This is a interesting question, and the answer can not be clear. The titanium alloys are sensitive to surface integrity and the key or important factor is the surface roughness and thichness of parts. Ti-6Al-4V can be employed to manufactue compressor blades of engine and link joints in aircraft. For compressor blades, the thichness and surface roughness are factors which should be reviewed when choosing coverage. And in Specification of shot peening for aeronautical parts which I proposed, the coverage of parts of Ti-6Al-4V should not exceed 400% when shot peening new parts, and the times of repairing and overhauling is less than 4 and the coverage of each repairing and overhauling is not large than 200%.
I hope it can be useful because our investigation of shot peening of Ti-6Al-4V illustrates sensitiveness of surface integrity to fatigue and the strehgth of Ti-6Al-4V is not high compared to high strength steels, so my advice is a less coverage will be benifical to fatigue.
