Increase in Fatigue Life during Cyclic Torsion of 6060 T6 and T64 Aluminium Alloy Samples after Vibratory Shot Peening

Abstract

The paper analyses the influence of strengthening treatment by vibratory shot peening on the fatigue life of samples made of 6060 aluminium alloy. Samples made of material in the T6 and T64 conditions were selected for the analyses. The analysed materials were strengthened using vibratory shot peening for 1 and 10 minutes. Vibration strengthening showed that fatigue life was increased in all cases. For aluminium in the T6 condition, the increase in durability increases with the extension of the strengthening process, and for aluminium in the T64 condition, a short strengthening process results in a significant increase in fatigue life, while further strengthening not only does not improve durability but even worsens it. The fatigue crack surfaces in the analysed cases were also observed and compared. Origin, fatigue cracking zone, and instantaneous zone have been distinguished. This analysis showed that T6/T64 machining and strengthening by 1/10 minute vibratory shot peening have different effects on the fatigue life and the structure of fatigue fractures. It has been shown that the strong strengthening of the plastic aluminium alloy in the T64 condition causes the formation of something like a structural notch on the material’s surface.