Study the Wear and Corrosion Resistances of Ultra-Strong /Plastic Mg-Based Supra-Nano-Dual-Phase Materials

Description

The ultrastrong and ultrahard alloy with theoretical strength is always a hot research topic, due to its promising application potential in industry. However, the theoretical strength (E/20, where E is the elastic modulus) is not able to achieve in the macroscopic material currently, which remarkably restricts the engineering application of theoretically strong materials. The single phase nanocrystalline alloys and single phase metallic glasses have very high strength. However, they are usually softened at <2% strain with an ultimate stress around E/85~E/50 because of the reverse Hall–Petch effect and the softening effect of shear band, respectively. In brief, known mechanisms for strengthening crystalline materials could hardly reach the theoretical strength to E/20.We recently developed an ultra-high strength material – Mg-based supra-nano-dualphase glass-crystal (SDNP-GC), which has an in-situ formed amorphous-nanocrystalline nanostructure, exhibits theoretical strength of 3.3 GPa without sample size effect at room temperature. This strength is 10 times higher than that of the ever-reported strongest Mg alloy and 6 times higher than commercial steel. Preliminary TEM analysis, constitutive modeling and molecular dynamics (MD) simulations suggested that this ultra-high strength owed to strain delocalization by multiple embryonic shear bands and strain hardening of nanocrystals.In addition, we recently discovered this ultra-strong SNDP-GC nanostructure would have plasticity and self-lubrication behaviors under certain conditions. Further investigations on the formation mechanisms of these two aspects would definitely have profound implications for designing materials with unprecedented mechanical properties. The outcome will pave a novel and effective way to generate SNDP-GC metals (such as Mg alloys) with good ductility and ultrahigh wear resistance. Our endeavors would facilitate industrial applications in high strength MEMS devices11, surface coatings with high wear resistance and 3D printed microstructures, benefits to fundamental research on materials engineering and the whole society.To improve understanding of the mechanisms for the formation of SNDP-GC nanostructures and its role in the significant enhancement of mechanical properties, the proposed research will be composed of 5 tasks: (1) Study the microstructure evolution of Mgbased SNDP-GC produced by physical vapor deposition with different deposition parameters and comparatively study the mechanical behaviors of SNDP-GC; (2) Study the selflubrication behavior of SNDP-GC under wear and wear property improvement of Mg alloy by depositing the SNDP-GC; (3) Study the plasticity generation mechanism of multilayered SNDP-GC/metallic glass (MG) films; (4) Investigate the corrosion mechanism of SNDP-GC; (5) Comparison between experimental results and MD simulation.