Grain size stability in a cryomilled nanocrystalline Al alloy powders containing diamantane nanoparticles

Abstract

The thermal stability of nanocrystalline Al-5083 alloy powders stabilized by diamantane molecular diamonds was compared with that of the nanocrystalline Al-5083 alloy powders with no diamantane. Both materials were produced by mechanical milling in a liquid nitrogen medium. The results revealed that Al-5083 with diamantane exhibited greater thermal stability than the alloy without diamantane in the temperature range of 473 °K to 773 °K (0.56 to 0.91Tm) for various annealing times from 0.5 h to 48 h. In this regard, calculations showed that while the grain size was still in the nanoscale range (< 100 nm) in the presence of diamantane, it was in the ultrafine range (> 150 nm) in the absence of diamantane. The above finding can be qualitatively explained in terms of Zener's particle pinning concept. The stability of nanocrystalline Al-5083 powder by adding diamantane is discussed in terms of retaining the nanostructure and maintaining hardness and strength over long periods of time when the powder is used in surface coating via cold spray