| Research Abstract |
In 1986, sixteen kinds of Au-Pt-Cu-Ag alloys (PTG), containing 70 part of Au+Pt, 30 part of Cu+Ag, 2 part of Zn as a deoxidizer and 0.05 part of Ir as a grain refiner were melted in pure argon atomosphere. Test specimens were made from these alloy ingots using dental precision casting, and the mecanical properties after quenching (softning) and hardening heat treatment were measured. After the hardening heat treatment, tensile strength, elongation, and Vickers hardness of 65Au-5Pt-20Cu-15Ag (PTG-3) and 60Au-10Pt-15Cu-15Ag (PTG-6) alloy were over 95kgf/mm^2, over 2% and over 300, respectively. These two alloys were most optimum among the 16 tested alloys. In addition to these tests, mechanical properties for twelve kinds of Ag-Pd-Cu ternary alloys (AP), containing 25-40wt% Pd, 15-25wt% Cu, were also mesured using the method described above. The 35Pd-20Cu-45Ag ternary alloy had maximum tensile strength after hardening heat treatment. A 10% Au was added to the alloys close to this composi
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tion and their mechanical properties were also measured. 10Au-30Pd-20Cu-40Ag (APG-7) and 10Au-30Pd-25Cu-35Ag (APG-11) were suitable for adhesion bridges from the view of their tensile strength and Vicker's hardness that were 101kgf/mm^2, 343 and 104kgf/mm^2, 358, respectively.
In 1987, a method for bond strength was newly developed using two small test pieces(10 , 6h). This method enabled to measure four types of bond strength(sher bond strength by compression loading,tensile bond strength, bending bond strength and torsional shear bond strength). The shear bond strength by compression loading and tensile bond strength were measured for the aforementioned 4 alloys (PTG-3, PTG-6, APG-7, APG-11) with 4META system adhesives (Superbond C&B, SB C&B) and phosphoric ester system adhesives (Panavia EX, PEX). When PEX was used, for all types of alloys, the bond strength on the polished surface was small, however, the bond strength of 400-500kgf/cm^2 was shown on the oxidized surface that was created by the hardening heat tereatment, and on the tin-plated surface. When SB C＆B was used, every alloys adhered well with all surfaces, polished, oxidized, and tin-plated surfaces, and their bond strength were over 400kgf/cm^2. It is concluded that if appropriate surface treatment is carried out on precious alloys such as platinum added gold alloys (PTG) and gold-silver-palladium alloys (APG), the shear bond strength by compression loading and tensile bond strength are more than 600kgf/cm^2. Less
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