Correlation between grain orientation and fretting damage mechanism in a cold-rolled TB8 titanium alloy

Ti alloys are widely used for aerospace fasteners. However, fasteners made of Ti alloys with a poor wear resistance, are often exposed to harsh conditions of fretting damage, which leads to wear and cracks initiation. Thus, the interplay relationship between fretting damage and crystallographic orientation should be deeply demonstrated. In this work, a cold-rolled Ti alloy is used to investigate the correlation between crystallographic orientation and fretting damage. The results show that the wear volume in the case that the fretting direction is perpendicular to the grain elongation direction, is only 1/3 of that in the parallel case. This can be attributed to stress-induced ω phase transformation in nano-grain layer, an existence of transition layer and stress-induced twinning in substrate. These can avoid crack initiation caused by stress concentration at the nano-grain boundaries as the parallel case. This work can provide sufficient information for designing fretting damage-resistant Ti alloys.