Comparative corrosion behavior of Au50-Ag25-Pd25 and Ni88.6-Cr11.4 alloys utilized in dental applications

The electrochemical behaviour of alloys (Au50-Ag25-Pd25 and Ni88.6-Cr11.4) was studied in Fusayama's artificial saliva at pH 6.5 and 37 °C by using open circuit potential, electro­chemical impedance spectroscopy, and potentiodynamic polarization measure­ments. Electrochemical impedance spectroscopy results were simulated with an equivalent electrical circuit. After immersion in artificial saliva, surface characterization of samples was done using scanning electron microscopy connected with energy-dispersive spectro­scopy. All obtained results revealed that Au50-Ag25-Pd25 alloy is much more resistive than Ni88.6-Cr11.4 and can be recommended for the effective treatment of patients with dental prosthetics that have metal frameworks. s

Atomic Ordering Behavior of CoTi Alloy with Addition of Transition Metals

The statistical-thermodynamic theory of ordering and electronic theory of ordering in the pseudo-potential approximation was used to study the influence of ternary addition of some transition metals on the atomic ordering behavior of Co0.5(Ti1-xMx)0.5 alloys with M = Fe, Pt, re, V, Cr, Mn, Ni, Cu, Zn, Zr, Ag, Hf or Au up to a concentration of 1 at.%. The partial ordering energies, order-disorder phase transformation temperatures and partial short range order parameters have been calculated for these alloys. The analysis shows that the impurity elements in Co0.5(Ti1-xMx)0.5 alloys can be divided into two main groups on the basis of lattice site occupancy i.e. M = V, Cr, Mn, Cu, Zn, Zr, Ag, Hf and Au mainly substitute for Co sublattice sites whereas M = Fe, Ni, Pt or re mainly substitute for Ti sublattice sites. Further, the order-disorder transformation temperatures were found to either increase or remain nearly unchanged by the addition of ternary impurities in the CoTi alloy depending on the absolute value of the partial ordering energies. Alloys of Ti with V, Cr, mn, Cu, Zn, Zr, Ag, Hf or Au in place of Co and alloys of Co with Fe, Ni, Pt or Re in place of Ti can be predicted for future. The results of the present analysis are in good agreement with the available experimental data on these alloys