ИСТИНА

Palladium-based alloys have been successfully applied in dentistry for a long. Gold, copper and tin are one of the most often used components of such alloys, their additions improve physical, mechanical and technological properties of the alloys in question. Alloy properties are strongly dependent on phase composition. In literature there are only scarce investigations of interactions between Pd, Cu, Au and Sn, mainly concerned mechanical and electrochemical properties, like [1]. No data on phase relations in quaternary Pd-Au-Cu-Sn system are given. So, the aim of the study was to investigate palladium corner of this quaternary system. Seven as-cast alloys of Pd-Au-Cu-Sn system were investigated. The alloy compositions were chosen in such a way that atomic ratio of FCC-components was constant and corresponded to that of commercial “Palladent” dental alloy (Pd:Au:Cu=11.1:1:4.6) [1]. As for tin concentration, it increased from 0 to 20 atomic percent. EDMA & X-ray diffraction analysis showed that up to 7.5 at.% Sn Pd-based FCC-solid solution exists. When further increasing tin content, second phase appears, similar to that has been detected in Pd-Au-Sn and Pd-Cu-Sn systems [2, 3]. This phase is a ternary τ1-phase, having body-centered tetragonal unit cell (I4/mmm space group) [2]. Microhardness tests showed that τ1 phase is harder than FCC solid solution. Increase in tin content makes hardness of both phases rise. These seven alloys were also investigated by EDMA after their annealing at 500 °C for 1100h. The results obtained were quite similar to that of as-cast alloys and were the basis for building palladium corner of the Pd-Au-Cu-Sn system at 500 °C.