Examination of carbon partitioning into austenite during tempering of bainite

The redistribution of carbon after tempering of a novel nanocrystalline bainitic steel consisting of a mixture of supersaturated ferrite and retained austenite has been analyzed by atom probe tomography. No direct evidence supporting the additional carbon enrichment of austenite beyond that initially achieved during the bainite heat treatment was obtained during subsequent tempering of this high carbon, high silicon steel.The authors gratefully acknowledge the support of the Research Fund for Coal and Steel and the Spanish Ministry of Science and Innovation for funding this research under the contracts RFSR-CT-2008-00022 and MAT2007 – 63873, respectively. Research at the Oak Ridge National Laboratory SHaRE User Facility was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. A.J. Clarke gratefully acknowledges support from Los Alamos National Security, LLC, operator of the Los Alamos National Laboratory under contract number DE-AC52-06NA25396 with the U.S. Department of Energy and the Advanced Steel Processing and Products Research Center, a National Science Foundation Industry/University Cooperative Research Center at the Colorado School of Mines and the Inter-American Materials Collaboration ProgramPeer reviewe

Atmospheric corrosion of copper in Ibero-America

Within the framework of the American Map of Atmospheric Corrosiveness (MICAT) project, 4 years of field research on atmospheric corrosion carried out in 14 countries of Ibero-America, this paper reports atmospheric copper corrosion in 21 unpolluted rural atmospheres and 45 marine atmospheres covering a broad interval of climatic conditions. High temperatures and relative humidities seem to promote greater copper corrosion in rural atmospheres: Attack rates are found in the range of 0.1 μm/y to 2 μm/y, and corrosion product layers, generally comprising only cuprite (Cu2O), are discontinuous and have open structures with patinas acquiring increasingly darker colors (from salmon pink to dull brown) with exposure time. From the results obtained at marine sites, a critical deposition rate threshold is inferred for atmospheric salinity (20 mgCl-/m2 per day), after which the atmospheric corrosion of this material is intensified.Peer Reviewe

Comparison of performance of self-expanding and balloon-expandable transcatheter aortic valves

Objective: To evaluate the flow dynamics of self-expanding and balloon-expandable transcatheter aortic valves pertaining to turbulence and pressure recovery. Transcatheter aortic valves are characterized by different designs that have different valve performance and outcomes. Methods: Assessment of transcatheter aortic valves was performed using self-expanding devices (26-mm Evolut [Medtronic], 23-mm Allegra [New Valve Technologies], and small Acurate neo [Boston Scientific]) and a balloon-expandable device (23-mm Sapien 3 [Edwards Lifesciences]). Particle image velocimetry assessed the flow downstream. A Millar catheter was used for pressure recovery calculation. Velocity, Reynolds shear stresses, viscous shear stress, and pressure gradients were calculated. Results: The maximal velocity at peak systole obtained with the Evolut R, Sapien 3, Acurate neo, and Allegra was 2.12 ± 0.19 m/sec, 2.41 ± 0.06 m/sec, 2.99 ± 0.10 m/sec, and 2.45 ± 0.08 m/sec, respectively (P \u3c .001). Leaflet oscillations with the flow were clear with the Evolut R and Acurate neo. The Allegra shows the minimal range of Reynolds shear stress magnitudes (up to 320 Pa), and Sapien 3 the maximal (up to 650 Pa). The Evolut had the smallest viscous shear stress magnitude range (up to 3.5 Pa), and the Sapien 3 the largest (up to 6.2 Pa). The largest pressure drop at the vena contracta occurred with the Acurate neo transcatheter aortic valve with a pressure gradient of 13.96 ± 1.35 mm Hg. In the recovery zone, the smallest pressure gradient was obtained with the Allegra (3.32 ± 0.94 mm Hg). Conclusions: Flow dynamics downstream of different transcatheter aortic valves vary significantly depending on the valve type, despite not having a general trend depending on whether or not valves are self-expanding or balloon-expandable. Deployment design did not have an influence on flow dynamics