Scanning Atomic-Force Microscopy on Initiation and Growth Behavior of Fatigue Slip-Bands in α-Brass [chapter]

Y Nakai, T Kusukawa, N Hayashi
Fatigue and Fracture Mechanics: 32nd Volume  
Slip-band formation and fatigue crack-initiation processes in α-brass were observed by means of atomic force microscopy (AFM), and the effects of the grain size and the stress amplitude were discussed. In a fine grain material, fatigue cracks were initiated only from the slip-bands. In a coarse grain material, however, they were initiated either from the slip-bands or the grain boundaries. The depth of an intrusion drastically increased with its outgrowth to a crack, and with coalescence of
more » ... coalescence of cracks, the width of cracks increased rapidly. The depth of an intrusion increased with the number of loading cycles, and when the depth reaches a critical value, a transgranular crack was initiated from the intrusion. The critical value was given as a function of the slip-band angle relative to the stress axis. From the AFM observations, it was found that the critical value of the slip distance was independent of the slip-band angle relative to the stress axis, the stress amplitude, and the grain-size. For crack-initiations from grain boundaries, however, the value of the grain boundary depth at the crack initiation was not a unique function of the grain boundary angle relative to the stress axis.
doi:10.1520/stp10587s fatcat:iykpquwot5hnfoz5de2ace7l5q