Fundamental study high strength Au-Pd-Cu alloys

本研究的目的是为高强度牙科金合金的开发提供基础数据。在氩气气氛中，采用感应熔炼法制备了20种含10、20、30、40和50质量% Pd，10、20、30和40质量% Cu和10-80质量% Au的Au-Pd-Cu合金，测定了合金的熔点、维氏硬度、抗变色性和比重，并采用X射线衍射法测定了合金的物相。结果表明：1）实验合金的液相线温度在1035 ~ 1388 ℃之间，且随着Cu含量的降低和Pd含量的增加而升高。从实际应用的角度来看，应通过添加其他金属元素来降低液相线温度。2）含20-30质量% Cu的实验合金在失泽试验后显示出最高的亮度（L^*）。试验前后的白度差（Δ L ^*）随着Cu含量的增加而增加。另一方面，铸态、淬火和热硬化合金的L^*=70，显示出良好的抗失泽性。3）铸态合金的维氏硬度值范围为63.2-319，淬火合金的维氏硬度值范围为74.4-197，热硬化合金的维氏硬度值范围为74.5-291。假设抗拉强度为Hv数的1/3，则具有高Hv的实验合金的抗拉强度可能超过95 kgf/mm^2。从这个结果来看，高强度合金的成分估计为50- 70 Au-20- 30 Cu-10- 30 Pd。4）比重测量结果表明，含50mass%Pd或10mass%Cu的合金都能产生较多的气孔。5）X-射线衍射分析表明，合金的相组成为Au-20 - 30 Cu-10 - 30 Pd。X射线衍射分析表明，合金的硬化是基于AuCu和PdCu超晶格的形成。

The purpose of this study was to obtain fundamental data for the development of high strength dental gold alloys. Twenty Au-Pd-Cu alloys containing 10,20,30,40 and 50 mass% Pd, 10,20,30 and 40 mass% Cu and 10-80 mass% Au were made using induction melting in argon gas atmosphere, Melting point, Vickers hardness, tarnish resistance, and specific gravity were measured, and the phases of the alloys were determined using X-ray diffraction. The following summary is drawn.1) The liquidus point of experimental alloys ranged from 1035ﾟC to 1388ﾟC,and increased with the decrease of Cu content and the increase of Pd content. For the practical use, this result indicates that the liquidus point should be lowered by adding the other metal elements.2) The experimental alloys containing 20-30 mass% Cu showed the highest brightness (L^*) after the tarnish test. The defference in the brightness (DELTAL^*) before and after the test increased with the increase of the Cu content. On the other hand, the as cast, quenched and heat-hardened alloys had L^*=70, showing good tarnish resistance.3) Vickers hardness number ranged from 63.2-319 for the as cast alloys, 74.4-197 for the quenched alloys and 74.5-291 for the heat-hardened alloys. Assuming that the tensile strength is 1/3 of Hv number, experimental alloys with high Hv may have more than 95kgf/mm^2 tensile strength. From this result, the composition of high strength alloys is estimated to be 50-70Au-20-30Cu-10-30Pd.4) The result of specific gravity measurement suggests that more blow holes can be produced in the alloys containing either 50 mass% Pd or 10mass% Cu.5) The alloy phase analysis using X-ray diffraction indicates that the hardening of the alloys is based on the formation of AuCu and PdCu superlattice.