CRYSTALLOGRAPHIC TEXTURES INDUCED BY DRY SLIDING WEAR IN METALS Pascal Bellon, University of Illinois at Illinois at Urbana-Champaign, DMR Intellectual Merit During sliding wear, the severe plastic deformation imposed at contacting surfaces leads to chemical mixing and grain restructuration. We discovered a novel nanoscale self- organization reaction triggered by these processes in Cu-Ag two- phase alloys. Cu 90 Ag 10 alloys with initial microstructures comprised of equiaxed Ag precipitate with tunable sizes have been obtained by ball-milling, warm pressing, and heat treatment through a collaboration with Profs. Averback and Dillon. After sliding wear, just below the wear surface, the microstructure has spontaneously evolved into alternating nanolayers of Cu and Ag. The thickness of the layers decreases upon approaching the wear surface, as the imposed shear strain increases. This novel nanolayering reaction leads to a reduction of the friction coefficient and of the wear rate, as Ag acts as a solid lubricant. This finding opens a novel route for the design of materials that can spontaneously adapt and resist to aggressive wear environments. Figure: Z-contrast scanning transmission electron microscopy imaging: (top) initial equiaxed Cu 90 Ag 10 alloy (Ag precipitates appear brighter due to their higher atomic number); (bottom) self-organized nanolayers just below the wear surface after sliding wear test at RT, 10 N load, and 0.25 m/s sliding velocity. The scale bar holds for both micrographs. Sliding direction Initial two-phase Cu 90 Ag 10 Spontaneous nanolayering induced by wear

CRYSTALLOGRAPHIC TEXTURES INDUCED BY DRY SLIDING WEAR IN METALS Pascal Bellon, University of Illinois at Illinois at Urbana-Champaign, DMR Broader Impacts Integrating research and education - One REU student, Aaron Dahlke has contributed to the research on sliding wear of bronze, Cu-Ag, and Cu-Nb multilayers. These results will be presented at the 2013 TMS Annual meeting. - A laboratory module on wear of metals has been added to the senior Metals Laboratory course (MSE 442), and coordinated by Aaron Dahlke. - Nanostructuring by Severe Plastic Deformation have been integrated into a course on “Materials for Nanotechnology” (MSE 487) taught by the PI in spring 2011 and spring Promoting collaborations and science - An international collaboration is pursued with Prof. H. Hahn (Karlsruhe Institute of Technology) to compare microstructures developed in Cu-Ag and Cu-Nb under high pressure torsion testing and sliding wear testing. - The PI collaborates with Drs. I. Beyerlein and N. Mara (LANL) to investigate the wear resistance of Cu-Nb nanolayered material in relationship with their initial texture and microstructure. MatSE undergraduate students from UIUC at the MS&T 2011 meeting in Columbus, OH. Parul Kaul (3rd from right) won the speaking contest. -The PI has served as faculty coordinator for the Departmental Material Advantage Chapter, and has promoted student participation to technical meetings, including competing at the 2011 MS&T meeting in Columbus, OH.