Combinatorial Searching for Noble Metal-based Thin Film Amorphous Alloys for Glass Lens Mold

This paper presents the properties of Pt-based thin film amorphous alloys developed for a glass lens mold. To search for the amorphous alloys, Pt-Zr-Ni and Pt-Hf-Ni thin film libraries were fabricated using combinatorial arc plasma deposition (CAPD). The composition ranges of the amorphous region in each library were 50 to 60 at.% Pt, 0 to 20 at.% Ni, and balance being Zr or Hf. To evaluate the thermal and mechanical properties of these amorphous alloys, Pt51Zr39Ni10 and Pt52Hf36Ni12 samples, as typical amorphous samples, were prepared by sputtering. The Pt51Zr39Ni10 sample showed a crystallization temperature, Tx, of 939 K and a fracture stress, sf, of 1.44 GPa. The Pt52Hf36Ni12 sample showed a Tx of 978 K and a sf of 0.3 GPa. The Pt51Zr39Ni10 and Pt52Hf36Ni12 samples did not achieve the target Tx (973K) and sf (1.0 GPa). In order to achieve the target properties, Zr was displaced with Hf to increase the Tx of Pt-Zr-Ni and four Pt51HfxZr37-xNi12 samples were prepared. The Pt51Hf20Zr17Ni12 sample had a Tx of 992 K and a sf of 0.87 GPa, and almost achieved the target properties. The machinability of the Pt51Hf20Zr17Ni12 sample was also evaluated. Though this sample could be cut using a diamond tool, it did not show sufficient machinability. In order to improve the accuracy of the glass mold shape, the machinability of the Pt-based thin film amorphous alloys require further modification.