CPM Seminar

Computational Materials Design for Aluminum Dry Machining and Quick Plastic Forming

Yue Qi

General Motors R&D
Detroit, Michigan

Demands for light weight and fuel efficient automobiles have led to a steady increase in the use of aluminum alloys for structural components, however the low formability and active surface adhesion of aluminum still raise many challenges in forming and machining of aluminum alloys. In this talk, I will give several examples on how atomic modeling was combined with microstructure modeling and experiments to solve engineering problems and guide material design. First, I'll show a multiscale modeling approach for Quick Plastic Forming of Aluminum. In this model, molecular Dynamics (MD) simulations of grain-boundary sliding (GBS) in aluminum suggested the existence of a threshold stress for GBS. The threshold stress was then included to improve the microstructure plasticity modeling. Finally the simulated stress-strain curves were used to simulate forming of aluminum parts. Consequently, material design can be done at both microstructure and grain boundary level. In solving the aluminum adhesion problem, Density Functional Theory (DFT) was used to directly provide insights and guidance for the coating design on the machining tools. To enable the nano-crystalline diamond coating for aluminum dry machining all three interfaces need to studied: adhesion transfer of Al to the coating surface is minimized; grain boundaries inside the coating is modified to reduce residual stress; and the coating/substrate interface is optimized to enhance the adhesion of the coating. These calculations served as initial steps towards designing new materials and solving engineering problems through multi-scale physics based modeling approach.