Ostwald ripening of spheroidal particles in multicomponent alloys

Kim, Kyoungdoc; Voorhees, Peter W.

doi:10.1016/j.actamat.2018.04.041

Cited by 62 publications

(18 citation statements)

References 21 publications

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“…The samples tempered at 500 and 760 °C are not included in Figure because of the small amount, the large aspect ratio and interconnection of M 23 C 6 phase, respectively. Average sizes of M 23 C 6 increase with increasing tempering temperature from about 36 nm at 600 °C/2 h to 85 nm at 730 °C/2 h and 94 nm at 730 °C/5 h. The coarsening process of particles is known to follow the Ostwald ripening equation:

r^{3} - r_{0}^{3} = K_{p} t

where r and r 0 are the average particle radius and the initial average particle radius, respectively. In a C‐component system of β precipitate particles in a α matrix, K p is given as follows:

K_{p} = \frac{8}{9} \frac{γ V_{m}^{β}}{\sum_{i = 1}^{c} \frac{{(x_{i}^{β} - x_{i}^{α / β})}^{2}}{x_{i}^{α / β} D_{i} / RT}}

where γ is the interfacial energy,

V_{m}^{β}

the molar volume of the particle, D i the diffusion coefficient,

x_{i}^{β}

the mole fraction of element i in the particle,

x_{i}^{α / β}

the mole fraction of element i at the particle/matrix interface, T the temperature and R the gas constant.…”

Section: Discussionmentioning

confidence: 99%

“…The density of dislocation decreases as increase tempering temperature and prolong exposure duration. However, the solid solution strengthening alloying elements Nb, V, and Mo et al greatly retard the annihilation of dislocations due to their high activation energies for diffusion . Meanwhile, the fine precipitates distributed within the laths and along the subgrains such as M 23 C 6 , MX in the steel can effectively hider dislocation migration and exert a pinning force against the movement of subgrain boundaries .…”

Section: Discussionmentioning

confidence: 99%

“…The samples tempered at 500 and 760 C are not included in Figure 9 because of the small amount, the large aspect ratio and interconnection of M 23 C 6 phase, respectively. Average sizes of M 23 C 6 increase with increasing tempering temperature from about 36 nm at 600 C/2 h to 85 nm at 730 C/2 h and 94 nm at 730 C/5 h. The coarsening process of particles is known to follow the Ostwald ripening equation [24,25] :…”

Section: Discussionmentioning

confidence: 99%

“…However, the solid solution strengthening alloying elements Nb, V, and Mo et al greatly retard the annihilation of dislocations due to their high activation energies for diffusion. [25] Meanwhile, the fine precipitates distributed within the laths and along the subgrains such as M 23 C 6 , MX in the steel can effectively hider dislocation migration and exert a pinning force against the movement of subgrain boundaries. [5] The transverse sizes of martensite laths of the steel with different conditions are presented in Table 1.…”

Section: Discussionmentioning

confidence: 99%

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Microstructure Evolution in an Advanced 9Cr–1.5Mo–1Co–VNbBN Alloy during Heat Treatment and High Temperature Aging

Gao

Zhang

Ren

et al. 2019

steel research int.

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The 9Cr–1.5Mo–1Co–VNbBN steel is the most successful cast steel developed so far in the COST program. Its microstructure evolution influenced by austenitizing and tempering are investigated in this paper. The microstructure characterization using an optical microscope and transmission electron microscope is carried out after different heat treatments and long‐term aging at 620 °C. After austenitization at 1100 °C, the steel exhibits a martensite structure with Fe‐rich M3C particles. The M23C6 particles are detected in the sample tempered at 500 °C for 2 h, as well as their sizes continue to grow as the tempering temperature raise. The formation of MX phase is identified after tempering at 500 °C, while the size of MX phase remains stable within the tempering temperature 760 °C and below. The structure evolution of martensitic laths shows that tempering reduces the density of dislocation and forms subgrains and dislocation networks. The microstructure of long‐term aged sample still reveals martensite lath structure with increasing width. In addition to M23C6 and MX phases, Laves phase nucleates and grows rapidly as a result of long‐term aging.

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r^{3} - r_{0}^{3} = K_{p} t

where r and r 0 are the average particle radius and the initial average particle radius, respectively. In a C‐component system of β precipitate particles in a α matrix, K p is given as follows:

K_{p} = \frac{8}{9} \frac{γ V_{m}^{β}}{\sum_{i = 1}^{c} \frac{{(x_{i}^{β} - x_{i}^{α / β})}^{2}}{x_{i}^{α / β} D_{i} / RT}}

where γ is the interfacial energy,

V_{m}^{β}

the molar volume of the particle, D i the diffusion coefficient,

x_{i}^{β}

the mole fraction of element i in the particle,

x_{i}^{α / β}

the mole fraction of element i at the particle/matrix interface, T the temperature and R the gas constant.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Microstructure Evolution in an Advanced 9Cr–1.5Mo–1Co–VNbBN Alloy during Heat Treatment and High Temperature Aging

Gao

Zhang

Ren

et al. 2019

steel research int.

View full text Add to dashboard Cite

show abstract

“…Thus, two processes are performed simultaneously during the heat preservation process, namely the growth of the γ′ phase and the re-dissolution of the γ′ phase. The growth of the γ′ phase follows the Ostwald Ripening [29][30][31]. At a certain temperature, the matrix has reached saturation for larger particles, but not for small particles.…”

Section: Microstructure Evolution Mechanism Of As-cast Alloy During Smentioning

confidence: 97%

Microstructure evolution of DD6 during different heat treatment conditions

Huang

Zhao

et al. 2019

Mater. Res. Express

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001] oriented DD6 alloy was prepared by directional solidification in this experiment. γ′ phase precipitation phase structure of different morphology and size was obtained by different high temperature ageing heat treatment processes. Through this experiment, the feasibility of improving high temperature performance by adjusting the heat treatment process to change the microstructure of the single crystal was explored. The as-cast DD6 is first subjected to standard heat treatment(SHT). The single crystal sample after the standard heat treatment was further kept at 900°C-1300°C for 10 min, 30 min and 1 h, finally air-cooled respectively. Heat treatment process of DD6 was simulated using Jmatpro software. The individual phase transition temperatures of the alloy were determined by DSC experiments. And the size and volume fraction of precipitated phase of the alloy were estimated using Image-Pro Plus software. It is concluded that the microstructure of the alloy obtained after holding at 1100°C for 30 min after standard heat treatment has the most uniform microstructure distribution.

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