Study of grain boundary segregation using the Auger electron emission technique. Annual technical progress report VI, January 1, 1976--December 31, 1976. [Summary of research activities at Michigan Tech]

Technical Report · Thu Jan 01 04:00:00 EST 1976

DOI:https://doi.org/10.2172/7313324· OSTI ID:7313324

Stein, D F; Heldt, L A; Lee, J K; Pinchback, T R

Studies of admirality brass stress corrosion in copper sulfate and copper nitrate have provided information on environmental contributions to SCC in acid systems. SCC susceptibility is a function of bulk corrosion rate, and is maximized when conditions favor localized attack. At a given pH and stress, solution composition determines crack initiation rates, but the crack crevice environment is not characteristic of the bulk salt solution. Crack propagation appears to be strongly related to anodic dissolution; however, contributions from thin film rupture and hydrogen embrittlement must be considered. The brittle tarnish rupture mechanism is not operative during the stress corrosion of copper alloys in any of a wide variety of environments. Theoretical models have been developed that are providing a basic understanding of segregation to grain boundaries. The statistical thermodynamic approach using a distribution of energy sites at the grain boundary has extended the McLean model and the results are consistent with sulfur segregation in Ni/sub 3/Al and Ni/sub 3/(Al,Ti). A model based on the interatomic potentials of Cu-Cu, Cu-Bi, and Bi-Bi shows the segregation of Bi should occur at grain boundaries and that the segregation should be more extensive at asymmetrical grain boundaries. This is in agreement with earlier measurements made in this program. Grain boundary diffusion experiments continue. The Mo-S-Cr system is still the most desirable one for this purpose but difficulty has been encountered in controlling the sulfur additions and keeping the Cr plate on the surface. A new closed system has been designed that appears to have solved the problem. Experiments using the Cu-Bi-Ni system have been successful so it is clear that the general approach to studying grain boundary diffusion and the effect of impurity segregation on this diffusion will be successful.

• Research Organization: Michigan Technological Univ., Houghton (USA). Dept. of Metallurgical Engineering
• OSTI ID: 7313324
• Report Number(s): COO-2166-23
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
360205 -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
ALLOYS
AUGER ELECTRON SPECTROSCOPY
BISMUTH
CHEMICAL REACTIONS
COPPER
COPPER ALLOYS
COPPER BASE ALLOYS
COPPER COMPOUNDS
COPPER NITRATES
COPPER SULFATES
CORROSION
CORROSIVE EFFECTS
CRYSTAL STRUCTURE
ELECTRON SPECTROSCOPY
ELEMENTS
GRAIN BOUNDARIES
INTERATOMIC FORCES
METALS
MICROSTRUCTURE
NITRATES
NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
RESEARCH PROGRAMS
SEGREGATION
SPECTROSCOPY
STRESS CORROSION
SULFATES
SULFUR COMPOUNDS
TIN ALLOYS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
ZINC ALLOYS