Search

C250 maraging steel, known for its high strength and good toughness, is ideal for applications requiring exceptional high strain rate properties. Its carbon-free composition is suitable for the directed energy deposition-arc (DED-Arc) method, an additive manufacturing (AM) process with a low cost and high deposition rate. However, the thermal cycles in DED-Arc significantly impact the microstructure of C250 alloy. This could lead to undesirable high strain rate properties, necessitating post-fabrication heat treatment. Research gaps remain in understanding the microstructure and dynamic deformation response of DED-Arc fabricated C250 steel. Besides, AM enables fabricating complex geometries, but accurate constitutive models governing the stress-strain relationship of materials are essential for reliable finite element analysis (FEA) predictions of dynamic deformation. Yet, no reliable models have been proposed to predict the dynamic deformation behaviors of DED-Arc built C250 alloy. Therefore, this study aims to investigate the microstructure and dynamic deformation responses of DED-Arc built C250 steel at different strain rates and temperatures and to develop appropriate constitutive models based on the observed flow behavior. Microstructure analyses indicate the absence of strengthening precipitates and the presence of retained austenite phase in as-built DED-Arc C250 steel, leading to inferior dynamic mechanical performance compared to heat-treated wrought C250 alloy. However, commercial heat treatment significantly improves the dynamic mechanical performance of heat-treated DED-Arc C250 steel, making it comparable to that of the heat-treated wrought C250 alloy. This substantial improvement is mainly attributed to the formation of nano-sized, needle-shaped, and coherent Ni3Mo strengthening precipitates during the heat treatment. Modifications are made to the Johnson-Cook constitutive models to predict the dynamic deformation behaviors of as-deposited and heat-tre

Dental implants are vital in modern dentistry, offering a durable and effective solution for various dental issues. Since their introduction for edentulous jaws, implants have been recognized as a reliable option for replacing missing teeth. Recent advancements in digital engineering, such as cone beam computed tomography (CBCT) and computer-aided design (CAD) techniques, have further enhanced implant dentistry. High-quality CT scans and sophisticated segmentation software now facilitate the reverse engineering of implants, enabling the creation of patient-specific root analog implants. This process involves generating computer models that accurately replicate anatomical features, including teeth. Direct metal laser sintering (DMLS), an additive manufacturing method, can then produce these customized implants, offering a faster and more patient-friendly alternative to traditional methods. The project's goal is to advance implant dentistry by developing a semi-automated protocol for patient-specific implants. This protocol aims to promote the adoption of root analog implants produced via DMLS. The developed tools will help dental professionals manage complex cases more effectively, benefiting many patients and improving implant survival rates. This approach also simplifies the implantation process, reducing the technological burden on dental professionals. Initially focused on custom-made implants, the project revealed inconsistencies in current fabrication methods, highlighting the need for standardized procedures. Our key achievements include a comprehensive review of custom-made root analog implants (RAIs). We developed a modeling protocol to convert CBCT scans of roots into scaffold roots, tested it with plastic prototypes, and manufactured titanium RAIs, which were CT-scanned and mechanically tested. Our findings indicate that the field of custom-made implant fabrication is still developing, with no standardized methods or clear guidelines. The modeling protocol

Considerable focus has been directed toward investigating the interdiffusion coefficients in binary systems, primarily due to their pivotal role in metallurgical processes and material performance assessments. An essential parameter in this context is the isothermal concentration-dependent interdiffusion coefficient. While interdiffusion coefficients are widely recognized as being influenced by temperature and concentration, the element of time can exert substantial influence due to the presence of diffusion-induced stress (DIS) within the system. The present research experimentally investigates the effect of time on concentration-dependent interdiffusion and impurity diffusion coefficients in Cu-Ni binary systems and their alloy compositions. The investigation delves into the effect of solute source concentration and anomalous behaviors of temperature as the attributable indications of DIS at play. To implement the research work, a newly devised numerical diffusion model by Olaye and Ojo [20] is integrated with a forward simulation approach in this study. This model incorporates different atomic diffusion coefficients and ensures solute conservation. The model also merges fully explicit finite difference analyses with the Leapfrog/Dufort-Frankel scheme, thus enabling the determination of concentration-dependent interdiffusion coefficients. This approach overcomes the limitations associated with traditional techniques like the Boltzmann-Matano, Hall, Wagner and Sauer-Freise methods. By applying this method, both the interdiffusion and impurity diffusion coefficients are investigated at various diffusion times. The results reveal that the interdiffusion and impurity diffusion coefficients show time variations as a result of DIS in the system. This phenomenon contrasts the widely accepted notion of the interdiffusion coefficient being solely dependent on concentration and temperature without considering time. Overlooking this critical aspect could have substantial imp

The influence of pulsed laser beam welding (LBW) parameters on theweld geometry and imperfections of a new nickel-based superalloy called G27 wasstudied by a statistical design of experiment, and the microstructures of the weldfusion zone (FZ) of the pulsed laser beam-welded G27 were characterized. Noevidence of cracks is found in the FZ and heat-affected zone (HAZ). Other weldimperfections, such as undercut and underfill, were also hardly observed. The pulsefactor significantly influenced all the responses, i.e., minimum weld width (Wm),root excess weld metal, and average pore diameter, whereas welding travel speedsignificantly influenced Wm and root excess weld metal. Power and interactionbetween pulse frequency*pulse factor were statistically significant in influencingthe root excess weld metal and average pore diameter, respectively. The pulsefrequency and interactions between power*travel speed, power*pulse factor,power*pulse frequency, travel speed*pulse factor, and travel speed*pulse frequencydid not significantly influence any response. Microsegregation pattern that occursduring weld solidification leads to the formation of Nb-rich MC carbides and Nbrich Laves phase as the major secondary phase constituents in the FZ of as-weldedG27. The presence of brittle Laves phase requires careful consideration whendeveloping suitable post-weld heat treatment of G27., CC-BY-NC 4.0This study is based on the research conducted within the FEAST project (WeldFeasibility Heat Treatment Studies of New Superalloys, registration number 2019-02787) funded by the Swedish funding agency VINNOVA