For good electrical and thermal conductors, a pure metal under well annealing co
ID: 2305933 • Letter: F
Question
For good electrical and thermal conductors, a pure metal under well annealing condition is the best choice because of decreased impurity and vacancy scatterings to electron movement.
True ______ or False ______
5. For a polycrystalline material, the atomic diffusion rate along grain boundaries is the same as the rate of bulk diffusion (i.e. bulk diffusion is the atomic diffusion inside a crystalline grain) because the same atoms have the same diffusivity throughout the material.
True ______ or False ______
6. The surface morphology of a brittle fracture is characterized with dimples.
True ______ or False ______
7. For heat treatable aluminum alloys, their early precipitates are coherent with the Al matrix, introduce large elastic strain zones as compared to their physical sizes, and contribute more strength to an alloy.
True ______ or False ______
8. Al-Li alloys are one new generation of light-weight alloys. However, binary Al-Li alloys are often brittle because their precipitates, the coherent superlattice phase d¢(Al3Li), cause the localization of dislocation slip, which further results in a loss in ductility and fracture toughness.
True ______ or False ______
9. The plastic deformation at room or low temperatures is a result of orientated atomic diffusion while the plastic deformation at high temperatures is due to dislocation sliding.
True ______ or False ______
10. For Fe, martensitic transformation causes a sudden volumetric expansion, if not controlled carefully, often resulting in materials rupture. Therefore, low-carbon steels generally have better weldability than high-carbon steels because the former seldom produce martensite under air or low cooling-rate conditions but the latter can easily transform to martensite.
True ______ or False ______
Explanation / Answer
No, it can not be a best choice. For a good conducting metal it should be large number of free electrons and their moment. If we decrease the impurities and vacancy they can affact on electrical properties of metal.
We have already seen in the semiconductors, while we are doping the impurity, value of current goes increases.
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