Nanocrystalline alloys: Impervious to Fatigue Failure?
Event details
| Date | 17.09.2014 |
| Hour | 11:00 › 12:00 |
| Speaker |
Dr. Brad Boyce, Sandia National Laboratories in Albuquerque, New Mexico, USA Bio : Dr. Boyce is a Distinguished Member of the Technical Staff at Sandia National Laboratories in Albuquerque, New Mexico, USA. Dr. Boyce received the B.S. degree from Michigan Technological University in 1996 in Metallurgical Engineering and the M.S. and Ph.D. degrees in 1998 and 2001 from the University of California at Berkeley in Materials Science and Engineering. Dr. Boyce joined the technical staff at Sandia in 2001 where his research interests lie in micromechanisms of deformation and failure. He was promoted to Principal Staff in 2005, and received the special appointment of Distinguished Staff in 2014. He has over 70 peer reviewed archival publications (H-index=23) in areas such as microsystems reliability, nanoindentation, fracture in structural alloys, weld metallurgy, ocular tissue viscoelasticity, and fatigue mechanisms. Dr. Boyce has served as a Key Reader for Metallurgical and Materials Transactions, and has served as a guest editor for Thin Solid Films, Experimental Mechanics, International Journal of Fatigue, and International Journal of Fracture as well as several MRS proceedings books. He has organized 10 technical symposia at international conferences and has chaired the Rio Grande Symposium on Advanced Materials. Dr. Boyce is a past recipient of the Hertz Foundation fellowship, TMS Young Leader award, and ASM’s Marcus A. Grossman Young Author award. Dr. Boyce leads several large-team research programs at Sandia, totaling over $4M in annual funding. |
| Location | |
| Category | Conferences - Seminars |
Abstract : Fatigue failure is the process by which materials break during repetitive loading. These failures cost the US economy several billion dollars each year. In metals and alloys, fatigue cracks nucleate by an atomic-scale process called ‘persistent slip’. Transmission electron microscopy studies of conventional coarse grained metals show persistent slip bands as dislocation ladder structures with dimensions of several 100’s of nanometers to micrometers. However, in nanocrystalline alloys the grain size itself is less than 100 nanometers, thereby suppressing the formation of a persistent slip structure. We have examined this phenomenon in three nanocrystalline nickel based alloys and compared behavior to their annealed coarse grained counterparts. In all three nanocrystalline nickel alloys, failure is preceded by fatigue-driven grain growth. Only when the grains are grown mechanically to several 100’s of nanometers, does crack nucleation occur. These nanocrystalline alloys demonstrate substantial enhancement in fatigue resistance compared to conventional structural metals, even when scaled by the Hall-Petch strength enhancement.
Practical information
- General public
- Free
Organizer
- IGM-GE
Contact
- Géraldine Palaj