.*; Bilheux, H. Z.*; Bilheux, J. C.*; An, K.*; 篠原 武尚; 及川 健一
Additive Manufacturing, 46, p.102130_1 - 102130_20, 2021/10
被引用回数：9 パーセンタイル：57.39(Engineering, Manufacturing)Microstructures produced by Additive Manufacturing (AM) techniques determine many characteristics of components where these materials are used. Residual stress and texture are among those characteristics, which need to be optimized. In this study, we employ energy-resolved neutron imaging to investigate, non-destructively, the uniformity of texture and to map the distribution of strain due to residual stress in Inconel 625 samples. The samples used in this study were printed by a direct metal laser melting additive manufacturing technique. Strain and texture variation are measured at room temperature as well as their changes during annealing at 700
C and 875C in a vacuum furnace. The uniformity of crystalline plane distribution, from which texture can be inferred, is imaged with sub-mm spatial resolution for the entire sample area.
Busi, M.*; Kalentics, N.*; Morgano, M.*; Griffiths, S.*; Tremsin, A. S.*; 篠原 武尚; Log
, R.*; Leinenbach, C.*; Strobl, M.*
Additive Manufacturing, 39, p.101848_1 - 101848_9, 2021/03
被引用回数：14 パーセンタイル：73(Engineering, Manufacturing)Laser powder bed fusion is an efficient technique for additive manufacturing of metallic materials. The quality of the material produced depends on the optimization of a large range of build parameters and the complex thermo- mechanical build process is prone to inducing detrimental material features such as porosity and residual stresses negatively affecting fatigue resistance and lifetime. Here we apply neutron Bragg edge radiography in a para- metric study on printing 316L steel. The parameters concerned are the laser scanning speed and strategy as well as the optional use of support structures. Analyses of the full field single shot wavelength-resolved Bragg edge radiography data enables to characterize local density inhomogeneities, as well as cracks, based on the long wavelength tail of the spectrum and variations of the stress field but also textural features based on the Bragg edge pattern. It is found that in the performed study not only respective differences in the residual stresses due to parameter variation are manifesting but also systematic irregularities due to machine imperfections (e.g. issues with the powder coater) are observed in the printed samples. The study supports the use of the parallel scanning strategy without supports and with the lower utilized scanning speed.
山中 謙太*; 黒田 あす美*; 伊藤 美優*; 森 真奈美*; Bian, H.*; 菖蒲 敬久; 佐藤 茂男*; 千葉 明彦*
Additive Manufacturing, 37, p.101678_1 - 101678_12, 2021/01
被引用回数：24 パーセンタイル：86.75(Engineering, Manufacturing)Ti-6Al-4V alloy is widely used in aerospace and biomedical industries, and its preparation using additive manufacturing techniques has recently attracted considerable attention. Herein, the dislocation structures developed during electron beam and laser beam powder-bed fusion (EB-PBF and LB-PBF, respectively) of the Ti-6Al-4V alloy were quantitatively examined via XRD line profile analysis. Accordingly, a higher dislocation density and finer crystallite size were observed at the top cross-section from the XRD line profile analysis, suggesting that the extent of phase decomposition depended on the duration of the exposure to the elevated temperature. Nonetheless, the saturated dislocation density was as high as 10
m
, where dislocation strengthening affected the overall strength of the EB-PBF specimen. Diffraction peaks of sufficient intensity that enabled the analysis of the dislocation structures in both the 
(')-matrix and the nanosized beta-phase precipitates at the (')-laths were obtained under high-energy synchrotron radiation; this revealed that the beta-phase had a much higher dislocation density than the surrounding (')-matrix. The enhanced dislocation accumulation in the nanosized 
-phase precipitates probably reflects the elemental partitioning that occurred during post-solidification cooling. The valuable insights provided in this study are expected to promote further development of alloy preparation using additive manufacturing processes.
Morgano, M.*; Kalentics, N.*; Carminati, C.*; Capek, J.*; Makowska, M.*; Woracek, R.*; Maimaitiyili, T.*; 篠原 武尚; Loge, R.*; Strobl, M.*
Additive Manufacturing, 34, p.101201_1 - 101201_6, 2020/08
被引用回数：23 パーセンタイル：75.89(Engineering, Manufacturing)Additive manufacturing is a promising and rapidly rising technology in metal processing. However, besides a number of key advantages the constitution of a part through a complex thermo-mechanical process implies also some severe issues with the potential of impacting the quality of products. In laser powder bed fusion (LPBF) the repetitive heating and cooling cycles induce severe strains in the built material, which can have a number of adverse consequences such as deformation, cracking and decreased fatigue life that might lead to severe failure even already during processing. Here we demonstrate how lattice strains implied by LPBF and laser shock peening (LSP) can efficiently be characterized through diffraction contrast neutron imaging. Despite the spatial resolution need with regards to the significant gradients of the stress distribution and the specific microstructure, which prevent the application of more conventional methods, Bragg edge imaging succeeds to provide essential two-dimensionally spatial resolved strain maps in full field single exposure measurements.
