Process of Surface Nanocrystallization of Age-Hardening Cu-2Ti Alloy

The process of SMAT (surface mechanical attrition treatment) of Cu-2Ti alloy (mass fraction, similarly hereinafter) was studied. The microstructure analysis were conducted both on solid solution alloy and on aged alloy. The results showed that obvious stratified phenomenon appeared on the surface of the sample after different treatment. A homogeneous nanostructured surface layer was formed on the Cu-2Ti alloy and the thickness varied according to the SMAT time. There is a clear interface between the nanostructured layer and the coarse-grain layer. The transition zone from fine grain to coarse didn't form, but high density of deformation twins appeared, which may be due to the grain refinement that changes the deformation mechanism from twin to dislocation glide. The hardness of the stratified interface of the sample, which was suffered solid solution+SMAT+aging, is increased sharply. This may result from the combined action of precipitation strength ening, twin strength ening and fine grained strength ening.