Abstract: A nanostructured surface layer was synthesized on a low carbon steel by using surface mechanical attrition (SMA) technique. The refined microstructure of the surface layer was characterized by means of different techniques, and the hardness variation along the depth was examined. Experimental results show that the microstructure is inhomogeneous along the depth. In the region from top surface to about 40 mm deep, the grain size increases from about 10 nm to 100 nm. In the adjacent region of about 40-80μm depth, the grain size increases from about 100nm to 1000 nm. The grain refinement can be associated with the activity of dislocations. After the SMA treatment, the hardness of the surface layer is enhanced significantly compared with that of the original sample, which can primarily be attributed to the grain refinement.

Key words: Low carbon steel, Surface mechanical attrition, Surface nanocrystallization...