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Distinguish clearly between a substitutional solid solution and an interstitial solid solution - Leaving Cert Engineering - Question c - 2014
Question c
Distinguish clearly between a substitutional solid solution and an interstitial solid solution. Describe one effect of the movement of the line defect shown below.
Worked Solution & Example Answer:Distinguish clearly between a substitutional solid solution and an interstitial solid solution - Leaving Cert Engineering - Question c - 2014
Step 1
Distinguish clearly between a substitutional solid solution and an interstitial solid solution.
Answer
A substitutional solid solution occurs when an atom of a different element replaces a parent atom in the crystal lattice. This replacement can happen if the atoms are of similar sizes, allowing for minimal distortion in the lattice structure. For instance, in a copper-nickel alloy, copper atoms may be substituted by nickel atoms without significantly altering the overall structure.
In contrast, an interstitial solid solution forms when smaller atoms occupy the interstitial spaces between the larger atoms of the parent metal. This insertion causes distortion due to the size difference and creates compressive stresses in the lattice. The presence of interstitial atoms can enhance the material's strength since dislocations require higher stress to move.
Step 2
Describe one effect of the movement of the line defect shown below.
Answer
The diagram represents the movement of a dislocation typically caused by shear forces. As these forces are applied, the dislocation moves to the adjacent line, which can subsequently shift toward the grain boundary. This movement of dislocations allows the material to deform, facilitating plastic deformation under stress. Moreover, the presence of dislocations is crucial in influencing the mechanical properties of the material, as they can significantly impact its strength and ductility.