Browsing by Subject "Micro-structural characterization"

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    Investigation of grain refinement in Al/Al2O3/B 4C nano-composite produced by ARB
    (2014) Akbari Beni H.; Alizadeh, M.; Ghaffari, M.; Amini, R.
    In this study, Al/Al2O3/B4C nano-composites were fabricated via the accumulative roll bonding (ARB) process. The grain refinement of the Al/Al2O3/B4C nano-composite strips during the ARB process was studied. Microstructural characterizations of the fabricated composites after 2, 5, and 9 cycles were performed by transmission electron microscopy (TEM). The results showed that the composite sample, after 9 cycles, was filled with homogenously distributed ultra fine grains with an average grain size of 230 nm. The findings also revealed that the increase in the dislocation density due to the presence of the nano-sized particles resulted in the grain refinement of the specimens. It was also found that the grain refinement is accelerated by the presence of the refinement particles. © 2013 Elsevier Inc. All rights reserved.
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    Microstructural characterization of medical-grade stainless steel powders prepared by mechanical alloying and subsequent annealing
    (Elsevier, 2013) Salahinejad, E.; Hadianfard, M. J.; Ghaffari, M.; Amini, R.; Mashhadi, S. B.; Okyay, Ali Kemal
    The harmful effect of nickel ions released from conventional stainless steel implants has provided a high level of motivation for the further development of nickel-free stainless steels. In this paper, the microstructure of medical-grade nickel-free stainless steel powders, with the chemical composition of ASTM F2581, is studied during mechanical alloying and subsequent annealing. Rietveld X-ray diffraction and transmission electron microscopy evaluations reflect nanocrystallization, austenitization and amorphization of the powders due to mechanical activation. It is also realized that annealing of the as-milled powder can develop a single austenitic structure with nanometric crystallite sizes, implying a considerable inherent resistance to grain growth. This study demonstrates the merit of mechanical alloying and subsequent annealing in the development of nanostructured medical-grade stainless steels.