Ohno H, Miyakawa O, Watanabe K, Siokawa N
Shika Rikogaku Zasshi. 1978 Apr;19(46):112-25.
One hundred and thirty-nine tensile-test specimens of Au-Pd-Ag-Cu alloy were cast in various casting conditions. The specimens were subjected age-hardening heat-treatment. The casting porosities and the nonmetallic inclusions in the surface of a tensile-test fracture of cast specimens were observed and analyzed by use of Electron Probe X-ray Microanalyzer (EPMA). The polosity ratio that is the area ratio of the porosities to the fracture surface was determined. Studies were quantitatively made on the effect of the porosity ratio on the tensile strength and the elongation. Furthermore, the effect of the casting conditions on the tensile strength was investigated. The main results were summarized as follows; The tensile strength decreased only slightly within about 15% of the porosity ratio and remarkably with an increase in its ratio in the range from about 15% to 50%. The elongation, however, decreased considerably in the presence of the porosities of only a few per cent. Aspects of the decrease curves on the tensile strength and the elongation were represented in the shape of an inverse S-type and hyperbolic curve with an increase in the porosity ratio, respectively. With an increase in the porosity ratio, the shapes of the tensile-test specimens at the fracture part and load-elongation curves in the tensile-tests were shown as a brittle fracture. However, the result observed by a scanning electron microscope revealed that the fracture surfaces without the porosities showed mostly "dimple pattern" suggesting a characteristic figure of a ductile fracture. The nonmetallic inclusions in the fracture surfaces were identified as SiO2 (quartz) which was derived from an ingredient of an investment by comparing the inclusion with the reference standards on the characteristic X-ray O Kalpha spectra by EPMA. The microstructures observed by a light microscope showed a coarse structure with the high temperature casting conditions. However, the results of a scanning electronmicroscopy revealed that the microstructres observed in high magnifications of about 1000 to 3000 composed of two structures; micro-lamella and Widmanstätten structure, and no difference was shown in the various casting conditions. Therefore, it is concluded in the present alloy that a coarseness of the microstructures observed by a light microscope become no reason for a decrease of the tensile strength.
在不同铸造条件下铸造了139个Au-Pd-Ag-Cu合金拉伸试验试样。对试样进行时效硬化热处理。利用电子探针X射线微分析仪（EPMA）观察和分析铸造试样拉伸试验断口表面的铸造孔隙率和非金属夹杂物。测定了孔隙率与断口表面的面积比即孔隙率比。定量研究了孔隙率比对拉伸强度和伸长率的影响。此外，还研究了铸造条件对拉伸强度的影响。主要结果总结如下：在孔隙率比约15%以内，拉伸强度仅略有下降，而在约15%至50%的范围内，随着孔隙率比的增加，拉伸强度显著下降。然而，即使孔隙率仅为百分之几，伸长率也会大幅下降。随着孔隙率比的增加，拉伸强度和伸长率的下降曲线分别呈现反S型和双曲线形状。随着孔隙率比的增加，拉伸试验试样断口部分的形状和拉伸试验中的载荷-伸长曲线显示为脆性断裂。然而，扫描电子显微镜观察结果表明，无孔隙的断口表面大多呈现“韧窝花样”，表明是韧性断裂的特征形貌。通过EPMA对断口表面的特征X射线O Kα光谱与参考标准进行比较，确定断口表面的非金属夹杂物为源自铸型成分的SiO₂（石英）。光学显微镜观察到的微观结构在高温铸造条件下呈现出粗大的结构。然而，扫描电子显微镜结果显示，在约1000至3000的高放大倍数下观察到的微观结构由两种结构组成：微片层和魏氏组织，且在不同铸造条件下未显示出差异。因此，在本合金中得出结论，光学显微镜观察到的微观结构粗大并非拉伸强度降低的原因。
