From 910 C to 1390 C, iron has which crystal structure?

From 910 C to 1390 C, iron has which crystal structure?

• A. BCC
• B. HCP
• C. FCC
• D. Simple cubic

Answer: (C)

Iron’s crystal structure changes with temperature. Below about 912°C it exists as ferrite with a body-centered cubic (BCC) lattice. Once you heat past that point, iron reorganizes into a face-centered cubic (FCC) lattice, known as austenite, and this FCC form remains stable roughly from 912°C up to about 1394°C. Beyond that, delta-iron with a BCC structure forms again before melting at around 1538°C. So in the range from about 910°C to 1390°C, the crystal structure is FCC. This FCC arrangement reflects iron’s ability to dissolve more carbon and influences how heat treatment and alloying behave. The other structures aren’t present in that temperature window: BCC appears at lower temperatures, HCP is not a stable form for iron under normal conditions, and simple cubic is not a phase iron adopts.

Iron’s crystal structure changes with temperature. Below about 912°C it exists as ferrite with a body-centered cubic (BCC) lattice. Once you heat past that point, iron reorganizes into a face-centered cubic (FCC) lattice, known as austenite, and this FCC form remains stable roughly from 912°C up to about 1394°C. Beyond that, delta-iron with a BCC structure forms again before melting at around 1538°C. So in the range from about 910°C to 1390°C, the crystal structure is FCC. This FCC arrangement reflects iron’s ability to dissolve more carbon and influences how heat treatment and alloying behave. The other structures aren’t present in that temperature window: BCC appears at lower temperatures, HCP is not a stable form for iron under normal conditions, and simple cubic is not a phase iron adopts.