Which structure is formed directly as a result of quenching steel?

Which structure is formed directly as a result of quenching steel?

• A. Martensite
• B. Ferrite
• C. Pearlite
• D. Cementite

Answer: (A)

Rapid cooling from the austenite region drives a diffusionless transformation to martensite. When steel is quenched, carbon can’t diffuse out quickly enough and the crystal lattice shifts into a distorted form, creating martensite, a hard and brittle phase that forms directly from the austenite without long-range atomic rearrangement. The other structures—ferrite, pearlite, and cementite—depend on diffusion and slower cooling through specific temperatures, so they don’t form directly during a fast quench. Ferrite and cementite arise from diffusion-controlled transformations, and pearlite is a layered mixture of ferrite and cementite that develops during the eutectoid transformation as cooling proceeds more slowly.

Rapid cooling from the austenite region drives a diffusionless transformation to martensite. When steel is quenched, carbon can’t diffuse out quickly enough and the crystal lattice shifts into a distorted form, creating martensite, a hard and brittle phase that forms directly from the austenite without long-range atomic rearrangement. The other structures—ferrite, pearlite, and cementite—depend on diffusion and slower cooling through specific temperatures, so they don’t form directly during a fast quench. Ferrite and cementite arise from diffusion-controlled transformations, and pearlite is a layered mixture of ferrite and cementite that develops during the eutectoid transformation as cooling proceeds more slowly.