高校问答歌曲梅花引简谱:300分工科材料类英文论文求好翻译.4
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For the discontinuous coarsening of DP in AIZn
and AlZn-2Cu alloys at the temperatures of 200 and
250℃, the growth velocity of coarsening cells was
determined. The nucleation of discontinuous coars-
ening was at the primitive boundaries and the DP
cellular boundaries. Therefore, the maximum length
from the original boundaries or cellular boundaries
of DP to the growth front of DC cells, and the trans-
formation time of DC (the aging time subtracted by
the time needed for DP) was measured. So the ratio
of the former to the latter was the growth velocity of
DC, as shown in figure 3. When DP in the AlZn and
AlZn-2Cu alloys began to coarsen discontinuously,
the growth velocity of DC cells rapidly reached the
maximum and then decreased monotonously with
the increase of aging time. Moreover, the growth
velocity of DC cells at 250℃ was quicker than that
at 200℃; the growth velocity of DC cells in the ter-
nary alloy was slower than that in the binary alloy.
At the beginning of DC, the growth velocity of
DC cells rapidly reached the maximum due to the
maximum driving force. With the extension of aging
time,the driving force of DC was reduced, and at
the same time, the amount of DC nucleus increased.
Thereby, the further growth of DC was restrained,
and the growth velocity was reduced. With the ele-
vation of aging temperature, the atomic diffusion
was accelerated, which led to the increase in growth
velocity.
The DC volume fractions of DP in the AIZn and
AlZn-2Cu alloys aged at temperatures of 200 and
2500C were determined by the secant method of op-
tical microscope (figure 4). It can be seen that the
transformation speed of DC at 2000C was quicker
than that at 2500C, which was opposite to the result
of the growth velocity of DC cell. It was implied that
the transformation speed of DC was related not only
to the growth velocity of DC cells, but also to the
amount of DC nucleation. At the aging temperature of 200℃, the size of DP cells was small, and the
area of cellular boundaries was large. Therefore, the
regions suitable for the nucleation of DC increased,
and the amount of nucleus increased. Although the
growth velocity was slow, the volume of DC in-
creased.
The experimental result was fitted by the follow-
ing equation of Johnson-Mehl-Avrami (JMA) to ob-
tain the Avrami index n:
f=1一exp(-kt") (1)
where f represents the volume fraction of DC, and t
represents the transformation time of DC.
3.2 动能学不连续coarsening 为不连续coarsening DP 在AIZn 和AlZn-2Cu 合金里在温度200 和250?, 成长速度coarsening 细胞是坚定的。不连续的coars- 的生核ening 是在原始界限和DP 多孔的界限。所以, 最大长度从原始的界限或DP 多孔的界限对DC 细胞成长前线, 和DC 的trans- 形成时期(老化时间减去了当需要为DP) 的时候被测量了。如此比前与后者是成长速度DC, 依照被显示在上图3 。当DP 在AlZn 和AlZn-2Cu 合金开始不连续地coarsen, 成长速度DC 细胞迅速地到达了最大值和单调然后减少了以老化时间增量。而且, 成长速度DC 细胞在250? 比那快的在200?; 成长速度DC 细胞在ter- 毫无合金比那慢的在二进制合金。在DC 开始, 成长速度DC 细胞迅速地到达了最大值由于最大驱动力。以老化时间引伸, DC 驱动力被减少了, 和同时, 相当数量DC 中坚力量被增加。从而, DC 进一步成长被克制了, 并且成长速度被减少了。与老化温度的ele- vation, 原子扩散加速了, 导致在成长速度的增量。DP 的DC 容量分数在AIZn 和AlZn-2Cu 合金变老在温度200 和2500C 由正割方法操作tical 显微镜确定了(图4) 。它能被看见, DC 的变革速度在2000C 比那快的在2500C, 是相对于成长速度的结果DC 细胞。它被暗示, DC 的变革速度不仅与成长速度DC 细胞有关, 而且对相当数量DC 生核。在老化温度200?, DP 细胞的大小小, 并且多孔的界限区域是大的。所以, 地区适当为DC 的生核被增加, 和相当数量中坚力量增加了。虽然成长速度是慢的, DC 的容量在弄皱。实验性结果由约翰逊的跟随ing 等式Mehl Avrami 适合了(JMA) 对ob- tain Avrami 索引n: f=1?exp(千吨") (1) f 代表DC 的容量分数的地方, 和t 代表DC 的变革时期。