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The age hardenability of 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) alloyed with titanium

Abstract

The age hardenability of 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) alloyed with Ti at various concentrations (0.5, 0.75, and 1 wt.%) was studied. The addition level of Ti is compensated with Ag to maintain the purity of gold in 22 karat, i.e., 91.75 wt.%. The Ti containing 22 karat gold was prepared by melting Au, Cu, and Ag and adding Ti via Au-6wt.%Ti master alloy. The castings obtained were cold-rolled into thin sheet (90% reduction). Both the cast and cold-rolled sheets were subjected to age hardening treatment (solutionizing and artificial aging). Artificial aging was performed as a function of time at 550 °C to identify the peak aging. At all addition level of Ti, the 22 karat gold responded well to the age hardening treatment. The cold-worked sheet samples showed faster peak aging within 30 min. and higher peak hardness than their cast counterpart. Increasing the Ti concentration increases the peak hardness of both cold-rolled sheet and casting samples. Transmission electron microscopic analysis of the peak aged cold-rolled sheet samples shows uniformly distributed coherent Au4Ti precipitates in Au matrix which contribute to the higher hardness.

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Acknowledgements

The authors wish to thank, Mr. S. Santhosh and Mr. Sanjay Ranawade of Titan Company Ltd (Jewelry Division), Hosur, Tamilnadu, India, for supporting this work by supplying 24 karat gold (99.99wt.% pure).

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Correspondence to G. S. Vinodkumar.

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Saradesh, K.M., Ravi, K.R. & Vinodkumar, G.S. The age hardenability of 22 karat gold (Au-5.8wt.%Cu-2.5wt.%Ag) alloyed with titanium. Gold Bull 54, 105–113 (2021). https://doi.org/10.1007/s13404-021-00301-9

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Keywords

  • 22 karat gold
  • Titanium
  • Age hardening
  • Au-Ti equilibrium diagram
  • Au4Ti intermetallic