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110年 - 110 國立清華大學碩士班考試入學試題_工程與系統科學系/甲組:物理冶金#104981
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1. Fig. 1 shows a
slip plane of fec crystal containing an edge dislocation.
(e)The strength of an fec metal can be increased by controlling the stacking fault energy. Discuss the strengthening mechanism. (5%)
相關申論題
(a) Write down the Burgers vector of the dislocation. (2%)
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(b) What is the direction of [u1 V1w1]. (3%)
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(c) Describe the position of the dislocation including direction of the dislocation line and the Burgers vector in Fig. 1. (5%)
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(d) In fec metals, the dislocations are usually dissociated into an extended dislocation, containing two partial dislocations and a stacking fault. Fig. 2 shows an extended dislocation in fcc lattice. Describe the position of the partial dislocation including the direction of dislocation line and Burgers vectors. (5%)
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(a) Identify whether you think the crystal is FCC or BCC (5%), and
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(b) explain briefly why in each case (15%).
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(a) There is a condition for necking for a true stress-strain curve called Considere's criterion. Derive the Considere's criterion for a true stress-strain curve satisfied a = Kεn, where o is the true stress, s is the true strain, n is the strain hardening exponent, and K is the strength coefficient.(5%)
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(b) Discuss why the strain hardening exponent decreascs with increasing stacking fault energy, as shown in the table below (5%)
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(c)For fcc and bcc metals, there are different temperature dependence on the flow stress components, as shown in Figs. 6 and 7. Use the Considere's criterion to explain the reasons that cause this difference. (10%)
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(a) Refer to Fig. 8 above, and consider the three temperature histories shown. If you are trying to design a steel that best takes advantage of dislocation interactions with a second phase (i.e, strength controlled by bowing), which path is best and why? (10%)
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相關試卷
110年 - 110 國立清華大學碩士班考試入學試題_工程與系統科學系/甲組:物理冶金#104981
110年 · #104981
slip plane of fec crystal containing an edge dislocation.
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slip plane of fec crystal containing an edge dislocation.