Microstructure and Properties of Zr-4 Alloy after Surface Mechanical Attrition Treatment

Surface nanocrystallization of Zr-4 alloy was conducted by means of surface mechanical attrition treatment (SMAT). The surface layers of samples processed SMAT for different times were characterized by means of X-ray diffraction,optical microscope and roughness instrument. Microhardness tester was applied to identify the hardness of the sample at different depths. The results show that SMAT didnt change the XRD patterns of the sample. The average grain size of Zr-4 alloy surface was refined to the minimum value of 20 nm after SMAT for 15 min. A certain thickness of plastic deformation layer formed on the surface after SMAT. After SMAT for 60 min,the surface hardness of the alloy was about 1.3 times of the base hardness and decreased with the increase of the depth from the surface. Roughness of the alloy increased first and then declined to a stable value with the increase of SMAT time.