Understanding creep mechanisms of a Cu-Cr-Nb alloy by testing under constant structure conditions

Carbide precipitation and chromium depletion on coherent twin boundaries in deformed 304 stainless steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130717 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1216-1217

Author(s):

A.H. Advani ◽

L.E. Murr ◽

D.J. Matlock ◽

W.W. Fisher ◽

P.M. Tarin ◽

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Keyword(s):

Grain Boundaries ◽

Stainless Steels ◽

Interfacial Free Energy ◽

Carbide Precipitation ◽

Twin Boundaries ◽

Invariant Structure ◽

Heat Treated ◽

Constant Structure ◽

Cr Depletion

Coherent annealing-twin boundaries are constant structure and energy interfaces with an average interfacial free energy of ∼19mJ/m2 versus ∼210 and ∼835mJ/m2 for incoherent twins and “regular” grain boundaries respectively in 304 stainless steels (SS). Due to their low energy, coherent twins form carbides about a factor of 100 slower than grain boundaries, and limited work has also shown differences in Cr-depletion (sensitization) between twin versus grain boundaries. Plastic deformation, may, however, alter the kinetics and thermodynamics of twin-sensitization which is not well understood. The objective of this work was to understand the mechanisms of carbide precipitation and Cr-depletion on coherent twin boundaries in deformed SS. The research is directed toward using this invariant structure and energy interface to understand and model the role of interfacial characteristics on deformation-induced sensitization in SS. Carbides and Cr-depletion were examined on a 20%-strain, 0.051%C-304SS, heat treated to 625°C-4.5h, as described elsewhere.

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Determination of creep mechanisms in various silicon carbides via TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143973 ◽

1986 ◽

Vol 44 ◽

pp. 484-487

Author(s):

C. H. Carter ◽

J. E. Lane ◽

J. Bentley ◽

R. F. Davis

Keyword(s):

Heat Exchangers ◽

Sintered Material ◽

Polycrystalline Material ◽

Chemical Vapor ◽

Graphite Substrate ◽

Second Phase ◽

Reaction Bonding ◽

Creep Mechanisms ◽

Porous Sic

Silicon carbide (SiC) is the generic name for a material which is produced and fabricated by a number of processing routes. One of the three SiC materials investigated at NCSU is Norton Company's NC-430, which is produced by reaction-bonding of Si vapor with a porous SiC host which also contains free C. The Si combines with the free C to form additional SiC and a second phase of free Si. Chemical vapor deposition (CVD) of CH3SiCI3 onto a graphite substrate was employed to produce the second SiC investigated. This process yielded a theoretically dense polycrystalline material with highly oriented grains. The third SiC was a pressureless sintered material (SOHIO Hexoloy) which contains B and excess C as sintering additives. These materials are candidates for applications such as components for gas turbine, adiabatic diesel and sterling engines, recouperators and heat exchangers.

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