The yield point elongation phenomenon observed in annealed low-carbon steels is attributed to the presence of which element?
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Answer: B. Carbon
Explanation
Yield point elongation in low carbon steels is caused by interstitial carbon atoms pinning dislocations. Cottrell atmospheres of carbon atoms lock dislocations requiring higher initial stress to initiate yielding. Once dislocations break free from carbon atom atmospheres, upper and lower yield points occur. Strain aging phenomena in annealed low carbon steels result from carbon and nitrogen atom diffusion. Dislocation dynamics dictate the plastic deformation behavior of crystalline metallic materials. Tempering and annealing processes alter interstitial atom distributions within steel microstructures.
Automotive stamping sheets undergo temper rolling to eliminate yield point elongation and surface fluting. Metallurgical quality control monitors carbon content strictly to achieve desired sheet metal formability. Structural steel specifications account for yield point characteristics during tensile strength testing. Silicon is primarily a deoxidizer and solid solution strengthener rather than a dislocation pinner. Phosphorous increases steel strength and hardness but does not cause typical yield point elongation. Chromium forms carbides and improves corrosion resistance without causing Cottrell locking phenomena.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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