Research Projects

DISCONTINUOUSLY REINFORCED NANO-ALUMINUM COMPOSITES

Faculty Mentors: Profs. L. Ann , Q. Chen and S. Seal

Research Description

Discontinuously reinforced aluminum composites are emerging engineering materials due to their potential applications in aircraft engines, automobile brakes and substrates for electrical packaging. These applications require a variety of mechanical properties in the composites, such as high elastic modulus, high yield strength, reasonable ductility, high creep resistance at high temperature and tailored thermal conductivity. For example, the yield strength and creep resistance are determined by the pinning of dislocations, the spacing between the "pinning point" must be less than 100 nm to obtain significant strengthening. Most recently, the composites, consisting of aluminum and 10vol% spinel particles, were prepared by powder metallurgical methods and showed very unusual properties when the size of spinel particles is < 100 nm. For example, the thermal and electrical conductivities dropped 4 times, way out of limitations predicted by any existing models. The creep rate and stress exponent are also dramatically changed. The studies indicated the solid-state based ion exchange between aluminum and Mg in spinel, which counts qualitatively for thermal/electrical conductivities. While the mechanism underlying the unique mechanical behavior is remain unknown. Also understanding nanoscale tribology (friction, wear and lubrication) is very important for both understanding nanosciences and developing these nanoscale systems.

The undergraduates will be involved in:

• Learning mechanical alloying and sol-gel methods to make composites with 5 and 10 vol% of spinel phase of
• Understand the effect of particle sizes on microstructures using SEM (microstructure), TEM (dislocation structure), XRD (phase) and XPS (chemistry) and subsequent learning of handling these instruments.
• Acquainted with the nanoindentation technique to measure mechanical properties such as elastic modulus, and yield strength.
• Hands on training with AFM and LFM (Lateral Force Microscopy) to measure tribological properties in nanoscale.