Metals yield at a stress much lower than those calculated on the basis of their bond strength alone. This is explained by the presence of defects. Identify the principal defects responsible for this observation.
A)Grain Boundaries
B)Interstitial Metal Atoms
C)Vacancies
D)Dislocations
Noted.
dislocation
Please do not answer this post..... It is a part of the MIT edx curriculum and the poster and anyone who uses this information is in violation of the honor code. Thank you :)
The principal defects responsible for metals yielding at a stress lower than calculated based on their bond strength alone are grain boundaries, interstitial metal atoms, vacancies, and dislocations.
A) Grain boundaries are interfaces between individual crystals, also known as grains, in a polycrystalline metal. They occur due to variations in crystal orientation from one grain to another. Grain boundaries limit the movement and deformation of dislocations, leading to lower yield strength.
B) Interstitial metal atoms can be present in the interstitial sites between the regular lattice atoms of a metal. These atoms can cause disruptions of the crystal lattice and hinder the motion of dislocations, resulting in reduced yield strength.
C) Vacancies are empty spaces or missing atoms in the crystal lattice. These vacancies can act as localized stress concentrators or trapping sites for dislocations, making it easier for the metal to yield at lower stresses.
D) Dislocations are line defects in the crystal lattice where there is a mismatch in the regular arrangement of atoms. These dislocations can move within the lattice under the application of stress, allowing for plastic deformation. The presence of dislocations decreases the strength of the metal and causes it to yield at lower stresses.
Therefore, the principal defects responsible for the observation of metals yielding at a stress lower than their bond strength alone are grain boundaries, interstitial metal atoms, vacancies, and dislocations.