作者weakhsuan (科科)
看板NTUMSE-98
标题[物冶] 第五次小考详解
时间Fri Oct 29 09:53:48 2010
Physical Metallurgy Test 5 (October 28, 2010)
系级__________ 学号__________ 姓名__________
1.In early material studies, a discrepancy of many orders of magnitude existed
between the theoretical and observed yield stresses of crystals. Which model
can explain the observed low values of strength? How to explain. (10%)
dislocation
A few atoms move from low energy position on dislocation, no need of
all atoms on slip planes.
2.In an actual crystal, because of the more complex spatial arrangement of
atoms, the dislocations are complicated and often difficult to visualize.
However, two terms can be used to completely describe the dislocations.
Point out these two terms. (10%)
Burgers vector, dislocation line
3.The figure in Fig. 1 shows the orientation of a discolation line along the
direction of positive line sense. Is i a right-hand or left-hand screw
dislocation? Determine its Burgers vector according to the orientation of
the dislocation line. (20%)
left-hand, Burgers vector 略
4.The photograph in Fig. 2 shows a growth spiral on the surface of a crystal;
the crystal grows as a never-ending spiral. Can you indicate which type of
dislocation is associated with this typical spiral pattern? (20%)
screw dislocation
5.It has been well known that in FCC metal crystal, (111) planes are the
closest-packed planes and with the stacking sequence of ABCABC... If the
_
movement of an atom on B plane by a shear 1/2[110] relative to the
neighboring C plane, can this atom remain in the B stacking. Why?
Give your reason. (20%)
_
Yes, (1) 1×1－1×1＋0×1＝0 → 1/2[110] is on (111)
_
(2) 1/2[110] 也是FCC的最密方向, 滑移後仍然是B stacking.
shortest, lattice translation(左边这个字我不确定= =) vector
6.Fig.3 plots the stereographic projection of a cubic crystal for the planes
of a zone with the zone axis [100]. Fig. 4 shows the electron diffraction
pattern corresponding to the electron beam directed along [100] in a cubic
crystal. By useing these two figures, make a brief comment on the
relationship between the reciprocal lattice and the electron diffraction
pattern. (20%)
l(011)/l(010)=d(010)/d(011)=(a/1)/(a/√2)=√2
(1) reciprocal lattice 的比例会和结晶面的间距成倒数关系
(2) electron diffraction pattern 的方向会和 standard projection的方向一样
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这次详解教授没有提供
是助教影印Taddy的考卷然後他自己再加一些补充上去的
以上答案不代表本人立场
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1F：推 cj1234:推 10/29 19:57
2F：推 taddy441:为什麽是印我的??我都不知道 10/29 22:14
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※ 编辑: weakhsuan 来自: 111.240.34.9 (10/29 22:22)
4F：→ weakhsuan:已修正 10/29 22:22