INCREASEING THE TENSILE AND FATIGU STRENGTH MECHANISM OF DENTAL ALLOY

工业上可获得的12%Au-20%Pd-Ag-Cu合金已标准化为12wt%Au和20wt%Pd，其中Ag和Cu的含量分别为45-55wt%和15-20wt%。通过将该合金中的铜含量增加到三元合金相图中所示的共晶成分的极限，就有可能降低液相线。此外，共晶相中的a1和a2相的晶化比变大，与a1固溶体附近的成分相比，韧性有普遍的提高。本研究制作了一种实验合金，其中工业12wt%Au-Pd-Ag合金中的铜含量增加到25wt%，并研究了热处理与该合金拉伸性能的关系。作为进一步的研究，添加2wt%的锌对合金的力学性能有什么影响。本研究的结果表明：1)通过在三元相图的共晶线上寻找12wt%Au-20wt%Pd-Ag-Cu合金中的铜的含量，可以给时效区域和固溶硬化区赋予韧性。实验合金(标准合金)的延伸率比S-12锻造材料的延伸率提高了15%~22%。2)在905.6ﾟC下，标准合金的液相线温度低于S-12的945.5ﾟC和Castwell MC的915.9ﾟC，添加锌的合金的液相线温度为907.3ﾟ。然而，当这种合金在炉外进行风冷处理时，它的一些抗拉强度会被牺牲，但它的韧性会增加，伸长率也会增加。

Commercially available 12% Au-20% Pd-Ag-Cu alloys have been standardized at 12wt% Au and 20wt%Pd with the content of Ag and Cu varying from 45-55wt% and 15-20wt% respectively. By increasing the amount of Cu in this alloy to the limit of the eutectic composition shown in the ternary alloy phase diagram it is possible to lower the liquidus line. Moreone, the crystallization ratio of phase a1 and a2 of the eutectic phase becomes larger and, compared with the composition near the a1 solid-solution phase, a general enhancement of toughness can be anticipated.An experimental alloy was made for this study in which the amount of Cu in the commercial 12wt% Au-Pd-Ag alloy was increased to 25wt% and a study was made of the relationship between the heat treatment and the tensile characteristics of this experimental alloy. As a further study, 2wt% of Zn was added to this experimental alloy to see what effect shis might have on the mechanical properties.The re results of this study indicates :1) I am possible to give toughness to the aged area and solid-solution hardening area by seeking the amount if Cu in a 12wt%Au-20wt%Pd-Ag-Cu alloy on the eutectic line of a ternary phase diagram. The experimental alloy (standard alloy) had a improved elongation by from 15% to 22% compared with that of S-12 wrought material.2) At 905.6ﾟC,the liquidus phase temperature of standard alloy was lower than that of 945.5ﾟC for S-12 and 915.9ﾟC for Castwell MC.Also, the liquidus phase temperature for Zn added alloy was 907.3ﾟC.3) An addition of 2wt%Zn to the experimental alloy used in this experiment caused embrittlement. However, when this alloy is given air-cooled treatment outside the furnace, some of it's tensile strength is sacrificed but it's toughness increases and an elongation.