Deformation effects on transgranular carbide precipitation in 304 stainless steels

1992 ◽  
Vol 50 (1) ◽  
pp. 260-261
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D.J. Matlock ◽  
W.W. Fisher ◽  
P.M. Tarin ◽  
...  
Keyword(s):  
Stainless Steels ◽  
True Strain ◽  
Carbide Precipitation ◽  
Material Research ◽  
Chromium Depletion ◽  
Engineering Strain ◽  
Twin Fault ◽  
Heat Treated ◽  
Strain Induced Martensite ◽  
The Relationship

Plastic deformation is a key variable producing accelerated intergranular (IG) carbide precipitation and chromium-depletion (sensitization) development in stainless steels. Deformation above 20% also produces transgranular (TG) carbides and depletion in the material. Research on TG carbides in SS is, however, limited and has indicated that the precipitation is site-specific preferring twin-fault intersections in 316 SS versus deformation-induced martensite and martensite lath-boundaries in 304 SS. Evidences indicating the relation between martensite and carbides were, however, sketchy.The objective of this work was to fundamentally understand the relationship between TG carbides and strain-induced martensite in 304 SS. Since strain-induced martensite forms at twin-fault intersections in 304 SS and the crystallography of the transformation is well understood, we believed that it could be key in understanding mechanisms of carbides and sensitization in SS. A 0.051% C, 304 SS deformed to ∽33% engineering strain (40% true strain) and heat treated at 670°C/ 0.1-10h was used for the research. The study was carried out on a Hitachi H-8000 STEM at 200 kV.

EM study of carbon content effects on carbide precipitation and chromium depletion in type 304 stainless steels

1993 ◽  
Vol 51 ◽  
pp. 1164-1165
Author(s):  
E.A. Trillo ◽  
A.H. Advani ◽  
L.E. Murr ◽  
W.W. Fisher
Keyword(s):  
Carbon Content ◽  
Stainless Steels ◽  
Test Methods ◽  
Carbide Precipitation ◽  
Valuable Insight ◽  
Chromium Depletion ◽  
Electrochemical Test ◽  
Heat Treated ◽  
Precipitation Characteristics ◽  
Type 304

Carbon content is the most critical compositional variable in carbide precipitation and sensitization development in stainless steels (SS). Quantitative electrochemical test methods have conclusively demonstrated that an increase in carbon content enhances the susceptibility of SS to sensitization development. The increase in sensitization has been considered to be caused by the influence of carbon on the thermodynamics of the precipitation-depletion process. This has been supported by limited TEM work. In this research, we are using electron microscopy to quantify the effects of carbon content on carbide precipitation and chromium-depletion development in SS. Initial observations that compare precipitation characteristics and depletion profiles in 0.011% C, 0.025% C, 0.051% C, and 0.07% C-containing, 304 SS heat treated at 775°C for 0.1-500 h are presented in this paper, and will be enhanced by a statistical analysis of carbon content effects on precipitate sizes, densities, and depletion profiles, to provide a valuable insight into the precipitation-depletion phenomena.

Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

1991 ◽  
Vol 49 ◽  
pp. 604-605
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D. Matlock
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Deformation Twin ◽  
Austenitic Stainless Steels ◽  
Carbide Precipitation ◽  
Strain Induced Martensite ◽  
Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

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

1992 ◽  
Vol 50 (2) ◽  
pp. 1216-1217
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D.J. Matlock ◽  
W.W. Fisher ◽  
P.M. Tarin ◽  
...  
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.

Deformation Effects on Intragranular Carbide Precipitation and Transgranular Chromium Depletion in Type 316 Stainless Steels

CORROSION ◽  
1991 ◽  
Vol 47 (12) ◽  
pp. 939-947 ◽  
Author(s):  
A. H. Advani ◽  
L. E. Murr ◽  
D. G. Atteridge ◽  
R. Chelakara ◽  
S. M. Bruemmer
Keyword(s):  
Stainless Steels ◽  
Carbide Precipitation ◽  
Chromium Depletion ◽  
Intragranular Carbide

Mechanisms of transgranular carbide precipitation in deformed 304 stainless steels

1993 ◽  
Vol 51 ◽  
pp. 1168-1169
Author(s):  
A. H. Advani ◽  
L.E. Murr ◽  
W.W. Fisher
Keyword(s):  
Recent Work ◽  
Stainless Steels ◽  
High Strain ◽  
Lath Martensite ◽  
Austenitic Stainless Steels ◽  
Carbide Precipitation ◽  
Carbide Formation ◽  
Lattice Image ◽  
Site Specific ◽  
Heat Treated

Transgranular (TG) carbides form in thermomechanically processed austenitic stainless steels (SS) when the material is plastically deformed to high strain levels, typically above 20%, and for heat treatments that lie within the 500-850°C sensitization range of the SS. In recent work, we have shown that the TG carbide precipitation is site-specific, and favors deformation-induced sites created during the straining process. Specifically, twin-faults and their intersections, and dislocation intersections have been indicated to be preferred sites forTG carbide formation in 304 and316 SS, while clustered regions containing a mix of fine-austenite and lath martensite were also observed to be critical sites for the TG precipitation in 304 SS. In this paper, we present lattice image observations of carbide precipitates in the TG fme-austenite/lath martensite regions of 40% deformed, 670°C/0.1-10h heat treated, 0.051%C 304 SS, as a means to understand the mechanisms of TG carbide precipitation in the SS.

A TEM study of the effect of oxygen on nanocavity formation and precipitation in rapid - solidified Fe-16Ni-9Cr stainless steels

1994 ◽  
Vol 52 ◽  
pp. 700-701
Author(s):  
S. Wisutmethangoon ◽  
T. F. Kelly ◽  
J.E. Flinn
Keyword(s):  
Stainless Steels ◽  
High Mobility ◽  
Hot Extrusion ◽  
Extrusion Ratio ◽  
Gas Atomization ◽  
Cavity Formation ◽  
Nucleation Sites ◽  
Heat Treated ◽  
Different Types ◽  
Effect Of Oxygen

Vacancies are introduced into the crystal phase during quenching of rapid solidified materials. Cavity formation occurs because of the coalescence of the vacancies into a cluster. However, because of the high mobility of vacancies at high temperature, most of them will diffuse back into the liquid phase, and some will be lost to defects such as dislocations. Oxygen is known to stabilize cavities by decreasing the surface energy through a chemisorption process. These stabilized cavities, furthermore, act as effective nucleation sites for precipitates to form during aging. Four different types of powders with different oxygen contents were prepared by gas atomization processing. The atomized powders were then consolidated by hot extrusion at 900 °C with an extrusion ratio 10,5:1. After consolidation, specimens were heat treated at 1000 °C for 1 hr followed by water quenching. Finally, the specimens were aged at 600 °C for about 800 hrs. TEM samples were prepared from the gripends of tensile specimens of both unaged and aged alloys.

Structural Defects and Changes in Al-Pd-Fe Crystalline Approximant

2007 ◽  
Vol 26-28 ◽  
pp. 687-690 ◽  
Author(s):  
J.P. Wang ◽  
Wei Sun ◽  
Z. Zhang
Keyword(s):  
Heat Treatment ◽  
High Resolution Electron Microscopy ◽  
Structural Defects ◽  
Decagonal Quasicrystal ◽  
High Temperature Heat Treatment ◽  
Atom Clusters ◽  
Heat Treated ◽  
Resolution Electron ◽  
The Relationship ◽  
Temperature Heat Treatment

Crystalline approximants structurally related to decagonal quasicrystal in the as-cast and heat-treated Al75Pd15Fe10 alloys and defect structures in them have been studied by means of high-resolution electron microscopy (HREM). Structural defects of linear and planar types were found to exist extensively in the orthorhombic ε16-phase formed in the as-cast Al75Pd15Fe10 alloy. In contrast with the distribution and configuration of the defects in the as-cast ε16-phase, we found that high-temperature heat treatment promotes the formation of a kind of regular network of structural defects in the ε16-phase. This suggests that rearrangements of atom clusters and as well as defects occurred due to the heat treatment. The relationship between the distribution of atom clusters and the configuration of defects will be discussed.

Effects of High Magnetic Fields on Martensitic Transformation at Cryogenic Temperatures for Variously Heat Treated Stainless Steels

1994 ◽  
pp. 1207-1213 ◽  
Author(s):  
Koji Shibata ◽  
Yasushi Kurita ◽  
Tsutomu Shimonosono ◽  
Yoshiaki Murakami ◽  
Satoshi Awaji ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Magnetic Fields ◽  
Stainless Steels ◽  
High Magnetic Fields ◽  
Cryogenic Temperatures ◽  
Heat Treated
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