The influence of atmospheres on the mechanical alloying (MA) of Ni-Ti system was investigated using several techniques in this dissertation. It was found that the crystallines directly transformed into amorphous phase by MA in an argon atmosphere; Nitrides or hydride of titanium and/or nickel appeared by MA in nitrogen or hydrogen atmospheres; No intermetallic compounds occurred in above MA processes. When MA was in oxygen atmosphere, it was found that the intermetallic compounds formed besides oxides o titanium and/or nickel. The formation of intermetallic compounds and amorphous phase induced by MA of Ni_xTi_(100-x) (x = 40, 60) in oxygen atmosphere could be attributed to the "self-sustaining" reaction triggered by heat release of oxidation. The "self-sustaining" reaction led to the occurrence of mechanically alloyed in oxygen atmosphere, the existence of oxygen atoms hindered the diffusion of Ti atoms in α-Ni crystal and hence hindered the formation of amorphous phase. When the amorphous powders were mechanically alloyed in oxygen atmosphere, the heat release of oxidation induced the crystallization of amorphous phase and decomposition of intermetallic compounds. The mechanical milling of elemental titanium in Ar atmosphere was also investigated in this dissertation. It was found that the average crystalline size was up to 12-13 nm after 24 hours milling time. The relation of hardness with crystalline size holds for Hall-Petch relation. The detail investigations of solid state reaction between elemental powders (Al, Ni, Fe) and amorphous Fe-Si-B powders were also reported in this dissertation. For the reaction between Al and amorphous Fe_(78)Si_(12)B_(10) powders, it was found that the Al-riched amorphous phase formed. The dissolution of Al into amorphous phase resulted in the formation of stable amorphous phase. Further milling led to the crystallization of the above Al-riched amorphous phase. Increasing the content of Al in the powder mixtures, the powder mixtures transformed into amorphous and/or nanocrystalline phases, The case of solid state reaction between different contents of Ni and amorphous powders Fe_(78)Si_(12)B_(10) was different from that of Al and Fe_(78)Si_(12)B_(10). For the case of low content of Ni, the reaction resulted in the formation of amorphous phase containing Ni. For the case of high content of Ni, the reaction resulted in the formation of amorphous and γ(Fe, Ni) phases. The mechanical milling of Ni and partial amorphous Fe_(78)Si_(12)B_(10) powders resulted in the crystallization of amorphous phase. When Fe and amorphous Fe_(78)Si_(12)B_(10) powders were mechanically alloyed, the dissolution of Fe into amorphous phase resulted in the change of crystallization behaviour and the formation of nanocrystalline Fe. The mechanical milling of crystallized or partially crystallized Fe_(78)Si_(12)B_(10) alloys showed that the nanocrystalline phase was formed after several hours of milling. The comparison of position life times of amorphous, nanocrystalline Fe_(78)Si_(12)B_(10) alloys reflected the differences of defects in different materials.
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