Metallurgy of Microalloyed 24 Carat Golds

Corti, Christopher W.

doi:10.1007/bf03214789

Cited by 42 publications

(25 citation statements)

References 7 publications

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“…For example, Y2O3 has larger negative ⌬GT 0 value than that of Al2O3 in the range of 0~1400°c. So the oxides of rare earths are stable in gold alloys and can lead to strengthening when they are distributed as a dispersed phase (1,8). Dispersion strengthened gold alloys can be prepared by powder metallurgy for bulk material and by internal oxidation for foil and superfine wire of gold alloys.…”

Section: 3mentioning

confidence: 99%

Properties and applications of some gold alloys modified by rare earth additions

Yuantao

2005

Gold Bull

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IntroductionAs we know, gold is soft and can be strengthened through alloying. The conventional alloying elements typically used include silver (Ag), copper (Cu), nickel (Ni), platinum (Pt), palladium (Pd), manganese (Mn) and chromium (Cr). Of these, Ag, Cu and Ni are the main strengthening elements, and Mn and Cr are used mainly as resistance-sensitive elements. Gold can also be strengthened by microalloying (1). Of the possible microalloying elements, rare earth (RE) metals are very effective strengthening agents for both pure gold and gold alloys (2). In the present paper, the influence of RE additions on some properties of gold and gold alloys, such as Au-Ni, Au-Ni-Cr, Au-Ag-Cu and Au-Ag-Cu-Mn, have been studied and applications of such RE-modified gold alloys are reported.

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Section: 3mentioning

confidence: 99%

Properties and applications of some gold alloys modified by rare earth additions

Yuantao

2005

Gold Bull

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“…In bleach the corrosion potential is at 0.7 V. In the caustic soda solution the sample shows a distinct active corrosion region prior to reaching a pseudopassive region where the value of the current density does not increase much beyond 0.005 mA/cm 2 . Passivation occurs at approximately 1.1 V followed shortly by active corrosion at 1.23 V. The sample in hydrochloric acid shows a distinct active corrosion region prior to a pseudo-passive region at approximately 0.017 mA/cm 2 . At E c = 1.25 V, the caustic soda and hydrochloric acid samples show a significant increase in current density accompanied by formation of a grayish surface film.…”

Section: Experimental Methodsmentioning

confidence: 92%

“…However, pure gold (locally known as 'Chuk Kam') jewelry is dominant in the Chinese region of Asia (2). In other parts of the world, it is more common to find gold alloyed with other metals including copper, nickel, palladium, and silver to increase its strength and hardness.…”

Section: Introductionmentioning

confidence: 99%

Environmentally Induced Failure of Gold Jewelry Alloys

2005

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Stress corrosion cracking (SCC) is an established form of environmental attack in low karatage gold jewelry alloys. The cause of failure is often attributed to exposure to chlorinated solutions. At a certain gold content (usually greater than 14K) the alloy is widely believed protected from SCC. In this study, three commercial 18K gold alloys (yellow gold, nickel white gold, and palladium white gold) were tested in combination with three different household solutions to determine relative corrosion rates. These rates were determined using polarization tests. Once the maximum corrosion rate had been established, SCC tests using the constant potential dead weight method were used to determine time to failure. The resultant failure surfaces were examined to determine mode of fracture, which in all cases was predominantly intergranular. It was found that corrosion rates depended upon both the alloy system and the test solution. SCC was clearly demonstrated in 18K gold alloys, although in all cases times to failure were significantly greater than has been reported for lower karatage alloys. Palladium white gold was far more resistant to SCC than the other systems studied.

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“…Therefore, it is necessary to introduce some other mechanisms of alloy strengthening, such as introduction of alloying elements, which are very different to gold in atomic radius and have lower density, or the use of elements with very low solubility in gold matrix. One such approach is the microalloying of gold with rare earth elements as suggested by theoretical analysis [5] and in our study we decided for lanthanum. Microalloying with lanthanum can serve as deoxidants to facilitate bonding between the alloy and the ceramic or to enhance the strength and colour of the alloy [9].…”

Section: Introductionmentioning

confidence: 99%

“…The mechanical properties of pure gold can also be improved significantly by microalloying [5][6][7]. In recent years, significant effort has been made to increase the hardness of 24-carat gold alloys with a minimum of 99.5 wt% of Au [8], but such alloys exhibit only slightly higher hardness than pure gold in an annealed state.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and biocompatibility of gold–lanthanum strips

et al. 2014

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Microalloying of pure gold, which has the highest biocompatibility but relatively low yield strength and poor wear resistance, might improve its applicability as adornments and biomedical implants. The objective of this study was to analyse the microstructure and biocompatibility of gold-lanthanum (Au-0.5 wt% La) microstrips as a potential biomaterial in dentistry or medicine. We found that microalloying of Au with La produced very fine nanosized grains homogeneously dispersed through the entire volume of the rapidly solidified (RS) alloys. This initiates the formation of Au 6 La phase which increases strength and hardness of the alloy significantly. By RS, large reduction of grains and microsegregation increases the strength of the alloy additionally. Our results suggest that Au-La microstrips, although non-cytotoxic for L929 cells, rat thymocytes, rat peritoneal macrophages (PMØ) and human peripheral blood mononuclear cells (PBMNCs), can activate immune cells. Namely, RS Au-La microstrips stimulated the production of nitric oxide (NO) by PMØ. Using a model of phytohemaglutinine (PHA)-stimulated human PBMNCs, we found that RS Au-La strips increased the proliferation of these cells and stimulated the production of Th1, Th17 cytokines, and immunoregulatory cytokine IL-10. Our results suggest that RS Au-La microstrips are biocompatible, but they can modulate the immune response. Therefore, their use as potential implants should be considered carefully.

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Metallurgy of Microalloyed 24 Carat Golds

Cited by 42 publications

References 7 publications

Properties and applications of some gold alloys modified by rare earth additions

Properties and applications of some gold alloys modified by rare earth additions

Environmentally Induced Failure of Gold Jewelry Alloys

Microstructure and biocompatibility of gold–lanthanum strips

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