Microstructural evolution of Ni sheets under single ball collisions

• Published in: Journal of alloys and compounds 2012-09, Vol.536 (SUPPL.1), p.S21-S25
• Main Authors: Romankov, S., Hayasaka, Y., Kang, H.J., Shchetinin, I.V., Yoon, J.M.
• Format: Article
• Language: English
• Subjects: Ball impacts; Collisions; Evolution; Grain refinement; Grain size; Microstructure; Nanostructured materials; Nickel; Severe plastic deformation; Surface layer; Texture; Texture development; Vibration
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2011.12.004

► The Ni sheets were treated by single ball impacts in the vibration mill. ► The Ni rolling texture was destroyed after 5-min treatment. ► The smaller balls were more effective for grain refinement. ► 20-nm grain size may be attained after 30-min treatment. ► Hardness increased more than five times after 30-min treatment. The Ni sheets were treated by single ball impacts in the vibration mill. The microstructural evolution and formation of the nanocrystalline grains were investigated as a function of the processing time and the ball size. The smaller balls were more effective for grain refinement. After 15-min treatment, the grain size was around 300nm for 20-mm ball and 70nm for 15-mm balls. 20-nm grain size may be attained after 30-min treatment by 20-mm ball. The difference in microstructural evolution was attributed to the impact frequency that appeared to be higher for the smaller balls at a present experimental condition. Ball collisions destroyed the initial rolling texture and could lead to the formation of the fiber texture. After 30-min treatment by 20-mm ball, microhardness increased more than five times.