晶体中若有较多的线缺陷和面缺陷,其强度会明显提高，产生这一现象的原因是什么？

你好，线缺陷和面缺陷破坏了晶体的完整性，增加了位错运动的阻力，所以强度和硬度会增加。冷加工变形增加了位错密度，产生较多线缺陷，即产生加工硬化现象。细化晶粒增加了晶界，产生较多面缺陷，即产生细晶强化。

 Influence for resistivity: the resistance of metal comes from the scattering of ion to electron. In the intact crystal, the electron basically moves in the uniform electric field, but in the crystal with point defect, the periodicity of the lattice in the defect area is destroyed, and the electric field changes rapidly, so the electron is strongly scattered and the resistivity of the crystal increases.Influence for plastic deformation: In order to elongate or flatten a crystal, we need exert external force to break the metal bond between atoms, which requires huge energy. As a result, a large number of cracks and even fracture will be generated inside it However, for a crystal with dislocations, this will become very simple, a large number of dislocations slip towards the stress direction, enough to make the material shape change without damage. So, the essence of deformation and the plastic deformation of the material comes from dislocations.