ISSN (print) 1995-2732
ISSN (online) 2412-9003


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Platinum is one of the most precious metals in the world: 15 times rarer than gold and it is widely used in jewellery for its characteristic of unicity, incorruptibility, and colour neutrality. The standard grade in the jewellery industry is Platinum 950‰. In fact, pure platinum jewels are easily scratched, due to the poor hardness linked with the high purity. Among all the commercial alloys available, the Pt-Ru system is the one characterized by the highest mechanical properties. Aim of this work is to find an ideal softening heat treatment, in term of operating time and temperature. The heat treatment must be able to satisfy two main needs: it must permit to complete recrystallization of the work piece, preparing the material for further severe deformation by restoring high ductility and an equiaxed grain distribution; and at the same time, the final average grain size must be fine, in order to avoid counter side aesthetic effects that occur when grain size go over the micrometric scale. Due to its rarity, in literature there are few information about the alloy under discussion. To find the optimal parameters, several samples had been heat treated at different times and temperatures. Then they had been analysed by optical microscopy and with micro hardness tests, providing microstructure images and hardness data. By using a combination of three different temperatures and three different times, significant differences were found between the various samples both in terms of mechanical properties and of grain size. The comparison of the collected data permit to better understand the behaviour of the alloy under recrystallization conditions. In the end, it was observed that the dynamics of recrystallization changes significantly with relative small changes of temperature and was found that the optimal treatment to obtain a fine recrystallized microstructure with the desired mechanical properties is at 1000°C for 15 minutes.


Platinum alloy, softening heat treatment, jewellery, microhardness, microstructure.

Luca Pezzato, Alessandro Minotto, Katya Brunelli, Manuele Dabalà

Department of industrial Engineering, University of Padua, Padova, Italy

1. Gold Demand Trends Q3 2016. World Gold Council, 8th November 2016

2. T. Biggs. The Hardening of Platinum Alloys for Potential Jewellery Application. Platinum Metals Rev., 2005, 49, (1), 2–15

3. G. Rakhtsaum. Platinum Alloys: A Selective Review of the Available Literature. Platinum Metals Rev., 2013, 57, (3), 202–213

4. K.M. Jackson, C. Lang. Mechanical Properties Data for Pt-5 wt.% Cu and Pt-5 wt.% Ru Alloys. Platinum Metals Rev., 2006, 50, (1)

5. S. Tedesco. Manuale di tecnologia e lavorazione del platino, Atti del congresso Tecno Platino, Vicenza 8 Luglio 1999.

6. J.C. Wright. Jewellery related properties of platinum. Platinum Metals Rev., 2002, 46, (2)

7. G. Normandeau, D. Ueno. Understanding Heat treatable Platinum Alloys. “The Santa Fe Symposium on Jewelry Manufacturing Technology 1999”, Proceedings of the 13th Santa Fe Symposium in Albuquerque, New Mexico, USA, ed. D. Schneller, Met-Chem Research, Albuquerque, New Mexico, USA, 1999, 73–103

8. C. Mshumi, C. Lang. Strenghtening of Platinum-5wt% Copper by Heat Treatment.. Platinum Metals Rev., 2007, 51, 78–82