At what temperature does ferromagnetic alpha iron transition into paramagnetic alpha iron _______________?
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Answer: A. 770°C
Explanation
Ferromagnetic alpha iron, or ferrite, maintains strong magnetic attraction at ambient and moderate industrial temperatures. When heated to approximately 770 degrees Celsius, thermal energy disrupts the alignment of atomic magnetic moments within the lattice. This critical transformation point is known as the Curie temperature, above which ferrite becomes paramagnetic. The Curie point marks a second-order phase transition where permanent magnetic properties disappear without changing the crystal structure. Alpha iron retains its body-centered cubic crystal lattice across the magnetic transition boundary at 770 degrees Celsius. Further heating of alpha iron to 910 degrees Celsius triggers a crystallographic transformation into face-centered cubic austenite.
Option B of 910 degrees Celsius is the temperature where alpha iron transforms structurally into gamma iron austenite, not the magnetic Curie point. Option C of 1050 degrees Celsius represents high-temperature austenitizing ranges rather than the magnetic transition. Options D and E refer broadly to recrystallization temperatures, which are distinct from the specific Curie magnetic transition.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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