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小王子柏然

铜虫 (初入文坛)

应助: 0 (幼儿园)
金币: 230
帖子: 9
在线: 7小时
虫号: 2785816
注册: 2013-11-07
专业: 生物医用高分子材料

[求助] 求助关于位错密度等问题，如图所示

A tilt boundary along the xy-plane can be envisaged to consist of a series of parallel edge
dislocations, all with the same Burgers vector b with a length of 0.23 nm. The boundary has
dimensions of x = 30 μm by y = 15 μm. The tilt angle ・is 6o around an axis in the x direction.
A) What is the direction of the dislocation lines (x, y or z)?

B) What is the distance between dislocations in the boundary, both in meters and in number
of atomic distances?
C) Calculate the dislocation density ρ・(defined as dislocation line length per unit of volume)
in a volume x × y × z = 30 μm × 15 μm × 1 μm enclosing the grain boundary.
D) In the case of a random distribution of dislocations the dislocation energy per unit of
volume is given by Ed = ½μb2ρ, with μ the shear modulus (160 GPa). Discuss the relation
between this dislocation energy and the interfacial energy γ.
E) Calculate Ed from the dislocation density found in question c)
F) Give the equation expressing the relation between the dislocation energy Ed and the
interfacial energy γ. What is the resulting value of γ?
G) The value for the interfacial energy calculated along the line in the previous questions is
higher than the actual value of the interfacial energy. Explain why.

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