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Select any two from (i), (ii) or (iii) below and explain: (i) The impact of a dislocation in crystal structures - Leaving Cert Engineering - Question c - 2021
Question c
Select any two from (i), (ii) or (iii) below and explain: (i) The impact of a dislocation in crystal structures. (ii) The possible corrosive effects of the environ... show full transcript
Worked Solution & Example Answer:Select any two from (i), (ii) or (iii) below and explain: (i) The impact of a dislocation in crystal structures - Leaving Cert Engineering - Question c - 2021
Step 1
The impact of a dislocation in crystal structures.
Answer
Dislocations play a crucial role in the mechanical properties of crystalline materials. They can move through the crystal lattice, particularly under shear stress, influencing the material's strength and malleability.
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Dislocation Movement: Dislocations can travel towards grain boundaries during deformation. Fine-grained metals exhibit greater strength and hardness compared to coarse-grained metals due to the presence of more grain boundaries that impede slip.
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Malleability Promotion: The presence of dislocations enhances the material's malleability, allowing it to deform plastically. This is crucial in applications requiring complex shaping processes.
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Heat Treatment Effects: Heat treatments can affect dislocation density. Processes like annealing can reduce dislocation density by allowing recovery and recrystallization, thereby improving ductility.
Step 2
The possible corrosive effects of the environment on metal objects.
Answer
Corrosion is a significant issue affecting metal structures and objects, leading to deterioration and failure.
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Ferrous Metals and Rust: Ferrous metals, such as steel, are prone to rusting when exposed to moisture and oxygen, which can lead to structural failures.
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Oxide Layer Formation: Some metals may develop an oxide layer that protects them. For example, aluminum can form a dull oxide layer, which might not always be protective, varying with environmental conditions.
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Electrochemical Reactions: The presence of seawater or acidic conditions can initiate electrochemical corrosion reactions, especially affecting reactive metals like copper or zinc, and may cause accelerated degradation in metals used in marine environments.