课程名称︰物理冶金 课程性质︰必修 课程教师︰杨哲人 开课学院：工学院 开课系所︰材料系 考试日期（年月日）︰102.11.21 考试时限（分钟）：180 min 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1.(a) In an actual crystal, because of the more complex spatial arrangement of atoms, the dislocation are complicated and often difficult to vasualize. However, two terms can be used to completely describe the dislocation. Point out these two terms. (2%) (b) Explain why the intersection of two perpendicular screw dislocations can lead to the production of a row of vacancies. (2%) (c) What is the dark-field image of transmission electron microcopy ? (2%) 2.(a) It is possible to make a dislocation loop all of whose segment are pure screw dislocation. Briefly explain why. (b) Explain how to create a screw-compoment kink on an edge dislocation. (4%) 3.(a) Construct a 100 standard stereographic projection of a cubic crystal. In this projection, show the great circles for {100} and {110} planes, and the poles for {100}, {110} and {111} planes. (b) Use the stereographic projection construct in Problem 2(a) to consider the following procedure. Rotate 100 standard stereographic projection about its north-south axis to obtain a 1 0 1 standard projection, and draw a corresponding figure showing the poles of {1 0 0}, {1 1 0} and {1 1 1} planes whose zone axis is [1 0 1]. In this case, what is the north-south axis for rotation ? How much angle is rotated along this axis ? (c) On the assumption that the electron beam of a transmission electron microscope is parallel to [1 0 1] in a simple cublc (cubic-P) crystal, draw a sketch of electron fiddraction pattern (according to a proportional scale). (10%) 4.(a) Explain how to create the scondary electrons and characteristic X-rays, during the interaction of a high-energy beam of electrons and a metallic specimen. (b) Briefly explain why (1 1 0) plane is not a reflection plane in FCC metals. (5%) 5. Claculate the magnitudes of 1/6 [-1 0 1 3] in terms of lattice parameters, a and c of hexagonal crystal. (5%) 6. From X-ray diffractometry of a FCC metal, point out the indices of the planes, which are connected with the first seven respective diffraction peaks (from low angle to high angle). (5%) 7. A pure metal crystal belongs to the cubic crystal system. From X-ray diffractometry measurement, it is known that the first seven diffraction peaks occurs at sin^2(θ) = 0.137, 0.275 ,0.412, 0.551, 0.688, 0.826, 0.962. What is the Bravais lattice ? Calculate and answer the question. (5%) 8. An intrinsic stacking fault in FCC metals can occur by condensation of vacancies on a (-1 1 1) plane. The partial dislocation loop, surrounding the stacking fault, forms. Give the Burgers vector for this partial dislocation loop. Is this dislocation with pure edge, pure screw or mixed characteristic ? why ? (5%) 9. It has been well known that the stacking sequence of the close-packed plane (1 1 1) in the FCC metals is ABCABC...... If the movement of an atom on a B plane by a ahear 1/2 [-2 1 1] relative to the neighboring C plane, can this atom remain in the B plane stacking ? Why ? Give your reason. (5%) 10. The schematic diagram is for representation of the DEebye-Scherrer or power camera method. In this powder method, the wavelength λ remains constant and a variation of Bragg's angle θ is obtained. Specimen is assumed to be simple cubic and the spacing between (h k l) planes is can be expressed as d(hkl) = a / (N^1/2) where N = h^2 + k^2 + l^2, and a is lattice constant. Derive a formula to relate Bragg's angle θ with N value. (5%) 11.(a) What kind of stress field is associated with the screw dislocation ? (b) Explain why a dislocation cannot end inside a crystal. (5%) 12. The force is extered on a straight screw dislocation (with Burgers vector, b) by a ahear stress τ, which is parallel to the dislocation line along the slip plane as shown in the following figure. Assume that L is the length of the dislocation; Δx is the dislocation moving along slip plane through a distance; A is the area of the slip plane. Calculate the force per unit length on the dislocation, and also indicate the direction of this force. (5%) (附上讲义75页第一个图) 13. In the above figure, take the orientation of the screw dislocation snd than use Burgers circuit to determine the Burgers vector. (请画在上图) Is it right-hand or left-hand screw dislocation ? What is the relationship between the Burgers vector and the orientation of this dislocation ? (5%) 14.(a) When a dislocation moves on its slip plane from one side of a crystal to the other, what information can be specified by its Burgers vector ? (b) What is an extended dislocation ? (5%) 15. Electron diffraction patterns represent the information of a reciprocal lattice for a corresponding real lattice. Give two key points for the relationship between reciprocal lattice and real lattice. (5%) 16. Use the Burgers vector notation for dislocation reactions to illustrate that in an FCC metal a total dislocation with Burgers vector 1/2 [1 1 0] breaks down into a pair of Shockley partial dislocations on (1 -1 1) planes. (5%) 17. Repeat the above question for that in an HCP metal a total dislocation with Burgers vector 1/3 [2 -1 -1 0] breaks down into a pair of Shockley partial dislocations on the basal plane. (5%) 18. The srain energy of a dislocation normally varies as the square of its Burgers vector. Show that on the basal plane in a HCP crystal the disslocation of a total dislocation in the above question is energetically feasible. (Assume that the stacking fault energy is negligible.) (5%) 19. The following figure shows two pure screw dislocations, one of which contains a kink and the other a jog. Take the positive direction of the lines as shown by the arrows. Both the kinked segments and the jogged segment are pure edge dislocations. (a) Redraw the above kinked dislocation and ahow on your drawing the location of the extra plane of atoms for both kinked segments. (b) Repeat (a) for the jogged dislocation. (5%) (附讲义72页下面、73页上面的图) --

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