The lattice type of martensite is best described as which?

The lattice type of martensite is best described as which?

• A. Body-centered tetragonal
• B. Face-centered cubic
• C. Body-centered cubic
• D. Simple cubic

Answer: (A)

Martensite forms through a diffusionless, rapid transformation of austenite, and the carbon atoms that remain in interstitial sites distort the lattice as it rearranges. This distortion takes a body-centered lattice and elongates one axis, giving a tetragonal symmetry. The result is a body-centered tetragonal structure, which is why martensite is described that way. The other options describe the parent phase or other simple lattice types that don’t account for the carbon-induced distortion seen in martensite—fcc is the austenite structure, while plain cubic forms don’t capture the tetragonal distortion produced by carbon—so they don’t fit the observed martensite crystal lattice.

Martensite forms through a diffusionless, rapid transformation of austenite, and the carbon atoms that remain in interstitial sites distort the lattice as it rearranges. This distortion takes a body-centered lattice and elongates one axis, giving a tetragonal symmetry. The result is a body-centered tetragonal structure, which is why martensite is described that way. The other options describe the parent phase or other simple lattice types that don’t account for the carbon-induced distortion seen in martensite—fcc is the austenite structure, while plain cubic forms don’t capture the tetragonal distortion produced by carbon—so they don’t fit the observed martensite crystal lattice.