An investigation of elastic moduli of alpha copper-aluminium alloys

The results of ultrasonic measurements of wave velocities in polycrystalline samples of pure copper and four copper-aluminium alloys, containing up to 16.6 at.% Al, show that the three elastic moduli, K, G and E, decrease with increasing aluminium content. The relative effect of the alloying, calculated for pure copper from the average slope of values of the measured moduli between 4.2 and 16.6 at.% Al, is 0.338 for K, 0.384 for G and 0.379 for E. In all three cases the contribution to the total change from the increase in interatomic distances is negative, while that from the increase in the electron concentration is positive. The measured values of the moduli agree fairly well with the values corresponding to recent precision measurements on single crystals.