Walter P. Murphy Professor Emerita

BS, physics, 1946

MS, physics, 1947

DSc, physics, 1951 Carnegie Institute of Technology (now Carnegie Mellon University)

Contact Info

Mechanical behavior of advanced materials

As the dimensions of the grains in a metal drop below ~10-20 nanometers, the number of atoms located at interfaces and grain boundaries becomes an appreciable fraction of the total.  Deformation mechanisms operating in this class of materials are fundamentally different from those in the coarse-grain counterparts. Nanostructured materials are amazingly strong but present challenges in synthesis and especially in devising internal structures that provide sufficient toughness.  We continue to explore new synthesis methods and advanced characterization techniques to understand how dislocations and grain boundary sliding mechanisms operate at this small size scale where conventional theory breaks down, with the goal of learning how to improve the properties of these materials.  A current thrust is the determination of the mechanical behavior of nanocrystalline materials and their structural stability under cyclic deformation (i.e., fatigue), an important and typically far more damaging form of service wear.  We are also looking at their microstructural stability under stress. Nanocrystalline grains can undergo rapid growth under stress at room temperature, but counter-intuitively, we found that the growth is even faster at liquid nitrogen temperatures.  Recently we have concentrated on characterizing the behavior of nanotwinned metals under various types of deformation.  This promising nanostructure is about as strong and far more stable than equivalent 3D nanocrystalline material.

Associations and Awards

Member, National Academy of Engineering, 1988
NSF awards for creativity in research, 1981 and 1986
Guggenheim Fellowship, 1986-87
Fellow, ASM International, 1988; TMS, 1992; American Academy of Arts and Science, 1997
Member, National Research Council's National Materials Advisory Board, 1999-2005
Distinguished Engineering Educator Award of SWE, 1989
SWE's highest honor, the Achievement Award, 1991
Leadership Award, TMS, 1996
Materials Research Society's highest honor, the Von Hipple Award, 2003
Gold Medal of ASM International, 2005
Institute of Metals/Robert Mehl Lecture, TMS, 2006
Fellow, Neutron Scattering Society of America, 2007
Honorary Member ASM, 2011

Publications

"Rapid Stress-Driven Grain Coarsening in Nanocrystalline Cu at Ambient and Cryogenic Temperatures", with K. Zhang and J.A. Eastman, Applied Physics Letters 87 (2005) 061921.

"Pore Distributions in Nanocrystalline Metals from Small-Angle Neutron Scattering", with P.G. Sanders and J.A. Eastman, Acta Materialia, 46 (1998) 4195-4202.

"In-situ TEM Tensile Testing of DC Magnetron Sputtered and Pulsed Laser Deposited Ni Thin Films", R.C. Hugo, H. Kung, J.R. Weertman, R. Mitra, J.A. Knapp and D.M. Follstaedt, Acta Materialia 51 (2003) 1937-43.

“Mechanical Behavior of Nanocrystalline Metals”, in Nanostructured Materials:  Processing, Properties and Applications, 2nd edition, C.C. Koch, Ed., William Andrews, Pub. 537-561.

“Detwinning, Damage and Crack Initiation during Cyclic Loading of Cu Samples Containing Aligned    Nanotwins”, C.J. Shute, B.D. Myers, S. Xie, S.-Y. Li, T.W. Barbee, Jr., A.M. Hodge, J.R. Weertman, Acta Materialia, 59 (2011) 4569-4577.

“High-pressure torsion of copper samples containing columns of highly aligned nanotwins”,
C.J. Shute, B.D. Myers, Y. Liao, S.-Y. Li, A.M/ Hodge, T.W. Barbee, Jr., Y.T. Zhu and
J.R.Weertman, Scripta Materialia 65 (2011) 899-902.