Professor of the Graduate School of Materials Science and Engineering


484 Hearst Memorial Mining Building

Berkeley,  CA 94720-1760



Phone: (510) 642-3815

Research Website:


Gum Metal and the Limits of Strength
    This project is based on a set of titanium alloys known as "gum metal"  that exhibit unique deformation characteristics after cold-working.  In the annealed condition, deformation is accompanied by dislocation motion and giant faults. However, typical deformation mechanisms such as twinning and dislocations have not been reported for the cold-worked material and it appears to deform at the ideal strength in this condition.  To investigate the difference in behavior between the conditions, we are using a combination of in situ techniques with high resolution electron microscopy.
Lead-Free Solder for Microelectronics

    In this project, we investigate the reliability, microstructure and mechanical properties of environmentally friendly Pb-free solders.  Current research uses a custom built apparatus for mechanical testing of solder joints under current, at elevated temperatures, or a combination of conditions. A wide array of sample types are tested, from idealized simple shear specimens to complete microelectronic packages, to better understand the complex interactions that occur in these interconnects.
Other, past research in this area has included solder substrate reactions and wetting characteristics, microstructure forms and stability, and methods of accelerated testing to ensure reliability in service.  Future projects building on this body of research are under development.

Mechanisms of Grain Refinement in High Strength Steels
    In this project, we investigated the role and control of coherent tansformations in achieving ultrafine size in high strength steel. The project produced new characterization techniques for identifying coherent transformations, new understanding of the role of coherent transformations in nominally diffusional processes, and new methods to produce exceptional properties.  While no current research is underway in this area, steel is a commercially  critical material, thus there is always research potential in this and related areas.