Temperature dependence of thermal expansion coefficient for palladium-based binary alloy.

Temperature dependencies of thermal expansion coefficients for the alloys of Pd-Ag, Pd-Cu and Pd-Co binary systems were measured at temperatures up to 900 degrees C, with heating and cooling rates of 5 degrees C/min. The coefficient of thermal expansion of alloys with no transformation in the temperature range of interest in porcelain firing was well approximated by a linear equation of temperature. The constants in the equation were shown as a function of the weight for the added element. Thermal expansion of the palladium-based alloy with no transformation was well estimated at any temperature range and at any composition by using the constants represented here. The coefficients of thermal expansion before and after order-disorder transformation and magnetic transformation were measured in Pd-Cu and Pd-Co alloys, respectively. The results suggest that transient and residual stresses in porcelain-fused-to-metal restorations can be effectively controlled by making use of transformation of the alloy.