Kinetics and Microstructural Control

· The lattice orientation of a "lens" of bcc martensite forming in the fcc austenite matrix is illustrated.
· The change in crystallography and the need to minimize elastic strain energy give an interface that is {111} with respect to the austenite but {110} with respect to the bcc martensite.
· As a result of the transition the <001> direction in the austenite is parallel to the <111> direction in the martensite.

From: Ashby & Jones, "Engineering Materials," Pergamon (1986)