Section of Oral Biology, The Ohio State University, Columbus, OH, USA.
J Mater Sci Mater Med. 2010 Oct;21(10):2723-31. doi: 10.1007/s10856-010-4116-3. Epub 2010 Jul 10.
The goals of this study were to investigate the fatigue limits of two Pd-Ag alloys (Ivoclar Vivadent) with differing mechanical properties and varying proportions of secondary alloying elements, examine the effect of casting porosity on fatigue behavior, and determine the effect of casting size on microstructures and Vickers hardness. The alloys selected were: IPS d.SIGN 59 (59.2Pd-27.9Ag-8.2Sn-2.7In-1.3Zn); and IS 64 (59.9Pd-26.0Ag-7.0Sn-2.8Au-1.8 Ga-1.5In-1.0Pt). Tension test bars, heat-treated to simulate dental porcelain application, were subjected to cyclic loading at 10 Hz, with R-ratio of -1 for amplitudes of compressive and tensile stress. Two replicate specimens were tested at each stress amplitude. Fracture surfaces were examined with a scanning electron microscope (SEM). Sectioned fatigue specimens and additional cast specimens simulating copings for a maxillary central incisor restoration were also examined with the SEM, and Vickers hardness was measured using 1 kg load. Casting porosity was evaluated in sectioned fatigue fracture specimens, using an image analysis program. The fatigue limit (2 × 10(6) loading cycles) of IS 64 was approximately 0.20 of its 0.2% yield strength, while the fatigue limit of d.SIGN 59 was approximately 0.25 of its 0.2% yield strength. These relatively low ratios of fatigue limit to 0.2% yield strength are similar to those found previously for high-palladium dental alloys, and are attributed to their complex microstructures and casting porosity. Complex fatigue fracture surfaces with striations were observed for both alloys. Substantial further decrease in the number of cycles for fatigue failure only occurred when the pore size and volume percentage became excessive. While the heat-treated alloys had equiaxed grains with precipitates, the microstructural homogenization resulting from simulated porcelain firing differed considerably for the coping and fatigue test specimens; the latter specimens had significantly higher values of Vickers hardness.
本研究的目的是探讨两种具有不同力学性能和不同次生合金元素比例的 Pd-Ag 合金（义获嘉维他）的疲劳极限，研究铸造孔隙度对疲劳行为的影响，并确定铸造尺寸对微观结构和维氏硬度的影响。选择的合金为：IPS d.SIGN 59（59.2Pd-27.9Ag-8.2Sn-2.7In-1.3Zn）和 IS 64（59.9Pd-26.0Ag-7.0Sn-2.8Au-1.8Ga-1.5In-1.0Pt）。经模拟牙瓷应用热处理的拉伸试验棒在 10Hz 下进行循环加载，压缩和拉伸应力的 R 比为-1，幅度为。每种应力幅度测试两个重复样本。用扫描电子显微镜（SEM）检查断裂面。还使用 SEM 检查了模拟上颌中切牙修复的牙冠的节段疲劳试样和额外铸造试样，并使用 1kg 载荷测量维氏硬度。使用图像分析程序评估节段疲劳断裂试样中的铸造孔隙度。IS 64 的疲劳极限（2×10(6)次加载循环）约为其 0.2%屈服强度的 0.20，而 d.SIGN 59 的疲劳极限约为其 0.2%屈服强度的 0.25。这些疲劳极限与 0.2%屈服强度的相对较低比值与先前发现的高钯牙科合金相似，这归因于它们的复杂微观结构和铸造孔隙度。两种合金均观察到具有条纹的复杂疲劳断裂表面。只有当孔径和体积百分比过大时，疲劳失效的循环次数才会大幅减少。虽然热处理合金具有等轴晶粒和析出物，但模拟瓷化烧制导致的微观结构均匀化对牙冠和疲劳试验试样有很大差异；后者试样的维氏硬度值显著更高。
