Samples prepared are shown in Table 2. The results obtained are as follows:
(1) Room temperature age-hardening. Some researcher did not observe the room temperature age-hardening, but we observed it in “A 10” and “A 20” alloys. (Fig. 1 & 2).
(2) Form of age-hardening curves and its activation energy. We studied age-hardening of “A 20” alloy at 30°, 50°, 70° and 90°, and obtained next results. Denoting hardening degree by
p and ageing time by
t,
p⁄1−
p is proportinal to
tn, and at 50°, 70° and 90°,
n=1. From these results actvation energy at these stages was calculated and obtained
Q=8,200 cal/mol. (Fig. 3-5).
(3) Double aging. We expected double age-hardening of these alloys as well as Al-Cu alloys, so studied it in “B 20” alloy. As expected,we could observe double aging clearly between 140° and 200°. (Fig. 6-8).
(4) Relation between aging temperature
T in absolute scale and the time at which the alloy at a given temperature
T reaches maximum hardness. This relation was studied from the data of “B 20” alloys between 140° and 350°, and we obtained the result that log
t depends linearly on 1⁄
T and activation energy
Q at these stages is 22,000 cal/mol. (Fig. 9).
(5) Dehardening (“Rückbildung”) phenomena. We studied dehardening phenomena in “A 10” and “A 20” alloys which were aged at 30° for long time or at 150° for 5 hours. And we observed distinctly dehardening phenomena when alloys treated for very short time at the optimum temperature. (Fig. 11-20).
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