Abstract: A mechanism of intergranular fracture of as-quenched martensite in high carbon steels has been proposed.When coarse grains of austenite transform to martensite,the grain plays a role of the unit of volume dilation,inhomogeneous strains necessarily produce and local microscop- ic stress concentrations create at grain boundaries.This reduces the intergration of the grains, sometimes intergranular cracks may produce.Under the action of first kind hardening stress or external force,the intergranular cracks propagated along the grain boundaries will form. This results in the candy-like fracture.

Key words: as-quench martensite, intergranular fracture, inhomogeneous strain