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High-Resolution Electron Microscopy Study of Phase Transformations in Dental Alloys

牙科合金相变的高分辨率电子显微镜研究

基本信息

批准号：
63044111
负责人：
YASUDA Katsuhiro
金额：
$ 2.56万
依托单位：
Nagasaki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Overseas Scientific Research
财政年份：
1988
资助国家：
日本
起止时间：
1988 至无数据
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63044111/
关键词：
Phase Transformation Age-hardening Dental Gold Alloy X-ray Diffraction Electron Microscopy

项目摘要

The eventual purpose of the present research project was the tailoring of new type dental alloys based on designing principle which was constructed with elucidating the correlationship between mechanical, electrochemical, biological factors and microstructural features of the alloy crystal, because these factors were governed greatly by solid interface such as grain boundaries, stacking faults, twin boundaries, and antiphase domain boundaries. The followings were concrete descriptions of the research project. (1) Construction of the coherent phase diagram of AuCu-Ag and (Ag_<0.5> Cu_<0.5>)_x-Au_<1-x> sections combining a theoretical results and available experimental data. (2) High-resolution electron microscopic observations of the long period antiphase domain boundary structure in AuCu-Ag pseudobinary alloys. (3)Structural features of twin boundary in AuCu-3at. %Ag alloy. (4) High-resolution electron microscopic study of age-hardening mechanisms and the associated phade transformatio … More ns in commercial dental gold alloys. Works done were as follows: (1) Three distinguishable mode of phase transformations were found in the AuCu-Ag pseudobinary system, i.e., (i) the AuCu ordering was brought about solely from disordered solid solution of FCC in structure ( _0 phase) at a composition region of outside of the miscibility gap. It was found that a temperature region of coexistence of the _0 disordered and AuCu II ordered phases, a single phase region of AuCu II ordered phase, a region of coexistence of two ordered phases AuCu i and AuCu II, and a single phase region of AuCu I were formed in aucu-3at. %Ag alloy under the critical temperature for ordering at 653K, (ii) dual mechanism of ordering and two-phase decomposition was induced by ageing in a composition region between the miscibility gap and a spinodal lucus. The phase transformations were governed by a nucleation and growth process in this composition range, i.e., (a) a two-phase decomposition region containing copper-rich FCC _1 and silver-rich FCC _2 phases, (b) a coexisting region of two disordered phases and an ordered phase, _1+ _2+AuCu II, (c) a coexisting region of an ordered phase and a disordered phase, AuCu II + _2, (d) coexisting region of two ordered phases and a disordered phase, AuCu I + AuCu II + _2, and (e) a coexisting region of an ordered phase and a disordered phase, AuCu I + _2, and (iii) dual mechanism of ordering and the spinodal decomposition was generated by ageing in a composition region of inside of the spinodal lucus. A rate of the process of the phase transformation was higher in this composition range than in a composition range located between the miscibility gap and the spinodal lucus. Phases coexisting were essentially analogous to this range except for differences in microstructures.Although the differences in microstructures induced by ageing were the most inportant and great interest, the temperatures and composition dependence of the phase changes have not been determined exactly yet. (2) High-resoultion electron microscopic observations were performed to clarify a configuration of the long period antiphase domain boundary, structural characteristics of interfaces between different phases, and wtin boundary in AuCu-3at.%Ag, AuCu-6at.%Ag, AuC1-9at.% and AuCu-14at.%Ag alloys which were aged at various temperatures and periods. The microstructure induced by ageing was quite different from each other depending on silver content in the alloys, i.e., the AuCu ordering was brought about solely from disordered solid soulution in a composition range of outside of the miscibilith gap, the phase transformation was governed by a nucleation and growth mechanism in a composition range between the miscibility gap and a spinodal lucus and the AuCu ordering was concurrent with the spinodal decomposition in a composition range of inside of the spinodal lucus. The characteristic mosaic structure which cosisted of the AuCu II ordered phase and a silver-rich disordered FCC _2 phase was found in high-resolution electron micrographs obtained from the AuCu-9at.%Ag alloy aged at 614K for 100ks. (3) During the course of a systematic study to determine the coherent phase diagrams of Au-Cu-Ag ternary system, it was necessary to identify a disordered FCC phase coexisting with the AuCu II long period superstructure, as was expected from the phase rule. High-resolution electronmicroscopy was employed to distinct the disordered FCC phase and the AuCu II phase in th AuCu-3at.%Ag alloy aged at 643K for 100ks. It was found that a triangle shaped area was formed in the vicinity of the tip of the twin platelets. The triangle shaped area showed a considerable amount of ealstic strain and was thought to be the disordered FCC phase from geometric features of atomic configurations. (4) Age-hardening characteristics of a commercial dental gold alloy, Au-5wt.%Pt-3wt.%Pd-6wt.%Ag-15wt.%Cu-3wt.%Zn, were studied by means of resistometric measurements, hardness tests, X-ray diffraction and electron microscopy. At lower ageing temperatures the hardening was due to the nucleation of the AuCu I type ordered structure and was characterized by a slow growth rate of the ordered platelets. An alternating coarse AuCu I ordered platelets abutted on each other was formed by ageing at higher temperatures. No strain field was observed at the interfaces between the AuCu I ordered platelets and the surrounding matrix in this temperature range. Less

本研究的最终目的是在阐明力学、电化学、生物因素与合金晶体微观组织特征之间的关系的基础上，根据设计原理定制新型牙科合金，因为这些因素在很大程度上受晶界、层错、孪晶界和反相畴界等固体界面的制约。以下是对研究项目的具体描述。(1)结合理论结果和已有实验数据，构建了AuCu-Ag和（Ag_<0.5> Cu_<0.5>）_x-Au_<1-x>截面的相干相图。(2) AuCu-Ag伪二元合金长周期反相畴边界结构的高分辨率电镜观察。(3) AuCu-3at双晶界构造特征。% Ag)合金。(4)高分辨率电镜研究了商用牙用金合金的时效硬化机制和相关的相转变。所做的工作如下：(1)在AuCu- ag伪二元体系中发现了三种可区分的相变模式，即：(1)AuCu有序完全是由FCC结构（_0相）在混相间隙外组成区域的无序固溶体引起的。结果表明，在AuCu -3at中形成了_0无序相和AuCu II有序相共存的温度区、AuCu II有序相的单相区、AuCu i和AuCu II两种有序相共存的温度区和AuCu i单相区。%Ag合金在653K的有序临界温度下，（ii）在混相间隙和spinodal lucus之间的成分区域时效，诱导了有序和两相分解的双重机制。相位转换是由成核和生长过程组成范围内,也就是说,(a)两阶段分解区域包含铜FCC _1和蕴藏白银FCC _2阶段,(b)共存区域无序和有序阶段两个阶段,_1 + _2 + AuCu II, (c)有序相共存的地区和无序阶段,AuCu II + _2, (d)共存地区两个命令阶段和无序阶段,AuCu I + AuCu II + _2(e)有序相与无序相共存区AuCu I + _2；（iii）在spinodal lucus内部的组成区，老化产生了有序和spinodal分解的双重机制。在这一成分范围内，相变的速率高于位于混相间隙和旋多点之间的成分范围。除了微观结构不同之外，共存的相基本上与此范围相似。虽然老化引起的微观结构差异是最重要和最感兴趣的，但相变的温度和成分依赖尚未准确确定。(2)通过高分辨率电镜观察，明确了AuCu-3at长周期反相畴边界的构型、不同相界面的结构特征和wtin边界。% Ag, AuCu-6at。% Ag, AuC1-9at。%和AuCu-14at。经过不同温度和时间时效处理的%Ag合金。合金中银含量的不同，时效引起的微观组织也有很大差异，即AuCu有序完全是由混相间隙外组成范围内的无序固溶体引起的；相变在混相间隙和旋枝lucus之间的组成范围内受形核和生长机制支配，在旋枝lucus内部的组成范围内，AuCu有序与旋枝分解同时发生。在高分辨率电子显微图上发现了由AuCu-9at有序相和富银无序FCC 2相组成的特征性镶嵌结构。%Ag合金在614K时效100k。(3)在系统研究Au-Cu-Ag三元体系相图的过程中，有必要确定与AuCu II长周期上层结构共存的无序FCC相，正如相律所期望的那样。采用高分辨率电子显微镜对AuCu-3at中无序FCC相和AuCu II相进行了区分。%Ag合金在643K时效100k。结果发现，在双血小板尖端附近形成了一个三角形区域。三角形区域显示出相当大的实际应变，从原子构型的几何特征可以认为是无序的FCC相。(4)商用牙科用金合金Au-5wt.%Pt-3wt.%Pd-6wt.%Ag-15wt.%Cu-3wt的时效硬化特性。采用电阻测量、硬度测试、x射线衍射和电子显微镜等方法对其进行了研究。在较低的时效温度下，硬化是由于AuCu I型有序结构的成核，其特征是有序血小板的生长速度较慢。在较高的温度下老化形成了彼此相邻的交替粗糙的AuCu I有序血小板。在此温度范围内，在AuCu I有序血小板与周围基质之间的界面处未观察到应变场。少