Platinum based bulk metallic glasses for jewelry applications
Ulrich E. Klotz
The paper presents a new class of metallic platinum alloys with very different properties compared to
conventional platinum alloys. Precious based bulk metallic glasses (BMG) are interesting materials for
jewelry and watch making applications due to their special properties such as high as-cast hardness,
good corrosion resistance, and outstanding surface quality. However, high critical cooling rates are
required to achieve amorphous solidification, which implies challenges for their manufacturing. So far
such alloys were only melted under laboratory condition and could not have been produced by
industrial investment casting. Instead, they are cast in metallic molds, which strongly limits the
geometric complexity of cast parts.
This paper, for first time demonstrates the successful investment casting into conventional ceramic
molds, which allows a much more flexible production of BMG parts, thereby enabling the application
in the jewelry and watch industry. The present work focuses on the process development for
investment based casting of Pt-P-Cu based BMGs in order to allow for jewelry casting on an industrial
scale. The results of centrifugal and vacuum-die casting applied for two different alloys are presented.
One of the alloys contains 74wt% Platinum and shows a high glass forming ability, whereas the other
alloy has 85wt% Platinum with a significantly less glass forming ability. Cast filigree jewelry parts with
an outstanding surface quality and extremely high elasticity have been demonstrated.