Evolution mechanism of surface nano-crystallization of tungsten-copper alloys

• A nanostructured surface layer was fabricated by supersonic fine particles bombarding.
• The thickness of nano-layer was directly depending upon the treatment duration.
• Grain refinement process involved internal defects proliferation of Wand plastic deformation of Cu.

A nanostructure surface layer was fabricated on CuW70 alloy by supersonic fine particles bombarding (SFPB) technology. The microstructure features of the surface layer were characterized by using XRD, SEM, TEM observations. The results show that severe plastic deformation was produced on the surface of SFPB-treated CuW70 alloy, a part of W particles were fragmented and become smaller on the surface, while the Cu particles only exhibit deformation. The thickness of nanostructure surface layer increased depending upon the treatment duration, the well technology was shot peening 60 min, in this case, the thickness up to 21 µm, the grain refinement process of CuW70 alloy involved internal defects proliferation, particles deformation and break up, grain refining of W, and strong plastic deformation of Cu bonding phase. Finally, the random orientation of nano-crystal was formed on the surface.