Metallurgical aspects and closure maps of fatigue crack growth of alloy steels .1. Effect of second phase on crack closure

The role of second phase in AISI 4330 steel on the fatigue crack closure has been investigated. The mixed microstructure of upper bainite-martensite shows a better fatigue crack growth (FCG) resistance in the near threshold region than the fully martensite structure steel due to increase in roughness induced closure stress.