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Difficulty: MediumAlloys: Classification, Compositions, Physical Properties, and Uses

Alloying pure copper with zinc to produce brass enhances its mechanical hardness and tensile strength, but leads to a decrease in its electrical conductivity compared to pure copper.

Answer: Answer

Answer

True. Alloying copper with zinc to form brass increases mechanical strength and hardness via lattice distortion, but decreases electrical conductivity due to increased electron scattering.
The statement accurately reflects physical metallurgy principles. Foreign zinc atoms create strain fields in the copper lattice that block dislocation movement (increasing hardness), while simultaneously disrupting the periodic potential required for efficient electron transport (decreasing electrical conductivity).

Step-by-Step Solution

1
Analyze the composition and structure of brass.
Brass is a substitutional alloy formed by dissolving zinc atoms into the copper metallic lattice.
Understanding the atomic mixture establishes how foreign atoms fit into the primary metal matrix.
2
Evaluate the effect of foreign zinc atoms on mechanical properties.
Zinc atoms differ in size from copper atoms, causing localized lattice distortion that impedes dislocation motion.
Restricting the slipping of crystal planes increases the alloy's hardness and tensile strength compared to pure copper.
3
Evaluate the effect of lattice distortion on electrical conductivity.
The loss of periodic lattice symmetry increases the scattering of free conduction electrons.
Increased electron scattering reduces the mean free path of charge carriers, lowering overall electrical conductivity relative to pure copper.

Key Concept

Influence of alloying on mechanical hardness and electrical conductivity
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Topics

Alloys: Classification, Compositions, Physical Properties, and Uses

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