The equilibrium vacancy concentration in an aluminium-copper alloy

Abstract

The equilibrium vacancy concentration in an aluminium-0.41% copper alloy was determined by measuring the difference between the linear expansion and lattice expansion during heating and cooling between 370° and 640°. It was found that the defect concentration in the alloy was the same as that in pure aluminium at all temperatures, from which it is concluded that the free energy of interaction between a vacancy and copper atom in aluminium is zero within the experimental error. Consideration of the possible errors in the measurements indicate that the experimental uncertainty is somewhat greater than 0.1 eV. However, this result provides grounds for rejecting those previous estimates of copper-vacancy binding in excess of 0.15 eV in favour of the more recent work that suggests a very small interaction.