Steady state creep behaviour of NiAl hardened austenitic steel

Satyanarayana, D.V.V.; Malakondaiah, G.; Sarma, D. S.

doi:10.1016/s0921-5093(01)01342-9

Cited by 66 publications

(36 citation statements)

References 28 publications

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“…Thus, it was the B2 phase with approximately 10 vol pct that was identified as increasing the creep resistance, rather than the relatively lower number of nanoscale MC particles. Satyanarayana et al [26,27] have systematically investigated the strengthening mechanism of the B2 phase precipitate in Fe-14Cr-21Ni-4.5Al (wt pct) base austenitic alloy at elevated temperatures, which revealed the benefits of the B2 phase precipitate strengthening up to approximately 400°C. This indicates that the evaluation temperature in the present work was too high for the B2 phase strengthening to be the primary source of creep resistance.…”

Section: Discussionmentioning

confidence: 99%

Effect of Alloying Additions on Phase Equilibria and Creep Resistance of Alumina-Forming Austenitic Stainless Steels

Yamamoto

Santella

Brady

et al. 2009

Metall Mater Trans A

102

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The high-temperature creep properties of a series of alumina-forming austenitic (AFA) stainless steels based on Fe-20Ni-(12-14)Cr-(2.5-4)Al-(0.2-3.3)Nb-0.1C (weight percent) were studied. Computational thermodynamics were used to aid in the interpretation of data on microstructural stability, phase equilibria, and creep resistance. Phases of MC (M: mainly Nb), M 23 C 6 (M: mainly Cr), B2 [b-(Ni,Fe)Al], and Laves [Fe 2 (Mo,Nb)] were observed after creep-rupture testing at 750°C and 170 MPa; this was generally consistent with the thermodynamic calculations. The creep resistance increased with increasing Nb additions up to 1 wt pct in the 2.5 and 3 Al wt pct alloy series, due to the stabilization of nanoscale MC particles relative to M 23 C 6 . Additions of Nb greater than 1 wt pct decreased creep resistance in the alloy series due to stabilization of the Laves phase and increased amounts of undissolved, coarse MC, which effectively reduced the precipitation of nanoscale MC particles. The additions of Al also increased the creep resistance moderately due to the increase in the volume fraction of B2 phase precipitates. Calculations suggested that optimum creep resistance would be achieved at approximately 1.5 wt pct Nb in the 4 wt pct Al alloy series.

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Section: Discussionmentioning

confidence: 99%

Effect of Alloying Additions on Phase Equilibria and Creep Resistance of Alumina-Forming Austenitic Stainless Steels

Yamamoto

Santella

Brady

et al. 2009

Metall Mater Trans A

102

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“…[22][23][24] The anomalously high stress exponents are consistent with the behavior of many precipitation-and dispersion-strengthened materials. [25][26][27][28][29] In these materials, the second-phase particles exert a resistive force on dislocation, also termed a "back stress" or internal stress. Thus, the actual creep stress is equal to the applied stress minus the internal resisting stress.…”

Section: Threshold Stress Analysismentioning

confidence: 99%

“…Several studies have invoked the concept of threshold stress in precipitation-strengthened alloys and dispersion-strengthened alloys to explain the high apparent stress exponent values and high apparent values for activation energy. [25][26][27][28][29] We have used this approach here to calculate the actual stress exponents and explain the creep mechanisms taking place. In the Sn-Ag eutectic system, Ag 3 Sn particles are considered stable with respect to the Sn-matrix.…”

Section: Threshold Stress Analysismentioning

confidence: 99%

“…Extensive studies have been carried out in GBS behavior of Pb-Sn solders. 29,[38][39][40] Since Sn-Pb solders have a lamellar microstructure consisting of two relatively soft, co-deforming phases, GBS is quite predominant during monotonic and creep deformation. The contribution of GBS to the total creep strain can be quantified as follows.…”

Section: Grain Boundary Slidingmentioning

confidence: 99%

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Effects of cooling rate on creep behavior of a Sn-3.5Ag alloy

Ochoa

Deng

Chawla

2004

Journal of Elec Materi

106

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The effect of cooling rate on microstructure and creep behavior of bulk, eutectic Sn-3.5Ag solders was studied. The cooling rate is an important processing variable that significantly affects the microstructure of the solder and therefore determines its mechanical behavior. Controlled cooling rates were obtained by cooling specimens in different media: water, air, and furnace, which resulted in cooling rates of 24°C/s, 0.5°C/s, and 0.08°C/s, respectively. The cooling rate decreased the secondary dendrite arm size and the spacing of the Sn-rich phase, as well as the morphology of Ag 3 Sn. The Sn-dendrite arm size and spacing were smaller at fast cooling rates, while slower cooling rates yielded a nearly eutectic microstructure. The morphology of Ag 3 Sn also changed from relatively spherical, at faster cooling rates, to needlelike for slower cooling. The effect of cooling rate on creep behavior was studied at 25°C, 60°C, 95°C, and 120°C. Faster cooling rates were found to increase the creep strength of the solder due to the refinement of the solder microstructure. Stress exponents, n, indicated that dislocation climb was the controlling mechanism. Activation energies, for all cooling rates, indicated that the dominant diffusional mechanism corresponded to dislocation pipe diffusion of Sn. Grain boundary sliding (GBS) measurements were conducted, using both scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was observed that GBS had a very small contribution to the total creep strain.

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“…Microstructural aspects [26,27,28] , and the tensile, [25,27,29,30] creep, [29,31] and oxidation behaviors of these alloys [32] have been studied. They possess excellent oxidation resistance due to the formation of an adherent film of Al 2 O 3 on the surface following high-temperature exposure.…”

Section: Introductionmentioning

confidence: 99%

Effect of prior oxidation on the creep behavior of NiAl-hardened austenitic steel

Satyanarayana

Malakondaiah

Sarma

2003

Metall Mater Trans A

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The effect of prior oxidation at 1473 K on the creep behavior of an Fe-Ni-Cr-Al alloy, hardened by ordered NiAl precipitates, has been investigated at 873 K over a stress range of 275 to 450 MPa. The alloy in the as-electroslag remelted (ESR) as well as the ESR-plus-hot-worked conditions was considered. Prior oxidation causes creep strengthening in the Fe-Ni-Cr-Al alloy, resulting in a decrease in minimum creep rate and increase in time to rupture, in contrast to the observations reported on nickel-based superalloys. Creep strengthening is, however, accompanied by a significant reduction in creep ductility. Oxidation-induced creep strengthening in the current alloy can be attributed to the improved adherence of surface oxide caused by the presence of yttrium. An effective stress that incorporates the contributions of load transfer as well as substructural strengthening is used to account for the observed oxidation-induced creep strengthening. While creep strengthening is more pronounced in the ESR cast alloy, the loss in creep ductility is more intense in the ESR wrought alloy. Increasing the oxidation time beyond 1 hour has a minimal effect on creep strengthening of both the alloys, though it lowers significantly the creep ductility of the wrought alloy. The observed differences in creep behavior of the alloy in the two different conditions could be attributed to the differences in grain size as well as morphology and related oxidation-induced damage.

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Steady state creep behaviour of NiAl hardened austenitic steel

Cited by 66 publications

References 28 publications

Effect of Alloying Additions on Phase Equilibria and Creep Resistance of Alumina-Forming Austenitic Stainless Steels

Effect of Alloying Additions on Phase Equilibria and Creep Resistance of Alumina-Forming Austenitic Stainless Steels

Effects of cooling rate on creep behavior of a Sn-3.5Ag alloy

Effect of prior oxidation on the creep behavior of NiAl-hardened austenitic steel

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