What is the space lattice of martenside?

What is the space lattice of martenside?

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

Answer: (A)

Martensite forms when austenite (the fcc phase of iron) is quenched so quickly that the transformation happens without diffusion. The carbon atoms trapped in the lattice resist the original cubic spacing, causing a coordinated distortion that elongates one axis. This produces a tetragonal unit cell with centering, i.e., a body-centered tetragonal lattice. The c-axis becomes longer than the a- and b-axes, giving the BCT structure that characterizes martensite. The other lattices—fcc, bcc, or a simple tetragonal—don’t reflect this diffusionless distortion and centering pattern.

Martensite forms when austenite (the fcc phase of iron) is quenched so quickly that the transformation happens without diffusion. The carbon atoms trapped in the lattice resist the original cubic spacing, causing a coordinated distortion that elongates one axis. This produces a tetragonal unit cell with centering, i.e., a body-centered tetragonal lattice. The c-axis becomes longer than the a- and b-axes, giving the BCT structure that characterizes martensite. The other lattices—fcc, bcc, or a simple tetragonal—don’t reflect this diffusionless distortion and centering pattern.