Age-hardening behaviour of a spinodally decomposed low-carat gold alloy

Park, Mi-Gyoung; Yu, Chin-Ho; Seol, Hyo‐Joung; Kwon, Yong Hoon; Kim, Hyung-Il

doi:10.1007/s10853-007-2348-5

Cited by 15 publications

(20 citation statements)

References 11 publications

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“…Their inter-phase boundaries must have contained large amounts of internal strain due to the gap in the lattice parameter, resulting in constant hardening. The previous study with a dental Au-Ag-Cu alloy with relatively high Zn content reported a similar fine block-like structure 4 . Considering that the present alloy went through the same phase transformation process with the previous alloy except for further ordering of the Cu-rich phase to AuCu I, the common block-like structure appeared to be formed as a result of spinodal decomposition regardless of the tetragonality by the ordered AuCu I phase.…”

Section: Microstructural Changesmentioning

confidence: 60%

“…The effective range of aging temperature which can afford is restrictive, and thus the available age-hardening mechanism of the alloys also becomes restrictive. Regarding Au-Ag-Cu-based alloys, age-hardenability is related to phase separation into Ag-rich and Cu-rich phases, and the separated phases may or may not transform to an ordered phase with or without tetragonality, possibly through a metastable state [3][4][5][6][7] . In a previous study with a dental Au-Ag-Cu alloy with relatively high zinc content aged at 400 °C, the alloy was decomposed spinodally into Ag-rich and Cu-rich phases through a metastable state without subsequent ordering of the Cu-rich phase into the AuCu I phase.…”

Section: Introductionmentioning

confidence: 99%

“…The hardness increased from 200 (HV) to 250 (HV) within very short time periods (e.g. 12 seconds) owing to spinodal decomposition, and then increased constantly to 280 (HV) up to 5000 minutes 4 . Considering the above study, it can be thought that if the alloy went through the subsequent ordering into the AuCu I phase after spinodal decomposition, the alloy would have more apparent age-hardenenability.…”

Section: Introductionmentioning

confidence: 99%

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Age-hardenability and related microstructural changes during and after phase transformation in an Au-Ag-Cu-based dental alloy

Kim

et al. 2012

Mat. Res.

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The aim of this study was to clarify how the microstructural changes during and after phase transformation determine the age-hardenability of an Au-Ag-Cu-based dental alloy. The rapid increase in hardness in the initial stage was the result of rapid atomic diffusion by spinodal decomposition into metastable Ag-rich' and Cu-rich' phases. The constant hardening after apparent initial hardening was the result of a subsequent transformation of the metastable Ag-rich' and Cu-rich' phases to the stable Ag-rich α 1 phase and AuCu I phase through the metastable AuCu I' phase. During the increase in hardness, fine block-like structure with high coherency formed in the grain interior, which changed to a fine cross-hatched structure. A relatively coarse lamellar structure composed of Ag-rich α 1 and AuCu I phases grew from the grain boundaries, initiating softening before the grain interior reached its maximum hardness. As a result, the spinodal decomposition attributed to rapid hardening by forming the fine block-like structure, and the subsequent ordering into AuCu I, which is a famous hardening mechanism, weakened its hardening effect by accelerating the lamellar-forming grain boundary reaction.

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Section: Microstructural Changesmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Age-hardenability and related microstructural changes during and after phase transformation in an Au-Ag-Cu-based dental alloy

Kim

et al. 2012

Mat. Res.

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“…2). By aging for 30 s when the hardness increased apparently, broad peaks of Ag-Au-rich and Cu-Au-rich were observed at both sides of the parent α 0 phase, and there was no characteristic side-band by spinodal decomposition [7]. In the present study, the alloy is mainly composed of the AuAg-Cu system, in which Ag and Cu have a miscibility limit, while Au has complete miscibility with Ag and Cu in the solid state [9].…”

Section: Phase Transformationmentioning

confidence: 99%

“…In a study on the age-hardening mechanism of a 55Au-19.9Ag-17Cu-4Zn-3Pd (wt.%) alloy aged at 400°C, the spinodal decomposition of the parent phase into the Ag-rich phase and the Cu-rich phase occurred in an instant, and causing a rapid increase in hardness and an apparent delay in softening due to the uniform fine spinodal structure [7]. The formation of the metastable phase was apparent only for the Ag-rich phase in the alloy, which was thought to have resulted from the fact that the gap in the lattice parameter between the parent phase and the final Ag-rich phase was twice larger than that between the parent phase and the final Cu-rich phase.…”

Section: Introductionmentioning

confidence: 99%

Age-hardening and overaging mechanisms related to the metastable phase formation by the decomposition of Ag and Cu in a dental Au–Ag–Cu–Pd–Zn alloy

et al. 2011

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The age-hardening and overaging mechanisms related to the metastable phase formation by the decomposition of Ag and Cu in a dental casting gold alloy composed of 56Au-25Ag-11.8Cu-5Pd-1.7Zn-0.4Pt-0.1Ir (wt.%) were elucidated by characterizing the age-hardening behaviour, phase transformations, changes in microstructure and changes in element distribution. The fast and apparent increase in hardness at the initial stage of the aging process at 400°C was caused by the nucleation and growth of the metastable Ag-Au-rich phase and the Cu-Au-rich phase by the miscibility limit of Ag and Cu. The transformation of the metastable Ag-Au-rich phase into the stable Ag-Aurich phase progressed concurrently with the ordering of the Cu-Au-rich phase into the AuCu I phase through the metastable state, which resulted in the subsequent increase in hardness. The further increase in hardness was restrained before complete decomposition of the parent α 0 phase due to the initiation of the lamellar-forming grain boundary reaction. The progress of the lamellar-forming grain boundary reaction was not directly connected with the phase transformation of the metastable phases into the final product phases. The heterogeneous expansion of the lamellar structure from the grain boundary caused greater softening than the subsequent further coarsening of the lamellar structure. The lamellar structure was composed of the Ag-Au-rich layer which was Cu-, Pd-and Zn-depleted and the AuCu I layer containing Pd and Zn.

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Compositional Evolution of Oxide Inclusions in Austenitic Stainless Steel during Continuous Casting

Choi

Kim

Kang

et al. 2014

steel research int.

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Composition evolution and number density of oxide inclusions in austenitic stainless steel were investigated by analyzing inclusions in a commercial austenitic stainless steel slab. The composition of inclusions was observed to be strongly dependent on size of the inclusion and location in the slab, both, where the inclusions were found. The number density of inclusions increased as the inclusions were found at deeper location from the slab surface. The basicity (%CaO/%SiO 2 ) of the inclusions decreased with decreasing the inclusion size, while the manganese oxide content (%MnO) increased with decreasing the inclusion size. As the inclusions were located deeper from the slab surface, the basicity (%CaO/%SiO 2 ) was found decreased but (%MnO) increased. Such composition changes along with the position in the slab was attributed to the combination of pre-existing inclusions which were entrapped from the argon oxygen decaburization slag and inclusions precipitated during solidification due to decrease in solubility limit of concerned elements. A theoretical model was developed in order to represent the inclusion composition in the austenitic stainless steel during continuous casting, as a function of the size and location of the inclusion. The model predictions for the composition of inclusion, such as (%CaO/%SiO 2 ), (%MnO), and Al 2 O 3 content, were in good agreement with the measured data.

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Age-hardening behaviour of a spinodally decomposed low-carat gold alloy

Cited by 15 publications

References 11 publications

Age-hardenability and related microstructural changes during and after phase transformation in an Au-Ag-Cu-based dental alloy

Age-hardenability and related microstructural changes during and after phase transformation in an Au-Ag-Cu-based dental alloy

Age-hardening and overaging mechanisms related to the metastable phase formation by the decomposition of Ag and Cu in a dental Au–Ag–Cu–Pd–Zn alloy

Compositional Evolution of Oxide Inclusions in Austenitic Stainless Steel during Continuous Casting

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