Using old and new measurements, the change of the elastic modulus of copper, silver and gold with the addition of B-metals of the Zn and Cd period is analyzed. It is shown that the elastic modulus E in general decreases with alloying. An exception is the addition of Cd and Mg to gold, which increases the elastic modulus. The modulus change ΔE depends on two terms, one being proportional to the concentration c, while the other is proportional to the product of the concentration and the square of the valency difference between the alloying element and the base metal ΔZ. Thus an empirical relationship of the form
ΔE=-βc-αc (ΔZ)2 (1)is obtained. β and α are constants. The value of β only depends on the base metal and the period, being the same for all metals of one period. α increases with the distance of the period from the base metal in the periodic table. Experiments on poly-and single crystals give the same results.
ΔC'R=(Kβ2-β1)c+Kα2cΔZ-α1c(ΔZ)2 (2)where K, β2 and α2 are constants.
(1/a)(da/dc)=β2+α2ΔZ. (3)Because β2 may be positive or negative depending on the system studied, the lattice parameter may increase or decrease with alloying. Therefore, the change of the lattice parameter cannot be used for a unique explanation of the change of the elastic modulus due to alloying.
* Commemorative Lecture, Annual Meeting of the Japan Institute of Matals, Tokyo, 4∼6 April, 1971.
** Prof. Dr. phil. Dr. -Ing. E. h., Max-Planck-Institut für Metallforschung, Stuttgart, West Germany.
© 2002 The Japan Institute of Metals
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