FATIGUE FRACTOGRAPHS FOR BUTT-WELDED JOINTS OF A5083 ALUMINUM ALLOY.

A fractographic study has been performed on fatigue fractured butt-welded joints of an aluminum alloy, frequently used for low temperature applications. The area fraction of crystallographic facets, which takes the maximum in the lower range of stress intensity factor, DELTA K, decreased monotonically with an increase in DELTA K, and became zero at DELTA K of approximately 9 MPa m**1**/**2. The tendency of this evolution was found to be the same, irrespective of base metal or weld metal, as well as for the position of the facet which could be near or deep under the specimen surface. For higher values of DELTA K, the coverage of the striation facets became predominant, and the striation spacing was linearly correlated with DELTA K on log-log co-ordinates regardless of the metallurgical differences. The crack plane and propagation direction indicated that the striation formation mechanism could be explained by the model proposed R. M. Pelloux.