Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Effect of specimen orientation and extrusion welds on the fatigue life of an AA6063 alloy



Nicholas Nanninga


The effect of specimen orientation and extrusion seam welds on the fatigue life of specimens milled from a hollow AA6063 alloy extrusion profile have been characterized in the form of S-N curves. The fatigue behavior of the fully recrystallized AA6063 alloy reported here is compared to previously reported results on a partially recrystallized AA6082 extruded alloy [Nanninga N, White C, Furu T, Anderson O, Dickson R. Effect of orientation and extrusion welds on the fatigue life of an Al-Mg-Si-Mn alloy. Int J Fatigue 2008;30(9):1569-1578]. Specimen orientation with respect to the extrusion direction has a large effect on fatigue life, and is attributed to the orientation of extrusion die lines. Transverse specimens exhibit only a fraction of the high cycle fatigue life exhibited by longitudinal specimens. The presence of seam and/or charge welds, oriented both longitudinal and transverse to the loading direction may also reduce the fatigue life. The effects of these welds, however, are not as significant as the effects of orientation alone and appear to be related to increased surface roughness. The variations in fatigue life are explained by surface roughness and variations in microstructure. Grain boundary separation was the primary mechanism of fatigue crack initiation in this study and results from Auger and TEM analyses suggest that localized strain in precipitate free zones may assist in this behavior.
International Journal of Fatigue


Seam weld, extrusion, AA6063, fatigue, auger, grain boundary


Nanninga, N. (2009), Effect of specimen orientation and extrusion welds on the fatigue life of an AA6063 alloy, International Journal of Fatigue (Accessed June 21, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created February 13, 2009, Updated February 19, 2017