Microstructure and Mechanical Properties of Silver-Loaded Layer on Surface of TC4 Alloy Prepared by Friction Stir Processing

Friction stir processing was utilized to prepare silver-loaded layer on the surface of Ti-6Al-4V (TC4) titanium alloy successfully. The morphology, distribution and influence on the mechanical properties of silver in the silver-loaded layer were studied. The results show that a silver-loaded layer of 700 μm in thickness was successfully fabricated. A large number of silver nanocrystallines with 10 nm in average diameter were observed in the top surface of silver-loaded layer due to mechanical nanocrystallization resulted from strong stirring shear force. In the sub-surface of silver-loaded layer, silver particles precipitated and formed a solid bonding with the matrix and free particles would barely appear in service. Uniformly distributed silver particles made the surface nanohardness of the silver-loaded layer about 30% higher than that of the silver-free zone, while it had little effect on the elastic modulus of the matrix.