50 research outputs found
Microstructure, Oxidation Behavior And Mechanical Behavior Of Lens Deposited Nb-Ti-Si And Nb-Ti-Si Based Alloys
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Additive Manufacturing of Inconel 718 using Electron Beam Melting: Processing, Post-Processing, & Mechanical Properties
No full textAdditive Manufacturing (AM) process parameters were studied for production of the high temperature alloy Inconel 718 using Electron Beam Melting (EBM) to better understand the relationship between processing, microstructure, and mechanical properties. Processing parameters were analyzed for impact on process time, process temperature, and the amount of applied energy. The applied electron beam energy was shown to be integral to the formation of swelling defects. Standard features in the microstructure were identified, including previously unidentified solidification features such as shrinkage porosity and non-equilibrium phases. The as-solidified structure does not persist in the bulk of EBM parts due to a high process hold temperature (~1000��C), which causes in situ homogenization. The most significant variability in as-fabricated microstructure is the formation of intragranular delta-phase needles, which can form in samples produced with lower process temperatures (< 960��C). A novel approach was developed and demonstrated for controlling the temperature of cool down, thus providing a technique for in situ heat treatment of material. This technique was used to produce material with hardness of 478��7 HV with no post-processing, which exceeds the hardness of peak-aged Inconel 718. Traditional post-processing methods of hot isostatic pressing (HIP) and solution treatment and aging (STA) were found to result in variability in grain growth and phase solution. Recrystallization and grain structure are identified as possible mechanisms to promote grain growth. These results led to the conclusion that the first step in thermal post-processing of EBM Inconel 718 should be an optimized solution treatment to reset phase variation in the as-fabricated microstructure without incurring significant grain growth. Such an optimized solution treatment was developed (1120��C, 2hr) for application prior to aging or HIP. The majority of as-fabricated tensile properties met ASTM AM Inconel 718 standards for yield stress and ultimate tensile strength, and STA yield stress, ultimate tensile strength, and elongation exceeded the ASTM standards for AM Inconel 718
Human protein C concentrate in the treatment of purpura fulminans : a retrospective analysis of safety and outcome in 94 pediatric patients
No full textIntroduction: Purpura fulminans (PF) is a devastating complication of uncontrolled systemic inflammation, associated with high incidence of amputations, skin grafts and death. In this study, we aimed to clarify the clinical profile of pediatric patients with PF who improved with protein C (PC) treatment, explore treatment effects and safety, and to refine the prognostic significance of protein C plasma levels. Methods: In Germany, patients receiving protein C concentrate (Ceprotin(R), Baxter AG, Vienna, Austria) are registered. The database was used to locate all pediatric patients with PF treated with PC from 2002 to 2005 for this National, retrospective, multi-centered study. Results: Complete datasets were acquired in 94 patients, treated in 46 centers with human, non-activated protein C concentrate for purpura fulminans. PC was given for 2 days (median, range 1-24 days) with a median daily dose of 100 IU/kg. Plasma protein C levels increased from a median of 27% to a median of 71% under treatment. 22.3% of patients died, 77.7% survived to discharge. Skin grafts were required in 9.6%, amputations in 5.3%. PF recovered or improved in 79.8%, remained unchanged in 13.8% and deteriorated in 6.4%. Four adverse events occurred in 3 patients, none classified as severe. Non-survivors had lower protein C plasma levels (P < 0.05) and higher prevalence of coagulopathy at admission (P < 0.01). Time between admission and start of PC substitution was longer in patients who died compared to survivors (P = 0.03). Conclusions: This retrospective dataset shows that, compared to historic controls, only few pediatric patients with PF under PC substitution needed dermatoplasty and/or amputations. Apart from epistaxis, no bleeding was observed. Although the data comes from a retrospective study, the evidence we present suggests that PC had a beneficial impact on the need for dermatoplasty and amputations, pointing to the potential value of carrying out a prospective randomised controlled trial
Data for Investigating the Effect of Metal Powder Recycling in Electron Beam Powder Bed Fusion using Process Log Data
No full textThis archive contains log file data that was generated by the Arcam A2 Electron Beam Melting (EBM) (R) system during the build process of different builds. The purpose of the builds was to study the effect of recycling of metal powder on the chemical composition, flowability and size characteristics of powder. A detailed exposition of findings from the study is available in reference [1]. The powders studied were Inconel 718 and Ti-6Al-4V alloy powders. The original log file data generated by Arcam EBM has been pruned to include only parameters described in the Column header description section of this file
Fatigue crack growth mechanisms at the microstructure scale in as-fabricated and heat treated Ti-6Al-4V ELI manufactured by electron beam melting (EBM)
No full textPublisher Copyright: © 2017Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that fabricates parts by selectively scanning consecutive powder layers with an electron beam. Additive manufacturing technologies are increasing in importance for aerospace and medical applications, where the demand for a fundamental understanding and predictability of static and dynamic material properties are high. Ti-6Al-4V is the most widely used and studied alloy for this technology, and is the focus of this work in its Extra Low Interstitial (ELI) variation. The layered manufacturing of metallic components by EBM creates a unique directional microstructure, and consequently, anisotropic properties. Microstructure evolution, and its influence on mechanical properties of the alloy in the as-fabricated condition, has been documented by various researchers. However, fatigue crack propagation and the effects of the directional structure have not been sufficiently studied, imposing a barrier for this technology's potential extension to high-integrity applications. In this study, fatigue crack growth (FCG) both parallel and perpendicular to the build directions was studied for different stress ratios and crack growth stages. The interaction between the directional as-fabricated EBM microstructure and FCG was investigated and compared to that of the equiaxed β annealed microstructure obtained by annealing above the β transus temperature. The FCG threshold, ΔKth, was analytically modeled for the two relative crack propagation directions at different stress ratios, and FCG microstructural mechanisms were established for all three regions of crack propagation.This research was performed under the Additive Manufacturing program of the Integrative Material Design Center (iMdc) at Worcester Polytechnic Institute, in collaboration with the Additive Manufacturing Demonstration Facility of Oak Ridge National Laboratory, and sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. Ph.D. candidates Yuwei Zhai and Anthony Spangenberger of the iMdc also collaborated actively in the material characterization performed during this study.Peer reviewe
Thermographic in-situ process monitoring of the electron-beam melting technology used in additive manufacturing
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