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영어

The physical property and phase transformation in a commercial dental casting high gold alloy was investigated as a function of ageing temperature and time usingmicrovickers hardness tester, X-ray diffraction, optical and electron microscopy andEPMA analyser. 1. With increasing ageing time, the hardness of solution-treated gold alloys increasedslowly at the initial stage of ageing treatment at an ageing temperature of 300~400℃,and it reached a maximum value of hardness at the medium stage. Finally, it decreasedgradually during further ageing. The maximum value of hardness at was similar with thatof the conventional materials and suitable for using as the crown & bridge. 2. During isothermal ageing at a temperature range of 300~400℃, three phasesconsisting of the Au-rich α₁phase with a face-centered cubic structure, the Pt3Zn α₂phasewith an ordered AuCu3(L12) type(f.c.c.) and the Pt-rich α₃phase with face-centered cubicstructure in solution-treated gold alloys were transformed into different three phasesconsisting of the α₁phase, the α₃phase and the PtZn βphase with an ordered AuCu I(L10)type. 3. The hardening of gold alloys was attributed to the lattice strains of the matrixresulting from the transformation of the α₂phase to the βphase.4. The softening of gold alloys during over-ageing was attributed to the coarsening ofthe nodules consisting of the βphase and α₁matrix.