What is the mechanism of plastic deformation in non-crystalline ceramics?
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A.
Twinning
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B.
Slip
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C.
Viscous flow
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D.
Cross-slip
Correct Answer:
C. Viscous flow
Explanation:
The correct mechanism for plastic deformation in non-crystalline ceramics is viscous flow. Unlike crystalline materials, non-crystalline or amorphous ceramics, such as glass, lack a long-range periodic atomic structure. This absence of an ordered lattice means there are no defined crystallographic planes or directions to support deformation through slip or twinning. Instead, when stress is applied, particularly at elevated temperatures, the atomic bonds break and reform in a continuous, disorganized manner, allowing the material to flow. The ease of this deformation is governed by the material's viscosity, which represents its resistance to flow and typically decreases as temperature increases. In contrast, mechanisms like slip and twinning require the specific geometric arrangements found only in crystalline structures.
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