CRYSTALLOGRAPHIC TEXTURES INDUCED BY DRY SLIDING WEAR IN METALS

Pascal Bellon, University of Illinois at Urbana-Champaign, DMR 0906703

Intellectual Merit

During sliding wear, the severe plastic deformation imposed at contacting surfaces leads to chemical mixing and grain restructuration. The competition between chemical mixing and thermally activated phase separation in multiphase alloys can lead to compositional patterning (see figure). In collaboration with Prof. Averback (University of Illinois) we employed lattice kinetic Monte Carlo simulations to predict the length scale of these patterns and their dependence with deformation temperature and strain rate.

We found that the length scale of these compositional patterns is proportional to the thermal diffusion coefficient and inversely proportional to the strain rate. Simulations have also been used to investigate the effect of strain path, and showed that dominant unidirectional sliding, as found during sliding wear, favors anisotropic, layered nanostructures, as we observed experimentally in Cu-Ag alloys.

Figure: Steady state snapshots of the simulation cell under strain rates (a) 1.0×10 -5 s-1, (b) 1.1×10-7 s-1, (c) 4.9×10-10 s-1, and (d) 3.0×10-11 s-1 at T=400K in a A50B50 alloy with a miscibility gap temperature of 1573 K. The corresponding 2D slices across the cells are shown on the right. Figs. (b-d) illustrate the linear increase in patterning length scale with increasing strain rate. D. Schwen, M. Wang, R. S. Averback, P. Bellon, J. Materials Research, in press (2013).

CRYSTALLOGRAPHIC TEXTURES INDUCED BY DRY SLIDING WEAR IN METALS

Pascal Bellon, University of Illinois at Urbana-Champaign, DMR 0906703

Broader ImpactsIntegrating research and education- A laboratory module on wear of metals has been offered and chosen by 6 senior metals students for their end-of-semester project for the Metals Laboratory course (MSE 442, fall 2012).- The PI organized a field trip for Metals senior students to an Olin brass casting and rolling mill (see photo) to observe alloy processing techniques studied in the classroom, and to discuss alloy development with practicing engineers.

-The PI has served as faculty coordinator for the Departmental Material Advantage (MA) Chapter, and has promoted student participation to technical meetings, including competing at the 2012 MS&T meeting in Pittsburgh, PA. Spencer Wells, the MA president, won the speaking contest.

MatSE undergraduate students visiting the Olin Brass casting and rolling mill facility in East Alton, IL.

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.