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A microscopic image of the metal solidification process, dendritic growth, is shown - Leaving Cert Engineering - Question 5 - 2022
Question 5
A microscopic image of the metal solidification process, dendritic growth, is shown. (i) Describe, with the aid of diagrams, the process of dendritic growth. (ii) ... show full transcript
Worked Solution & Example Answer:A microscopic image of the metal solidification process, dendritic growth, is shown - Leaving Cert Engineering - Question 5 - 2022
Step 1
Describe, with the aid of diagrams, the process of dendritic growth.
Answer
Dendritic growth is a characteristic solidification pattern observed in metals as they cool and transition from liquid to solid.
As the metal reaches its cooling point, small particles begin to cool first and solidify in a specific pattern. This growth resembles tree branches, which is the origin of the term 'dendritic' derived from the Greek word 'dendron' meaning tree.
Diagram
Each small particle forms a crystal or grain, and these crystals grow together to form a solid. This interconnected growth leads to the formation of intricate patterns that improve mechanical strength and durability.
Step 2
Describe, with the aid of a diagram, any two crystal point defects which may occur during the solidification process.
Answer
During the solidification process, two common types of crystal point defects that can occur are:
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Substitute Defect: This defect occurs when foreign atoms replace the atoms of the parent lattice. This can affect the properties of the material significantly.
Diagram of Substitute Defect
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Vacancy Defect: This defect is characterized by the absence of an atom in the lattice, leaving a void which can disrupt the crystal structure.
Diagram of Vacancy Defect
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Interstitial Defect: This occurs when foreign atoms fit into the spaces between the parent atoms, affecting the density and stability of the structure.
Diagram of Interstitial Defect