Lee Hee-Kyung, Moon Hi-Man, Seol Hyo-Joung, Lee Jung-Eun, Kim Hyung-Il
Department of Dental Materials, College of Dentistry, Pusan National University, 1-10 Ami-dong, Seo-gu, Pusan 602-739, South Korea.
Biomaterials. 2004 Aug;25(17):3869-75. doi: 10.1016/j.biomaterials.2003.10.037.
Commercial low-gold dental casting alloy composed of Ag-Pd-In-Au-Zn was studied to clarify the age-hardening mechanism and related microstructural changes. The hardness of solution-treated specimen began to increase and reached the maximum value with ageing time, and then the maximum hardness value decreased by further ageing. The changes of X-ray diffraction (XRD) pattern during isothermal ageing revealed that the age hardening was not caused by phase transformation. By comparing the age-hardening curve with the changes in full-width at half-maximum of the XRD peaks at each ageing time, it was revealed that the coherency strains were formed in the Ag-rich matrix, which contributed to the hardness increase during ageing. From scanning electron microscopic observation and electron probe microanalysis, it was clarified that fine particle-like structures composed of InPd containing small amount of Zn gathered by diffusion in the Ag-rich matrix, and the coherency strains which formed during that time caused the hardness increase in the early stage of age-hardening process. The coherency strains were released by the progress of coarsening of Zn-containing InPd dendrite during further ageing, which caused the overaging in the later stage of age-hardening process.
对由银-钯-铟-金-锌组成的商用低金牙科铸造合金进行了研究，以阐明时效硬化机制及相关的微观结构变化。固溶处理试样的硬度开始随时效时间增加，并达到最大值，然后进一步时效时最大硬度值下降。等温时效过程中X射线衍射（XRD）图谱的变化表明，时效硬化不是由相变引起的。通过将时效硬化曲线与每个时效时间的XRD峰半高宽变化进行比较，发现富银基体中形成了共格应变，这导致时效过程中硬度增加。通过扫描电子显微镜观察和电子探针微分析，明确了由含少量锌的铟钯组成的细颗粒状结构在富银基体中通过扩散聚集，在此期间形成的共格应变导致时效硬化过程早期硬度增加。在进一步时效过程中，含锌铟钯枝晶粗化的进程释放了共格应变，这导致时效硬化过程后期出现过时效。
