The formation of discrete precipitate dispersions on mobile interphase boundaries in iron-base alloys

Ricks, R. A.; Howell, P. R.

doi:10.1016/0001-6160(83)90113-x

Cited by 100 publications

(51 citation statements)

References 18 publications

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“…interface by fast boundary diffusion in the moving ledge interface. As we will see, it is also possible to combine the quasi-ledge mechanism proposed by Ricks and Howell [11] for interphase precipitation occurring in curved, incoherent that is consistent both with the microscopic observations upon which the models by Honeycombe and Ricks and Howell are founded and with the observed intersheet spacings and their dependence on temperature and alloying conNevertheless, once the diffusion coefficient has been adjusted, the model based on volume diffusion would be tents. The explanation of the latter dependencies has been the particular target of the work by the present authors.…”

Section: Model For Interphasesupporting

confidence: 68%

“…It is, where the meaning of the symbols c ␣ V , c 0 V , c ␣ /VCN V , x, and however, well demonstrated that interphase precipitation are given in Figure 9, and with regular intersheet spacings may also occur in incoherent, often-curved ␥ /␣ boundaries. [11] The principal difference a ϭ 4 2 (D␦) boundary [8] between this case and the case of semicoherent interfaces discussed previously arises when the bulge has bowed out where is the velocity of the ␥ /␣-interface superledge and sufficiently for a new precipitate sheet to be nucleated (point (D␦) boundary is the diffusion coefficient in the interface. The N in Figure 9).…”

Section: Model For Interphasementioning

confidence: 85%

“…[4] and [8], we find that the model of intersheet spacing and particle spacing in the sheet with predicts the intersheet spacing to increase with the square the distance of ferrite growth ( Figure 15). If we make the root of the distance of ferrite growth, according to the followreasonable assumption that interphase precipitation will not ing expression: be recognizable unless Ն 3⌳ (Figure 15), interphase precipitation will only be observed for S values larger than ϭ a(D␦ ) boundary S 2K 1 1/2 [11] about 6000 nm. For a ferrite grain size of 10 m, this implies that we should expect a variation for from about 85 to 110 nm, From the reasoning leading to Eq.…”

Section: Predictions Of the Model Based Onmentioning

confidence: 99%

“…However, later, Ricks and Howell developed the ledge concept further to explain the formation of interphase precipitation in incoherent, often curved ␥ /␣ boundaries, usually called the quasi-ledge mechanism. [11] One of the main drawbacks of the ledge mechanism is its inability to produce a credible explanation of the observed (a) (b) variation of the intersheet spacing with temperature and steel composition, especially N, V, and C. It is hard to see how Among the models based on diffusion control, the solute-0.12V-0.026N. [2] depletion model proposed by Roberts [12] is the most prominent and promising one, as it appears to the present authors.…”

Section: Introductionmentioning

confidence: 99%

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A model for interphase precipitation in V-microalloyed structural steels

Lagneborg

Zając

2001

Metall Mater Trans A

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A model for interphase precipitation, with a predictive capacity, is presented. This article deals with its application to V-microalloyed steels. The model rests on an analysis of the growth of the Vdepleted zone ahead of a sheet of V(C,N) particles and the simultaneous advance of the ␥ /␣ interface in which it was nucleated. It is shown that volume diffusion of V cannot explain the observed intersheet spacings and that a faster diffusion process is required. It is postulated that the ␥ /␣ boundary will bow out some time after a sheet of V(C,N) particles has formed in it. Part of the V in the ␥ will then be fed to V(C,N) particles in the sheet by boundary diffusion as the ␥ transforms to ␣. The V content at the front will, thus, be lower than the initial content in the austenite. However, the reduction will be less the further the interface has moved away from the sheet of V(C,N) particles. At a sufficient distance, the V content is again high enough to allow new V(C,N) particles to nucleate, and a new sheet of particles will form. Between the two sheets, there will be a ledge (or superledge) that will advance along the first sheet. The height of the ledge will, thus, be determined by the distance in which V(C,N) particles can again be nucleated. The model exhibits reasonably good agreement with observed values of intersheet spacing, with its temperature dependence and transition from interphase to general precipitation, and with its dependence on C, V, and N content. It also provides physically sound explanations of these dependencies. I. BACKGROUNDsome high-temperature region where the chemical driving force for precipitation is low, nature chooses the sites where THE precipitation of V carbonitrides in V-microalloyed nucleation is energetically most favored, viz., the interface. steels can occur either randomly in ferrite in the wake of At lower temperatures where the driving force is large, we the migrating austenite-ferrite (␥ /␣) interface (general premight expect general nucleation in the ferrite matrix to occur. cipitation) or by interphase precipitation characterized by At high transformation temperatures, ϳ800 ЊC, for typical the development of sheets of particles parallel to the ␥ /␣ compositions of V-microalloyed structural steels, the interface formed repeatedly, with rather regular spacing.interphase precipitation consists of irregularly spaced and Many investigations have shown that, for compositions typioften curved sheets of V(C,N) particles. With decreasing cal of V-alloyed structural steels, the general precipitation temperatures, the occurrence of curved rows of precipitates takes place at lower temperatures, typically below 700 ЊC, diminishes and the dominant mode is regularly spaced, plaand the interphase precipitation takes place at higher nar sheets of particles (Figure 1). Below about 700 ЊC, temperatures.the interphase precipitation is commonly found to be less Figure 1 shows the typical morphology of interphase prefrequent, and random precipitation from supersaturated fercipitation of V...

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Section: Model For Interphasesupporting

confidence: 68%

Section: Model For Interphasementioning

confidence: 85%

Section: Predictions Of the Model Based Onmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A model for interphase precipitation in V-microalloyed structural steels

Lagneborg

Zając

2001

Metall Mater Trans A

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“…[3][4][5] However, one drawback of these steels is their small post-uniform elongation due to the large difference in strength between the ferrite and martensite phases. In contrast, nano-precipitated ferrite steels produced by interphase precipitation 6,7) are well known commercial steels having both high strength and good formability. 8,9) This type of steel has a structure consisting of single phase ferrite containing a dispersion of nano-sized alloy carbides.…”

Section: Introductionmentioning

confidence: 99%

Tensile Behavior of Ferrite-martensite Dual Phase Steels with Nano-precipitation of Vanadium Carbides

et al. 2015

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This paper reports the effect of nano-precipitation strengthening of ferrite on the tensile behavior of ferrite-martensite dual phase (DP) steels. Samples of ferrite-martensite DP steel containing a dispersion of nano-sized vanadium carbides (VCs) in the ferrite phase were produced by interphase precipitation and quenching of a V-added low carbon steel, and the mechanical properties are compared with those of conventional ferrite-martensite DP samples without VC particles. Both the yield stress and the ultimate tensile strength are significantly increased by nano-VC precipitates. For ferrite volume fractions of 20-50% a dispersion of VCs results in only a small change in the elongation, whereas for ferrite volume fractions of above 50% both uniform and post-uniform elongations are decreased by a VC dispersion. It is suggested that dispersion of nano-precipitates in ferrite is an effective approach to simultaneously improve the strength and the strength-ductility balance of DP steels. Digital image correlation (DIC) analysis demonstrates that the ferrite phase is more deformed than the martensite phase in both VC-free and VC-dispersed DP samples, but that such strain partitioning is less pronounced in the VC dispersion-hardened samples. It is found that the stress-strain relationship of DP samples can reasonably be explained based on a law of mixtures using partitioned strain and stress values as estimated from the DIC analysis.KEY WORDS: dual phase (DP) steel; interphase precipitation; vanadium carbides (VC); mechanical property; digital image correlation (DIC); strain and stress partitioning.

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The Effect of Strain in Recrystallization Region on Interphase Precipitation and Mechanical Properties of Ferritic Microalloyed Steels

et al. 2022

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High yield strength (710–862 MPa) ferritic microalloyed steels are developed through the combined contribution of Nb, Mo, V, and Cr microalloying and controlled thermomechanical treatment. Microstructures and mechanical properties are characterized using advanced microscopy techniques and uniaxial tensile testing. NbV carbonitrides with/without Mo (depending on steel composition) are formed in austenite and range from 30 to 70 nm in average diameter. However, V‐ and Cr‐rich interphase (3–7 nm range) and random (1–6 nm range) precipitates are found in polygonal ferrite. An increase in roughing strain in the recrystallization region results in finer polygonal ferrite grains, higher number density of NbV carbonitrides and VCr interphase precipitates, and their size reduction. Higher roughing strain also minimize the intersheet spacing of interphase precipitates. Finer polygonal ferrite grains and a greater number of nanosized interphase precipitates are responsible for the higher yield strength of 862 MPa in the VCrNb steel processed with a larger strain in the recrystallization region.

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The formation of discrete precipitate dispersions on mobile interphase boundaries in iron-base alloys

Cited by 100 publications

References 18 publications

A model for interphase precipitation in V-microalloyed structural steels

A model for interphase precipitation in V-microalloyed structural steels

Tensile Behavior of Ferrite-martensite Dual Phase Steels with Nano-precipitation of Vanadium Carbides

The Effect of Strain in Recrystallization Region on Interphase Precipitation and Mechanical Properties of Ferritic Microalloyed Steels

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