American Board of Orthodontics (ABO) Practice Exam

Martensite is a phase of steel that forms when austenite is rapidly cooled (quenched), resulting in a transformation that significantly alters its mechanical properties. Stiffness is a measure of a material's resistance to deformation, and it is often associated with the modulus of elasticity.

Martensite is characterized by its high strength and hardness. However, it typically has a lower stiffness compared to austenite due to its more brittle nature following the transformation process. This difference arises because austenite, being the face-centered cubic (FCC) structure, tends to exhibit greater ductility and a more uniform distribution of plastic deformation under stress, allowing for higher stiffness in comparison to martensite, which has a body-centered tetragonal (BCT) structure that is less capable of distributing stress.

Understanding the mechanical behavior of these phases is crucial in materials science and engineering, particularly in applications where certain mechanical properties are desired for performance and durability. In summary, while martensite is stronger and harder than austenite, its stiffness does not exceed that of austenite.