REVERSIBILITY AND HYSTERESIS OF MARTENSITIC TRANSFORMATIONS

The term martensitic is used for a diffusionless structural phase transformation beta --> alpha(M) which is associated with a considerable amount of lattice variant shear: gamma(beta-alpha) almost-equal-to 0.2. This reaction is defined as reversible if the reverse reaction alpha(M) --> beta faultlessly restores the original parent crystal-beta. Sets of factors are established which favour the reversible (or irreversible) mode. Hysteresis is due to lattice friction acting on the moving beta/alpha(m) transformation interfaces during a transformation cycle. It can vary by several orders of magnitude. Analogies are indicated between ferromagnetic and martensitic hysteresis.