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Hardness and Microstructure of Binary and Ternary Nitinol Compounds

The hardness and microstructure of twenty-six binary and ternary Nitinol compounds (Ni-Ti, Ni-Ti- Ta, Ni-Ti-Hf, and Ni-Ti-Zr) were studied. A small (50g) button of each compound was produced by vacuum arc melting (VAM). Each alloy was homogenized in vacuum for 48 hr followed by furnace cooling. Specimens from the buttons were then heat treated at 800, 900, 1000 or 1100 °C for 2 hr followed by water quenching. The hardness and microstructure of each specimen was compared to the baseline (55-Nitinol, 55 at.% Ni – 45 at.% Ti, after heat treatment at 900 °C). The results show that sixteen of the studied compounds had higher hardness values than the baseline material with relatively low levels of secondary phase precipitation. Moreover, five of these compounds had hardness values greater than or equal to approximately 660HV (≈58HRC) with essentially no property-degrading precipitation phases.

Stanford, Malcolm K.↗

The FOXSI Solar Sounding Rocket Campaigns

The Focusing Optics X-ray Solar Imager (FOXSI) is, in its initial form, a sounding rocket experiment designed to apply the technique of focusing hard X-ray (HXR) optics to the study of fundamental questions about the high-energy Sun. Solar HXRs arise via bremsstrahlung from energetic electrons and hot plasma produced in solar flares and thus are one of the most direct diagnostics of flare-accelerated electrons and the impulsive heating of the solar corona. Previous missions have always been limited in sensitivity and dynamic range by the use of indirect (Fourier) imaging due to the lack of availability of direct focusing optics, but technological advances now make direct focusing accessible in the HXR regime (as evidenced by the NuSTAR spacecraft and several suborbital missions). The FOXSI rocket experiment develops and optimizes HXR focusing telescopes for the unique scientific requirements of the Sun. To date, FOXSI has completed two successful flights on 2012 November 02 and 2014 December 11 and is funded for a third flight. This paper gives a brief overview of the experiment, which is sensitive to solar HXRs in the 4-20 keV range, describes its first two flights, and gives a preview of plans for FOXSI-3.

Glesener, Lindsay↗