VALENCE ELECTRON STRUCTURE ANALYSIS OF EQUILIBRIUM AND METASTABLE PHASES OF Al3M(M=Ti, Zr, Hf)
HUANG Lian, GAO Kunyuan, WEN Shengping, HUANG Hui, WANG Wei, NIE Zuoren
College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124
Cite this article:
HUANG Lian, GAO Kunyuan, WEN Shengping, HUANG Hui, WANG Wei, NIE Zuoren. VALENCE ELECTRON STRUCTURE ANALYSIS OF EQUILIBRIUM AND METASTABLE PHASES OF Al3M(M=Ti, Zr, Hf). Acta Metall Sin, 2012, 48(4): 492-501.
Abstract The valence electron structure of Al3M(M=Ti, Zr, Hf) with three crystal structures (L12, D022, D023) and the corresponding strongest bond energy (EA) values have been calculated from the empirical electron theory (EET) of solids and molecules. Based on the calculated EA, the stability of the phases with different structures and the sequence of phase transition have been analyzed semi--quantitatively. The results showed that, the EA of the equilibrium phases, i.e., D022-Al3Ti, D023-Al3Zr and D022-Al3Hf, were 57.7, 71.6 and 75.6 kJ/mol, respectively, which showed the same trend in magnitude with the corresponding melting point. This consistence supports the reliability of EET--based calculation results. Similarly, the EAof Al3Ti, Al3Zr and Al3Hf with three structures have been calculated and the calculated phase transition sequences are the same as the experimental results and those from first--principles calculation. The L12-type metastable phases of three intermetallic compounds exhibit many excellent characteristics, whereas their phase stability is crucial for application. The EA is supposed to be a measure for the stability of metastable phase. The calculated EA of L12 structure implied the phase stability in the order of Al3Ti3Zr3Hf, which was the same as that from the transition temperatures experimentally. The EA calculated by EET, therefore, could be a good measure for the stability of metastable phase.
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