Development of microstracture on increasing fatigue toughness of dental Ag-Pd-Cu-Au alloy

对热处理后的牙科用Ag-Pd-Cu-Au合金在空气中进行了疲劳试验。研究了显微组织对疲劳特性的影响。在水淬态合金中，疲劳强度提高了低周疲劳区域的固溶温度。时效合金中，低周疲劳区B相的析出强化导致疲劳强度提高，而高周疲劳区B相析出导致疲劳强度显著降低。在时效条件下，当析出B相的体积分数不变时，随着析出B相直径的增大，Ag-Pd-Cu-Au合金的断裂次数增加。断裂韧性随试件侧面滑移区宽度的增加而增大。断裂韧性随裂纹偏转程度的增加而增加，Al相体积分数较大的合金由于高周疲劳区A1相的加工硬化而具有优异的疲劳强度。但为了提高疲劳强度的绝对值，应考虑B相的体积分数。

A fatigue test was carried out on heat-treated dental Ag-Pd-Cu-Au alloys in air. The effect of microstracture on fatigue characteristics was investigated. In the water quenched alloys, the fatigue strength increasing solutionizing temperature in the low-cycle fatigue region. While the fatigue strength decreased with increasing solutionizing temperature in the high-cycle fatigue region.In aged alloys, the fatigue strength increased due to precipitation strengthening caused by the precipitation of B phase in the low-cycle fatigue region, while the fatigue strength markedly decreased due to the precipitated B phase, which let to a fracture site in the high-cycle fatigue regions.The fracture touness of Ag-Pd-Cu-Au alloy increased with the increasing diameter of precipitated B phase in under aged conditions when volume fraction of precipitated B phase is constant. The fracture toughness increases with increasing width of slip area observed on the side surface of the specimen. The fracture toughness increased with the degree of crack deflection.The fatigue strength of alloy with a large volume fraction of al phase was excellent due to the work hardening of a1 phase in the high-cycle fatigue region. However, the volume fraction of the B phase should be taken into account in order to improve the absolute value of fatigue strength.