Effect of initial microstructure on surface relief and fatigue crack initiation in AISI 410 ferritic-martensitic steel

BATISTA, M.N.; MARINELLI, M.C.; ALVAREZ-ARMAS, I.

FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Lugar: London; Año: 2019 vol. 42 p. 61 - 68

8756-758X

This work is focused on the effect of the initial tempered‐lath microstructureon the surface relief and nucleation of microstructurally short fatigue cracksdeveloped during low‐cycle fatigue tests of the ferritic‐martensitic AISI 410steel. Transmission and scanning electron microscopy as well as electronback‐scattered diffraction were used to study the surface‐damage evolution insmooth, cylindrical, notched specimens. Results from the electron back‐scattered diffraction analysis broaden the understanding of the processes ofnucleation of microstructurally short fatigue cracks in the initial tempered‐lath microstructure of AISI 410 ferritic‐martensitic steels. Results prove that during fatigue, microcracks nucleate mainly at high‐angle boundaries represented byblock subunit interfaces formed in this tempered microstructure. Besides, theprogress of fatigue cycling causes the reorientation of the {112} systemsto a direction more favourable to slip, giving rise to the formation of extrusions within the blocks and consequently the formation of microcracks.