| The Stability of Precipitated Austenite and the Toughness of 9Ni Steel, |
DEC 1985 |
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| Authors:
B. Fultz; J. I. Kim; Y. H. Kim; H. J. Kim; G. O. Fior
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 | A correlation was confirmed between the good low temperature Charpy toughness of 9Ni steel and the stability of its precipitated austenite against the martensitic transformation. Changes in the microstructure during isothermal tempering were studied in detail. The austenite/martensite interface is originally quite coherent over about 100 A distances. With further tempering, however, the dislocation structure at the austenite/martensite interface changes, and this change may be related to the increased instability ... |
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| The Role of the Constituent Phases in Determining the Low Temperature Toughness of 5.5Ni Cryogenic Steel |
DEC 84 |
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| Authors:
J. I. Kim; H. J. Kim; J. W. Morris Jr.
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| Ferritic Fe-Ni steels that are intended for service at low temperature are usually given an intercritical temper as the final step in their heat treatment. The temper dramatically decreases the ductile-brittle transition temperature, T(sub B). Its metallurgical effect is to temper the lath martensite matrix and precipitate a distribution of fine austenite particles along the lath boundaries. Prior research suggests that the low value of T(sub B) is a consequence ... |
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| A Metallographic Interpretation of the QLT Heat Treatment of Ferritic Cryogenic Steels |
MAY 1982 |
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| Authors:
J. I. Kim; J. W. Morris Jr; CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND MINERAL ENGINEERING
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| Commercial 5-6Ni steels are toughened for service by a 3-step heat treatment which is sometimes designated the QLT treatment. The present investigation was undertaken to determine why this treatment is necessary and successful. It was concluded that the multi-step heat treatment is necessary because of the low nickel content. The intercritical anneal (L) serves to create regions of high solute contents along the martensite lath boundaries. The intercritical temper (T) ... |
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| Microstructural Sources of Toughness in QLT-Treated 5.5 Ni Cryogenic Steel |
SEP 1981 |
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| Authors:
J. I. Kim; C. K. Syn; J. W. Morris Jr; CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| In commercial practice 5.5Ni steel is toughned for cryogenic service by a three-step heat treatment designated the 'QLT' treatment. To determine why this treatment is necessary and successful, a series of two-step heat treatments were applied to 5.5.Ni steel and the resulting microstructural states were characterized and compared with that resulting from the QLT treatment. It was concluded from this analysis that the QLT treatment lowers the ductile-brittle transition essentially ... |
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| The Composition of Precipitated Austenite in 5.5 Ni Steel |
OCT 1980 |
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| Authors:
J. I. Kim; J. W. Morris Jr; CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND MINERAL ENGINEERING
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| Both Scanning Transmission electron microscopic (STEM) and chemical extraction techniques were used to analyze the chemical content of precipitated austenite in 5.5 Ni steel as a function of heat treatment. Austenite was introduced into the steel by tempering at 600 degrees C for 2 hours (OT) or 100 hours (OT100), by tempering for 1 hour at 670 degrees C (OL), or by double tempering 1 hour at 670 degrees C ... |
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| On the Scavenging Effect of Precipitated Austenite in a Low Carbon Fe-5. 5Ni Alloy |
AUG 80 |
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| Authors:
J. I. Kim; J. W. Morris Jr.
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| The scavenging effect of precipitated austenite in a low carbon, commercial Fe-5.5Ni cryogenic alloy was investigated through observation of the dissolution of cementite precipitates during intercritical tempering and study of the associated change in Charpy impact toughness. Cementite precipitates initially located along prior austenite grain boundaries were gradually dissolved into reverted austenite as the intercritical tempering proceeded. The austenite tends to form at or around the carbide particles and may ... |
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| Advances in the Heat Treatment of Steels. |
JUL 1979 |
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| Authors:
J. W. Morris Jr.; J. I. Kim; C. K. Syn; CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| A number of important recent advances in the processing of steels have resulted from the sophisticated uses of heat treatment to tailor the microstructure of the steels so that desirable properties are established. These new heat treatments often involve the tempering or annealing of the steel to accomplish a partial or complete reversion from martensite to austenite. The influence of these reversion heat treatments on the product microstructure and its ... |
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| Consequences of the Re-Transformation of Precipitated Austenite in Ferritic Cryogenic Steels |
JUN 79 |
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| Authors:
J. W. Morris Jr.; C. K. Syn; J. I. Kim; B. Fultz; CALIFORNIA UNIV BERKELEY LAWRENCE BERKELEY LAB
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| The re-transformation of precipitated austenite in Fe(6-9)%Ni steels has been investigated, with particular emphasis on the influence of transformation characteristics on alloy toughness at cryogenic temperature. In all cases studied the precipitated austenite re-transforms, either during cooling to cryogenic temperature or during deformation prior to fracture of the alloy. When the re-transformation is thermally induced the product martensite tends to form in a variant identical to that present before precipitation ... |
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