Nanocrystallization and α martensite formation in the surface layer of medium-manganese austenitic wear-resistant steel caused by shot peening

The nanocrystallization and alpha martensite formation in the surface layer of medium-manganese austenitic wear-resistant steel subjected to high-energy shot peening treatment were investigated by X-ray diffraction and transmission electron microscopy. The results show that nanograined microstructure, mainly composed of strain-induced alpha martensite grains with the average size of similar to 8 nm were produced in the shot-peened surface. However. any induced phases are not observed in compression-deformed samples with the reduction from 20 to 60%. The examination of grazing-incidence X-ray diffraction in different grazing angles indicates that with decreasing the depth from the shot-peened surface the fraction of strain-induced alpha martensite increases and the grain size decreases. (c) 2007 Elsevier B.V. All rights reserved.