Temper Embrittlernent by Phosphorus and Fracture Behavior

Abstract

Temper embrittlement and fracture behavior of Fe-C and Fe-C-Ni-Cr alloys doped with P were studied by means of grain boundary etching technique, Charpy impact tests, and low temperature tensile tests.
Grain boundary etching behavior with respect to aging time seems to correspond to the cementite precipitation at the grain boundaries together with the change of the grain boundary concentration of P. Temper embrittlement does not occur only by the grain boundary segregation of P, but needs the coexistence of alloying elements such as Ni or Cr.
Brittle fracture in temper embrittled alloys is initiated by the formation of grain boundary cracks followed by the crack propagation without arresting. Therefore, Griffith's crack such as a pearlite colony crack is not assumed to exist in the fracture of temper embrittled alloys.