The ultrasonic attenuation A and the elastic constants C-44, C-1 and C' hav
e been measured during thermal cycles carried out above the martensite star
t-temperature M-s (M-s = 267 K) in a single crystal of the Cu67.93Zn19.03Al
13.04 alloy. The ultrasonic attenuation displays a sharp maximum at a tempe
rature which is about 6 degrees higher than M-s. This temperature differenc
e can be accounted for either in terms of the Clausius-Clapeyron law for th
e martensite induced by the applied ultrasonic stress-held or in terms of p
remartensitic effects. Thermal hysteresis occurs for all the elastic consta
nts C-44, C-1 and C' and the data are consistent with those previously obta
ined for the Young's modulus in a polycrystalline alloy of the same system.
The thermal hysteresis is attributed to the formation of stable nuclei of
martensite at strong defects. (C) 2000 Elsevier Science S.A. All rights res
erved.