H. Tsubakino et al., PRECIPITATION SEQUENCE FOR SIMULTANEOUS CONTINUOUS AND DISCONTINUOUS MODES IN CU-BE BINARY-ALLOYS, Materials science and technology, 9(4), 1993, pp. 288-294
The precipitation sequence of the discontinuous and continuous modes i
n Cu-0-9Be and Cu-1.4Be binary alloys (compositions in wt-%) has been
studied primarily via metallographic observations and hardness measure
ments. A single C curve and triple C curves separated by two temperatu
res T1 and T2 (T1 > T2) are obtained for the precipitation of disconti
nuous and continuous modes, respectively. The triple C curves correspo
nd to the formation of gamma, gamma', and Guinier-Preston (GP) zones.
The precipitation sequence of these two precipitation modes and the ce
ll growth behaviour are different for the following three temperature
ranges defined by the triple C curves: (i) above T1, discontinuous pre
cipitation occurs before the continuous precipitation of gamma phase,
and the cell growth rate G decreases abruptly; (ii) between T1 and T2,
the precipitation sequence is similar to that above T1, but G decreas
es and interlamellar spacing increases progressively with aging time;
(iii) below T2, GP zones, fine gamma'', and/or fine gamma' form before
cell growth but the associated variation in G is not observed. The ef
fect of continuous precipitation on the cell growth behaviour is discu
ssed.