Temperature dependence of transgranular fatigue crack resistance in interstitial-free steel and Fe-C steels with supersaturated carbon: Effects of dynamic strain aging and dynamic precipitation

Tension tests at different temperatures were conducted for two ferritic steels: Fe-0.017C with 0.017% solute carbon content and interstitial-free (IF) steels. It is verified the occurrence of dynamic strain aging (DSA) in Fe-0.017C at high temperatures. Tension tests for the Fe-0.017C, following corresponding heating treatments, demonstrated the transition process of dynamic precipitation from under-aging to over-aging. Moreover, the threshold stress intensity factor ranges (ΔKth) of a small crack for these two steels both decrease with temperature growth. However, the ΔKth of Fe-0.017C was always larger than that of IF steel owing to solid solution hardening and DSA at 293 and 333 K and roughness-induced crack closure and precipitation hardening at 433 K.