Observations of Structural and Hardness Changes During the Repeated Bending Fatigue in Cu-6.0wt% Al Alloy

Abstract

Various changes in structure and in hardness of Cu-6.0wt% Al alloy at different stages of repeated bending fatigue test were studied by hardness test and by both micro-and electron microscopic observations.The experimental results are summarized as follows:(1) Irrespective of amplitude whether of high or low stress, the initial formation of slip bands are observed first during the stress cycling, and they are all of homogeneous slip.(2) After the appearance of slip bands, rippling phenomena of slip bands are observed and the phenomenon is remarkable in high stress amplitude.(3) After the formation of rippling bands, the intrusion and extrusion are observed principally along the grain boundaries in low stress amplitude, but in high stress amplitude, they come out irrespective of grain boundaries and slip bands.(4) The crack occurs initially along the grain boundaries in low stress amplitude, In high stress amplitude, they are observed both in the interior and along the grain boundaries.(5) The hardness of the specimens increase with increase in stress cycling numbers and the maximum hardness is obtained around the fractured area.