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Mechanical Behavior of a Pt-Cr Jewelry Alloy Hardened by Nano-Sized Ordered Particles

Published online by Cambridge University Press:  26 February 2011

Kamili M. Jackson ,
Miyelani P. Nzula ,
Silethelwe Nxumalo  and
Candace I. Lang
Kamili M. Jackson
Affiliation:
University of Cape Town, Mechanical Engineering Department, Centre for Materials Engineering
Miyelani P. Nzula
Affiliation:
University of Cape Town, Mechanical Engineering Department, Centre for Materials Engineering
Silethelwe Nxumalo
Affiliation:
University of Cape Town, Mechanical Engineering Department, Centre for Materials Engineering
Candace I. Lang
Affiliation:
University of Cape Town, Mechanical Engineering Department, Centre for Materials Engineering
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Abstract

The materials engineering of platinum jewelry is interesting because only 5wt% can be used for alloying in order to maintain hallmarking. However, pure platinum is very soft and must be alloyed in order to be used effectively as jewelry. In several binary systems an increase in hardness has been found after cold working and annealing at low temperatures. The hardening in these alloys has shown to be a result of nano-sized ordered particles. In particular, the existence of the ordered particles has previously been confirmed for a Pt-Cr alloy by TEM. Extensive work has been done on the Pt-Cr alloy to understand the crystal structure and mechanisms of the ordered phase. Hardness tests were performed to measure mechanical properties after various heat treatments. In addition, tensile tests were conducted using a small-scale tensile testing machine. An 8mm long specimen is used, which significantly reduces the cost of the specimens while providing necessary properties. Tensile tests on the Pt-Cr alloys at various post deformation heat treatments show an increase in tensile strength with no effect on ductility. They confirm results of the hardness tests while providing additional properties data. In addition, the results show a fairly good relationship between strength and hardness.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 842: Symposium S – Integrative and Interdisciplinary Aspects of Intermetallics , 2004 , S5.52
Copyright
Copyright © Materials Research Society 2005

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References

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