Microstructure evolution and mechanical behavior of severe shot peened commercially pure titanium

• Severe shot peened CP titanium materials have nanograined structure on the surface.
• The nanograins range is between 25 and 80 nm due to plastic deformation rate.
• The nanohardness increase is approximately 1.5 times with compared to bulk.
• Elastic modulus raises approximately 2 times with compared to bulk.

Severe plastic deformation methods such as equal channel angular pressing (ECAP), high pressure torsion (HPT) and constrained groove pressing (CGP) have been increased in importance due to superior mechanical properties evolution and nanostructured grains build up. Besides, severe shot peening has been using as a severe plastic deformation method in recent years and applied converting microstructure to nanostructure just below the surface. Not only enhancement of fatigue, fretting fatigue and corrosion strength of materials but also altering the surface microstructure gathers much interest for severe shot peening application. In this study, severe shot peening with different Almen intensities (A28–30, A30–32, A32–34, A34–36, C4–6, C6–8, C8–10) was performed on commercially pure (CP) titanium (grade 2) and the specimens surfaces were investigated according to Almen intensity (plastic deformation rate). Also mechanical properties such as hardness and elastic modulus have been investigated by performing nanoindentation tests. Results have shown the work hardened layer is approximately 160 μm and has nanograin size distributions with much higher nanohardness and elastic modulus with compared to those of inside the bulk material.