Abstract
In the present work, the solid solubility, formation of compounds and strength in Al alloys have been examined by the calculation of energy and Mulliken’s population of cluster models by the extended Hückel method.
The results of the present work are as follows:
(1) The stability of alloy systems and the nature of chemical bonds between the atoms of Al and the alloying elements can be estimated from the cohesive energy, atomic bond populations and atomic populations.
(2) The tendency of mutual solid solubility, insolubility and compound-formation in Al alloys can be judged as follows:
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oindent(a) In the case of the elements which make compounds and have no mutual solubility with Al, the change of cohesive energy with the composition deviates markedly from lineality and the nature of chemical bonds is ionic or covalent.
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oindent(b) In the case of the elements which make compounds and have mutual solubility with Al, the change of cohesive energy with the composition deviates a little from lineality and the nature of bonds is a mixture of ionic or covalent and metallic bonds.
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oindent(c) In the case of elements which make no compounds and have mutual solubility with Al, the cohesive energy changes linearly with the composition and the nature of bonds is the metallic one or its mixture with covalent or ionic bond.
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oindent(d) In the case of elements which make no compounds and have no mutual solubility with Al, the change of cohesive energy with the composition deviates a little from linearlity and the nature of bonds is anti-bonding.
(3) The hardening ability of solute atoms in Al alloys may be attributed to the (covalent+ionic) part in the nature of chemical bonds between Al atoms and solute atoms.
