Browsing by Subject "Micro-structural properties"

Now showing 1 - 2 of 2

Open Access
Formation of B19′, B2, and amorphous phases during mechano-synthesis of nanocrystalline NiTi intermetallics
(Elsevier BV, 2014-02) Amini, R.; Alijani, F.; Ghaffari, M.; Alizadeh, M.; Okyay, Ali Kemal
Ni-50Ti shape memory alloy was synthesized by mechanical alloying of the elemental powders mixture under an argon gas atmosphere. The structural and microstructural properties of the alloyed powders were evaluated by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Moreover, the Vickers microhardness of the powders was estimated at different milling times. According to the results, by milling progression, the amount of the amorphous phase increased considerably and after sufficient milling time (48h), the mechano-crystallization of the amorphous phase into the more stable crystalline phases (i.e. B2 and B19') occurred. It was found that the particles size and microhardness were significantly affected by the formation of the amorphous, B2, and B19' phases. It was also deduced that, by appropriate heating and cooling cycles, the B2 and thermally-induced B19' phases can be created. Furthermore, it was inferred that the formation of undesirable intermetallic phases (particularly NiTi2) during the heating cycle was considerably reduced by milling time evolution. © 2013 Elsevier B.V.
Open Access
Properties of high specific strength Al-4wt.% Al2O3/B4C nano-composite produced by accumulative roll bonding process
(Elsevier Ltd, 2013) Alizadeh, M.; beni H.A.; Ghaffari, M.; Amini, R.
The influence of nano-scale reinforcement on the mechanical and microstructural properties of ultrafine-grained composites was studied. Al matrix (pure aluminum) composites, with a grain size of 230nm and B4C and Al2O3 reinforcements with an average size of 50nm, were fabricated via the accumulative roll bonding (ARB) process. To evaluate structure and microstructure of the produced composites, X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) were applied. Mechanical properties of the specimens were investigated by tensile and hardness tests. The result revealed that in comparison with monolithic Al (ARBed Al without ceramic particles), the presence of nano-particles enhances specific strength of composites. Also, the results showed that with increasing ARB cycles, the microhardness of the composites increases. In addition, the specific strength and microhardness of the composite samples are higher than those of the monolithic Al. The density of the composite samples and monolithic Al was measured by the Archimedes method showing that the density decreases in presence of ceramic particles. © 2013 Elsevier Ltd.