@article{NadammalCabezaMishurovaetal.2017, author = {Nadammal, Naresh and Cabeza, Sandra and Mishurova, Tatiana and Thiede, Tobias and Kromm, Arne and Seyfert, Christoph and Farahbod, Lena and Haberland, Christoph and Schneider, Judith Ann and Portella, Pedro Dolabella and Bruno, Giovanni}, title = {Effect of hatch length on the development of microstructure, texture and residual stresses in selective laser melted superalloy Inconel 718}, series = {Materials \& Design}, volume = {134}, journal = {Materials \& Design}, publisher = {Elsevier}, address = {Oxford}, issn = {0264-1275}, doi = {10.1016/j.matdes.2017.08.049}, pages = {139 -- 150}, year = {2017}, abstract = {In the present study, samples fabricated by varying the deposition hatch length during selective laser melting of nickel based superalloy Inconel 718 were investigated. Microstructure and texture of these samples was characterized using scanning electron microscopy, combined with electron back-scattered diffraction, and residual stress assessment, using neutron diffraction method. Textured columnar grains oriented along the sample building direction were observed in the shorter hatch length processed sample. A ten-fold increase in the hatch length reduced the texture intensity by a factor of two attributed to the formation of finer grains in the longer hatch length sample. Larger gradients of transverse residual stress in the longer hatch length sample were also observed. Along the build direction, compressive stresses in the shorter hatch length and negligible stresses for the longer hatch length specimen were observed. Changes to the temperature gradient (G) in response to the hatch length variation, influenced the G to growth rate (R) ratio and the product GxR, in agreement with the microstructures and textures formed. For the residual stress development, geometry of the part also played an important role. In summary, tailored isotropy could be induced in Inconel 718 by a careful selection of parameters during selective laser melting.}, language = {en} } @article{MishurovaCabezaThiedeetal.2018, author = {Mishurova, Tatiana and Cabeza, Sandra and Thiede, Tobias and Nadammal, Naresh and Kromm, Arne and Klaus, Manuela and Genzel, Christoph and Haberland, Christoph and Bruno, Giovanni}, title = {The Influence of the Support Structure on Residual Stress and Distortion in SLM Inconel 718 Parts}, series = {Metallurgical and Materials Transactions A}, volume = {49A}, journal = {Metallurgical and Materials Transactions A}, number = {7}, publisher = {Springer}, address = {New York}, issn = {1073-5623}, doi = {10.1007/s11661-018-4653-9}, pages = {3038 -- 3046}, year = {2018}, abstract = {The effect of support structure and of removal from the base plate on the residual stress state in selective laser melted IN718 parts was studied by means of synchrotron X-ray diffraction. The residual stresses in subsurface region of two elongated prisms in as-built condition and after removal from the base plate were determined. One sample was directly built on a base plate and another one on a support structure. Also, the distortion on the top surface due to stress release was measured by contact profilometry. High tensile residual stress values were found, with pronounced stress gradient along the hatching direction. In the sample on support, stress redistribution took place after removal from the base plate, as opposed to simple stress relaxation for the sample without support. The sample on support structure showed larger distortion compared to sample without support. We conclude that the use of a support decreases stress values but stress-relieving heat treatments are still needed.}, language = {en} } @article{ThiedeCabezaMishurovaetal.2018, author = {Thiede, Tobias and Cabeza, Sandra and Mishurova, Tatiana and Nadammal, Naresh and Kromm, Arne and Bode, Johannes and Haberland, Christoph and Bruno, Giovanni}, title = {Residual Stress in Selective Laser Melted Inconel 718}, series = {Materials performance and characterization}, volume = {7}, journal = {Materials performance and characterization}, number = {4}, publisher = {American Society for Testing and Materials}, address = {West Conshohocken}, issn = {2379-1365}, doi = {10.1520/MPC20170119}, pages = {717 -- 735}, year = {2018}, abstract = {The residual stress distribution in IN718 elongated prisms produced by selective laser melting was studied by means of neutron (bulk) and laboratory X-ray (surface) diffraction. Two deposition hatch lengths were considered. A horizontal plane near the top surface (perpendicular to the building direction) and a vertical plane near the lateral surface (parallel to the building direction) were investigated. Samples both in as-built (AB) condition and removed from the base plate (RE) were characterized. While surface stress fields seem constant for the AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e., with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the base plate.}, language = {en} } @article{NadammalMishurovaFritschetal.2021, author = {Nadammal, Naresh and Mishurova, Tatiana and Fritsch, Tobias and Serrano-Munoz, Itziar and Kromm, Arne and Haberland, Christoph and Portella, Pedro Dolabella and Bruno, Giovanni}, title = {Critical role of scan strategies on the development of microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing}, series = {Additive manufacturing}, volume = {38}, journal = {Additive manufacturing}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2214-8604}, doi = {10.1016/j.addma.2020.101792}, pages = {13}, year = {2021}, abstract = {Laser based powder bed fusion additive manufacturing offers the flexibility to incorporate standard and user-defined scan strategies in a layer or in between the layers for the customized fabrication of metallic components. In the present study, four different scan strategies and their impact on the development of microstructure, texture, and residual stresses in laser powder bed fusion additive manufacturing of a nickel-based superalloy Inconel 718 was investigated. Light microscopy, scanning electron microscopy combined with electron back-scatter diffraction, and neutron diffraction were used as the characterization tools. Strong textures with epitaxially grown columnar grains were observed along the build direction for the two individual scan strategies. Patterns depicting the respective scan strategies were visible in the build plane, which dictated the microstructure development in the other planes. An alternating strategy combining the individual strategies in the successive layers and a 67 degrees rotational strategy weakened the texture by forming finer micro-structural features. Von Mises equivalent stress plots revealed lower stress values and gradients, which translates as lower distortions for the alternating and rotational strategies. Overall results confirmed the scope for manipulating the microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing by effectively controlling the scan strategies.}, language = {en} } @article{WeberAbuAyyashAbueladasetal.2009, author = {Weber, Michael H. and Abu-Ayyash, Khalil and Abueladas, Abdel-Rahman and Agnon, Amotz and Alasonati-Taš{\´a}rov{\´a}, Zuzana and Al-Zubi, Hashim and Babeyko, Andrey and Bartov, Yuval and Bauer, Klaus and Becken, Michael and Bedrosian, Paul A. and Ben-Avraham, Zvi and Bock, G{\"u}nter and Bohnhoff, Marco and Bribach, Jens and Dulski, Peter and Ebbing, Joerg and El-Kelani, Radwan J. and Foerster, Andrea and F{\"o}rster, Hans-J{\"u}rgen and Frieslander, Uri and Garfunkel, Zvi and G{\"o}tze, Hans-J{\"u}rgen and Haak, Volker and Haberland, Christian and Hassouneh, Mohammed and Helwig, Stefan L. and Hofstetter, Alfons and Hoffmann-Rothe, Arne and Jaeckel, Karl-Heinz and Janssen, Christoph and Jaser, Darweesh and Kesten, Dagmar and Khatib, Mohammed Ghiath and Kind, Rainer and Koch, Olaf and Koulakov, Ivan and Laske, Maria Gabi and Maercklin, Nils}, title = {Anatomy of the Dead Sea transform from lithospheric to microscopic scale}, issn = {8755-1209}, doi = {10.1029/2008rg000264}, year = {2009}, abstract = {Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (similar to 20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the mu m to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.}, language = {en} } @article{OnckenLuschenMechieetal.1999, author = {Oncken, Onno and Luschen, Ewald and Mechie, James and Sobolev, Stephan Vladimir and Schulze, Albrecht and Gaedicke, Christoph and Grunewald, Steffen and Bribach, Jens and Asch, G{\"u}nter and Giese, Peter and Wigger, Peter and Schmitz, Michael and Lueth, Stefan and Scheuber, Ekkehard and Haberland, Christian and Rietbrock, Andreas and G{\"o}tze, Hans-J{\"u}rgen and Brasse, Heinrich and Patzwahl, Regina and Chong, Guillermo and Wilke, Hans-Gerhard and Gonzalez, Gabriel and Jensen, Arturo and Araneda, Manuel and Vieytes, Hugo and Behn, Gerardo and Martinez, Eloy}, title = {Seismic reflection image revealing offset of Andean subduction-zone earthquake locations into oceanic mantle}, year = {1999}, language = {en} }