The effect of reverted austenite on the mechanical properties and toughness of 12 Ni and 18 Ni (200) maraging steels

Pampillo, C. A.; Paxton, H. W.

doi:10.1007/bf02652858

Cited by 63 publications

(21 citation statements)

References 4 publications

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“…However, there is a limit of increasing toughness by increasing % c because the strength of the material is significantly reduced. It is therefore desirable to limit the % c to below 15% for achieving optimum mechanical properties (Ref [25][26][27].…”

Section: Resultsmentioning

confidence: 99%

“…However, presence of c at prior austenite grain boundaries was not detected. Austenite phase is normally observed in overaged steels formed by diffusion mechanism as a consequence of isothermal treatment above A s temperature ( Ref 7,9,25,31,32). Formation of reverted c is also known to occur by shear mechanism as a result of thermal cycling in the dual a + c phase region ( or as a result of thermal cycling between a fi c (Ref [14][15][16][17][18][19].…”

Section: Discussionmentioning

confidence: 99%

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Effect of Cyclic Aging on Mechanical Properties and Microstructure of Maraging Steel 250

Tariq

Naz

Baloch

2009

J. of Materi Eng and Perform

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The effects of thermal cyclic aging on mechanical properties and microstructure of maraging steel 250 were studied using hardness tester, tensile testing machine, impact tester, optical, scanning electron, and stereo microscopy. Samples were solution annealed at 1093 K for 1 h followed by air cooling to form bcc martensite. Cyclic aging treatments were carried out at 753 and 773 K for varying time periods. Increase in hardness and strength with corresponding decrease in ductility and impact strength was observed with increasing aging cycles. Reverted austenite was detected by x-ray diffraction technique formed as a result of cyclic aging. The presence of reverted c was also confirmed by EDX-SEM analysis and attributed to the formation of Mo-and Ni-rich regions which transformed to c on cooling. Heterogeneity in composition and amount of reverted c was found to increase with increase in aging cycles and aging time. Fractography reveals the change in fracture mode from ductile dimple-like to brittle cleavage with increase in hardness and strength due to cyclic aging.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effect of Cyclic Aging on Mechanical Properties and Microstructure of Maraging Steel 250

Tariq

Naz

Baloch

2009

J. of Materi Eng and Perform

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“…In terms of mechanical properties, Rack and Kalish [19] and Zhu et al [20] found embrittlement in 18Ni (350 ksi grade) maraging steels after low-temperature aging at 673 to 723 K. Overaging decreases strength, ductility, and toughness, [14,19] but there were also reports of improved strength and toughness due to reverted austenite. [20,21] To date, research on Co-free maraging steels has concentrated on T-250 and other grades with 1800 MPa strength level. [2,14,16,[22][23][24][25] Discrepancy among the results exists similar to that for 18Ni Co-containing maraging steels.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and mechanical properties of a 2000 MPa grade co-free maraging steel

Yang

Sha

2005

Metall Mater Trans A

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The precipitation kinetics in the aging temperature range of 713 to 813 K in a 2000 MPa grade Co-free maraging steel (Fe-18.9 pct Ni-4.1 pct Mo-1.9 pct Ti, mass pct) has been studied. Study on microstructure and mechanical properties showed that a great deal of Ni 3 Ti and a type of unknown spheroidal precipitates both with average diameter of 2 to 3 nm are formed in the early aging stage at 713 K, which results in a high strength and a relatively low fracture toughness. Ni 3 Ti precipitates grow into needle or rod shape and become the main precipitation as the aging time is prolonged. Strength increases and fracture toughness (K IC ) decreases with growth of the precipitates. The ultra-high strength of the maraging steel subjected to long-time aging at 713 K is attributed to the high resistance to coarsening of the precipitates. The strengthening in the underaged condition at 713 K is a combination of dislocations cutting through precipitates and the Orowan mechanisms. Aged at 813 K, the size of Ni 3 Ti precipitates is seriously nonuniform at the early stage and a small amount of interlath reverted austenite is formed. Thereafter, Ni 3 Ti precipitates coarsen sharply accompanied with the embrittlement. Intralath reverted austenite appears subsequently. In the later stage of aging, the coarsened Ni 3 Ti precipitates dissolve into the striplike intralath reverted austenite that is disorderly embedded in the matrix. All of these result in a low strength and low fracture toughness under overaging condition. Analysis shows that the formation of reverted austenite contains the diffusion and Kudjumov-Sachs (K-S) and Nishiyama-Wassermann (N-W) shear mechanisms.

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“…Microstructural details accompaning the increased strain hardening for material aged at 968~ for prolonged times have been detailed in Ref. 9. Here, it was shown that the uniform tensile strain rose rapidly from 1 to 2 pct when reverted austenite starts to form (material still in the underaged condition), to about 4 pct at peak yield stress.…”

mentioning

confidence: 84%

Correction to: Structure, strength, and fracture of electrodeposited nickel and Ni−Co alloys

Thompson

Saxton

1974

Metall Trans

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The effect of reverted austenite on the mechanical properties and toughness of 12 Ni and 18 Ni (200) maraging steels

Cited by 63 publications

References 4 publications

Effect of Cyclic Aging on Mechanical Properties and Microstructure of Maraging Steel 250

Effect of Cyclic Aging on Mechanical Properties and Microstructure of Maraging Steel 250

Microstructure and mechanical properties of a 2000 MPa grade co-free maraging steel

Correction to: Structure, strength, and fracture of electrodeposited nickel and Ni−Co alloys

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