On amorphization and nanocomposite formation in Al-Ni-Ti system by mechanical alloying |
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Authors: | N. Das G. K. Dey B. S. Murty S. K. Pabi |
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Affiliation: | (1) Metallurgical and Materials Engineering Department, Indian Institute of Technology, 721 302 Kharagpur, India;(2) Bhabha Atomic Research Centre, 400 085 Mumbai, India;(3) Metallurgical and Materials Engineering Department, Indian Institute of Technology-Madras, 600 036 Chennai, India |
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Abstract: | Amorphous structure generated by mechanical alloying (MA) is often used as a precursor for generating nanocomposites through controlled devitrification. The amorphous forming composition range of ternary Al-Ni-Ti system was calculated using the extended Miedema’s semi-empirical model. Eleven compositions of this system showing a wide range of negative enthalpy of mixing (−ΔH mix) and amorphization (−ΔH amor) of the constituent elements were selected for synthesis by MA. The Al88Ni6Ti6 alloy with relatively small negative ΔH mix (−0.4 kJ/mol) and ΔHamor (−14.8 kJ/mol) became completely amorphous after 120 h of milling, which is possibly the first report of complete amorphization of an Al-based rare earth element free Al-TM-TM system (TM = transition metal) by MA. The alloys of other compositions selected had much more negative ΔHmix and Hamor; but they yielded either nanocomposites of partial amorphous and crystalline structure or no amorphous phase at all in the as-milled condition, evidencing a high degree of stability of the intermetallic phases under the MA environment. Hence, the negative ΔH mix and ΔH amor are not so reliable for predicting the amorphization in the present system by MA |
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Keywords: | Nanocomposite amorphization mechanical alloying Miedema model Al-Ni-Ti system |
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