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Charles J. McMahon, Jr. Professor 400 LRSM 215.898.7979 cmcmahon@lrsm.upenn.edudownload CV |
B.S. Metallurgical Engineering, University of Pennsylvania, 1955.
Sc. D., Physical Metallurgy, Massachusetts Institute of Technology, 1963.
Research Interests
Physical metallurgy, micromechanisms of deformation and fracture, surface and interface phenomena.
Current Research Projects:
Dynamic Embrittlement
High-strength materials can undergo failure by decohesion, usually along grain boundaries, if a high tensile stress is applied while a surface-adsorbed low-melting-point element is present on the surface at a temperature where the surface element is mobile. A theory has been developed to model the diffusion-controlled crack-growth, and it is being tested with a variety of materials, both polycrystals and bicrystals, including alloy steels, copper-based and nickel-based alloys, and an iron-silicon alloy. The surface elements originate from either a vapor or a surface coating (solid or liquid) or from solid solution in the alloy being studied. This phenomenon is actually widespread in engineering materials, but the mechanism is not widely appreciated.
Selected Publications
- "The Effect of Boron on Stress-Relief Cracking of Alloy Steels," S. Ishikawa, J. A. Pfaendtner, and C. J. McMahon, Jr., Matls. Sci. Eng., A272 (1999) 16-23
- "Oxygen-Induced Intergranular Cracking of a Ni-base Alloy at Elevated Temperatures - An Example of Dynamic Embrittlement," J. A. Pfaendtner and C. J. McMahon, Jr., submitted to Acta Mater.
- "Hydrogen-Induced Intergranular Fracture in Steels," Eng. Fracture Mech., in press.
- "Thermodynamics and Kinetics of Interfacial Decohesion," Y. Mishin, C. J. McMahon, Jr., J. L. Bassani, and P. Sofronis, MRS Symposium, Fall Meeting, 1999, in press.