Article
Chemistry, Physical
Yujian Wang, Junjie Li, Jianwei Li, Lei Zhang, Jiankai Ma, Zhijun Wang, Feng He, Jincheng Wang
Summary: Coarsening of the basketweave alpha + beta microstructure in Ti-6Al-4V during thermal cycling is driven by multiple dissolution and precipitation transformations instead of conventional Ostwald ripening. This study reveals that the vanishing of alpha plates continues during repeated thermal cycling through two mechanisms, which are related to the Gibbs-Thomson effect. The influence of cycling frequency and total duration on the coarsening transformation is also detected. Long cycling duration leads to severe coarsening, while the final coarsening of alpha plates is almost independent of the cycling frequency.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Chemistry, Physical
Haoyang Li, Taomei Zhang, Dan Li, Yiyou Wu, Zhaowen Geng, Chao Chen, Xiaoyong Zhang, Kechao Zhou
Summary: In this study, a eutectoid Ti-7Ni alloy was additively manufactured using E-PBF. The effects of electron beam current and preheating time on the microstructure and mechanical properties of the alloy were investigated. It was found that the microstructure of the alloy can be controlled through in-situ heat treatment, leading to good mechanical properties.
Article
Electrochemistry
Patrick T. Brewick
Summary: This study investigates the impact of crystallographic features of additive manufactured (AM) microstructures on the pitting corrosion process through computational simulations. The results demonstrate that the AM-informed models produce larger, deeper pits with multiple locations of elevated stress concentrations along the pit front.
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
(2022)
Article
Chemistry, Physical
O. B. Perevalova, M. S. Syrtanov
Summary: The microstructure and phase composition of the EBAM Ti-6Al-4 V alloy samples during heating were studied using in situ high temperature synchrotron X-ray diffraction and transmission electron microscopy (TEM). The formation of a new α'' phase and the lattice distortion of the α phase were observed, and the dependence of phase composition on heating temperature was revealed.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Engineering, Manufacturing
Min Yang, Lu Wang, Wentao Yan
Summary: Metal matrix composite parts fabricated by additive manufacturing are of interest due to their fine grain structures and superior mechanical properties. A phase-field model was developed to simulate the grain evolution of TiB2/316L stainless steel composite during the selective laser melting process. The simulation results demonstrate that TiB2 particles influence grain evolutions, leading to the formation of both columnar and equiaxed grains. Increasing TiB2 content decreases grain size and brings equiaxed grains closer to the fusion boundary of the scanning track.
ADDITIVE MANUFACTURING
(2021)
Article
Chemistry, Physical
Mina Zhang, Xianglin Zhou, Dafeng Wang, Longjun He, Xuyang Ye, Wenwu Zhang
Summary: The application scope and market demand for additive-manufactured high-entropy alloys (AM HEAs) have broadened of late. A dual-phase AlCoCuFeNi HEA was fabricated by selective electron beam melting (SEBM) with superior compressive strength and ductility. Further improvements were achieved using selective electron beam remelting (SEB-RM) during SEBM, resulting in better compressive properties.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Engineering, Manufacturing
Jinghao Li, Xianglin Zhou, Qingbo Meng, Mathieu Brochu, Nejib Chekir, J. J. Sixsmith, J. Y. Hascoet, Yaoyao Fiona Zhao
Summary: In this study, a new solidification microstructure model called the invasion model is proposed for metal additive manufacturing (MAM) applications. By focusing on the interaction between neighboring bi-crystals and understanding the grain boundary tilt as transient invasion behavior, the model aims to improve simulation accuracy. Additionally, an artificial neural network (ANN) was utilized to establish a database for anisotropic growth effects, and the model was validated using Ti6Al4V thin-wall samples fabricated by wire feed directed energy deposition (DED).
ADDITIVE MANUFACTURING
(2021)
Article
Nanoscience & Nanotechnology
Sneha Goel, Enrico Zaninelli, Tejas Gundgire, Magnus Ahlfors, Olanrewaju Ojo, Uta Klement, Shrikant Joshi
Summary: Electron beam melting produced Alloy 718 underwent thermal post-treatment including hot isostatic pressing (HIPing) and heat treatment (HT). The study showed significant densification with HIPing at 1120 degrees C, potential for shorter HT duration, and successful integration of HIPing with HT. Tensile response was mainly affected by aging treatment, and shortening HIPing duration and possibly eliminating solution treatment step could improve fatigue life when prior HIPing is performed.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Materials Science, Multidisciplinary
Mohammad Saleh Kenevisi, Cristian Ghibaudo, Emilio Bassini, Daniele Ugues, Giulio Marchese, Sara Biamino
Summary: Electron beam melting (EBM) is a promising technique for processing gamma-TiAl alloys that are prone to cracking. TiAl alloys are usually built on stainless steel platforms to reduce costs, but the interface between the samples and the platform is brittle due to element diffusion, making them easily separable. In this study, Ti-48Al-2Cr-2Nb samples were processed via EBM and separated from the platform without altering the interface layer. The results showed the formation of hard intermetallics and phases close to the interface, and only Fe significantly diffused past the interface.
Article
Nanoscience & Nanotechnology
Hideaki Nishikawa, Yoshiyuki Furuya, Houichi Kitano, Terumi Nakamura, Kosuke Kuwabara, Yoshiharu Kanegae, Dong-Soo Kang, Kinya Aota
Summary: In this study, the microscopic fatigue crack initiation and growth behavior of rolled plate and additively-manufactured nickel base 718 alloy were observed. It was found that the specimens with a robust (001) texture, prepared using EBM and EBAM methods, had shorter fatigue lives compared to the rolled plate and SLM specimens. The early stage cracks were found to initiate and grow along the {111} slip plane, and in the EBAM specimens, the cracks propagated straight to an adjacent grain due to their (001) texture.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2022)
Article
Engineering, Manufacturing
Narendran Raghavan, Benjamin C. Stump, Patxi Fernandez-Zelaia, Michael M. Kirka, Srdjan Simunovic
Summary: This study investigates the correlation between spot-melt scan parameters, build geometry, and solidification microstructure evolution in a powder bed fusion technology. It is found that adjusting the areal energy density per layer with respect to the 2D cross-sectional area is necessary to maintain equiaxed solidification microstructure in electron beam powder bed additive manufacturing. Increasing areal energy density transitioned the solidification microstructure from columnar to equiaxed, and the observed microstructure data was quantified using a spatial statistics methodology. Additionally, a semi-analytical model was used to simulate heat transfer and solidification conditions, which was correlated with previously quantified microstructure data.
ADDITIVE MANUFACTURING
(2021)
Article
Engineering, Manufacturing
Ken Cho, Hajime Kawabata, Tatsuhiro Hayashi, Hiroyuki Y. Yasuda, Hirotoyo Nakashima, Masao Takeyama, Takayoshi Nakano
Summary: The microstructure and tensile properties of beta-containing Ti-44Al-4Cr alloy rods produced by electron beam melting (EBM) were investigated, showing the formation of two different microstructures depending on the input energy density. The strength of the alloys was found to be closely related to the volume fractions of the beta phase and the ultrafine alpha(2)/gamma lamellar grains formed under low energy density conditions. The alloys with these unique microstructures exhibited high strength compared to conventional beta-containing gamma-TiAl at room temperature and 1023 K.
ADDITIVE MANUFACTURING
(2021)
Article
Materials Science, Multidisciplinary
Masaya Higashi, Kyosuke Yoshimi
Summary: This study systematically investigated the effect of preheating on cracking behavior and microstructure evolution of brittle Mo-Si-B based alloys using EBM. The results showed that multi-track scanning with preheating could completely suppress crack formation, expanding the potential of EBM for manufacturing high-temperature and high-strength materials.
MATERIALS & DESIGN
(2021)
Article
Nanoscience & Nanotechnology
Hao Deng, Sheng Cao, James C. Williams, Longqing Chen, Wenbin Qiu, Lvjun Zhou, Jun Tang
Summary: This study investigated the microstructure evolution and mechanical properties of a near beta alloy Ti-5Al-5Mo-5V-3Cr-1Zr fabricated by additive manufacturing. It found that a graded hierarchical microstructure was formed in-situ from an alpha+beta lamellar microstructure at the specimen bottom to an alpha p+alpha s bi-lamellar microstructure at the specimen top, which resulted in a hardening effect attributed to the precipitation of fine secondary alpha.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Materials Science, Multidisciplinary
Xuewei Tao, Ke Han, Shaolong Zhang, Yihao Zhu, Baosen Zhang, Zhengjun Yao, Haixia Liu
Summary: Wire-feed electron beam additive manufacturing was used to repair the damaged Ti6Al4V alloy. The study investigated the effect of heat input on the repaired microstructure and properties of the alloy. The results showed that the sizes of prior columnar grains and laths increased with increased heat input. The increased heat input reduced the microhardness and wear resistance of the repaired zone, but it still remained superior to the mechanical properties of the substrate.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
