Role of surfaces and interfaces in controlling the mechanical properties of metallic alloys.
This article explores the subtle effects of surfaces and interfaces on the mechanical properties of bulk metallic alloys using three examples: environmental effects on fatigue life, hydrogen embrittlement effects on the ductility of intermetallics, and the role of coherent precipitates in the toughness of steels. It is demonstrated that the marked degradation of the fatigue life of metals is due to the strong chemisorption of adsorbates on exposed slip steps that are formed during fatigue deformation. These adsorbates reduce the reversibility of slip, thus accelerating fatigue damage in a chemically active gas environment. For certain intermetallic alloys such as Ni(3)Al and Ni(3)Fe, the ductility depends on the ambient gas composition and the atomic ordering in these alloys, both of which govern the complex surface chemical reactions taking place in the vicinity of crack tips. Finally, it is shown that local stresses at a coherent precipitate-matrix interface can activate dislocation motion at low temperatures, thus improving the fracture toughness of bulk alloys such as steels at cryogenic temperatures. These examples illustrate the complex interplay between surface chemistry and mechanics, often yielding unexpected results.
Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Taejon 305-701, South Korea.
Won-Jong
WJ
Lee
Wen-Jui
WJ
Chia
Jinliu
J
Wang
Yanfeng
Y
Chen
Semyon
S
Vaynman
Morris E
ME
Fine
Yip-Wah
YW
Chung
D000327:Adsorption; D000497:Alloys / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry*; D001895:Boron / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D000497:Alloys; D014867:Water; D009532:Nickel; D006859:Hydrogen; D000535:Aluminum; D007501:Iron; D001895:Boron; D010100:Oxygen