Atomic-scale intermixing, amorphization and microstructural development in a multicomponent system subjected to surface severe plastic deformation

Al, Zr, Ni, Co, Fe and Cr were introduced into a Cu plate using ball collisions to fabricate a multicomponent composite layer. The application of severe plastic deformation induced by repeated ball collisions with the as-fabricated composite layer led to intermixing of the components and the formation of a surface alloyed layer on the Cu plate. The microstructural development of the surface alloyed layer was a function of the treatment time. After 1 h of treatment, an alternating laminated amorphous/crystalline composite structure with a mean lamellar thickness of ∼10 nm was formed as a result of the combined effects of the deformation-induced plastic flow, interdiffusion and intermixing of the elements. The crystalline lamellae were related to the multicomponent non-equilibrium solid solution based on the Cu crystal structure. Increase in treatment time to 4 h led to structural changes. The crystalline lamellae underwent refinement that was attributed to dislocation activity and were subdivided into interlamellar blocks. The amorphous lamellae tended to disappear. A body-centered cubic (bcc) Fe solid solution was formed in the layer. Nucleation and growth of bcc Fe precipices in amorphous and crystalline phases were related to increase in Fe content in the layer, which increased with treatment time. The hardness of the as-fabricated layer was almost ten times that of the initial Cu plate.