P. Charbonnier et al., ATOMIC ORDERING AND MARTENSITIC-TRANSFORMATION IN CU-ZN-AL AND CU-AL-NI INDUSTRIAL ALLOYS, Journal de physique. IV, 5(C2), 1995, pp. 159-163
The isothermal relaxation process near room temperature in b Cu-Zn-Al
and Cu-Zn-Al-Ni industrial alloys which follows a step quenching or an
up quenching thermal treatment has been studied by isothermal calorim
etric technique. The transition temperature Ms and its evolution have
been obtained by differential scanning calorimetry and by detecting th
e acoustic emission. The dissipated energy of the sample measured duri
ng the relaxation process present a complex behaviour, characterized b
y a continuous slowing down. On the other hand, the evolution of MS at
the beginning of the phenomenon obeys a. different law. We show that
all measured evolutions are much more slow in the case of Cu-Zn-Al-Ni
alloy, comparing to Cu-Zn-Al alloy. The presence of nickel, which slow
s diffusion processes can explain this behaviour, influenced by quench
ing rate and annealing time. We interpret the relaxation processes and
the evolutions of Ms in term of atomic reordering (B2 and L21). These
phenomena are so slow in Cu-Zn-Al-Ni alloys near room temperature tha
t the equilibrium state of order cannot be reached.