Het nitreren van Fe-Cr legeringen

Technische MateriaalwetenschappenApplied Science

Precipitate Formation in Low-Temperature Nitrided Cold-Rolled Fe94Ni4Ti2 and Fe93Ni4Cr3 Films

Using various experimental techniques, the formation and evolution of precipitates, the dilation of the matrix, and the nitrogen uptake and release were investigated in cold-rolled Fe94Ni4Ti2 and Fe93Ni4Cr3 materials subjected to nitriding in a gaseous mixture of NH3 + H2 and to reduction in an H2 atmosphere at low (300 °C) to moderate (600 °C) temperatures. Transmission electron microscopy (TEM) revealed that in both alloys the precipitates are thin platelets. In the Ti-containing alloy, the precipitates were also small in the lateral dimensions. The difference in size, aspect ratio of the precipitates, and misfit and coherency on the interface consistently explain the substantial differences in dilation of the matrix and nitrogen uptake for the Ti- and Cr-containing alloys under examination. The results provide evidence for the formation of mixed Fe-Ti-N precipitates (Guinier–Preston (GP) zones) in the early stages of nitriding.

The eleventh and twelfth data releases of the Sloan Digital Sky Survey : final data from SDSS-III

The third generation of the Sloan Digital Sky Survey (SDSS-III) took data from 2008 to 2014 using the original SDSS wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new nearinfrared high-resolution spectrograph, and a novel optical interferometer. All of the data from SDSS-III are now made public. In particular, this paper describes Data Release 11 (DR11) including all data acquired through 2013 July, and Data Release 12 (DR12) adding data acquired through 2014 July (including all data included in previous data releases), marking the end of SDSS-III observing. Relative to our previous public release (DR10), DR12 adds one million new spectra of galaxies and quasars from the Baryon Oscillation Spectroscopic Survey (BOSS) over an additional 3000 deg2 of sky, more than triples the number of H-band spectra of stars as part of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and includes repeated accurate radial velocity measurements of 5500 stars from the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The APOGEE outputs now include the measured abundances of 15 different elements for each star. In total, SDSS-III added 5200 deg2 of ugriz imaging; 155,520 spectra of 138,099 stars as part of the Sloan Exploration of Galactic Understanding and Evolution 2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies, 294,512 quasars, and 247,216 stars over 9376 deg2; 618,080 APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5513 stars. Since its first light in 1998, SDSS has imaged over 1/3 of the Celestial sphere in five bands and obtained over five million astronomical spectra