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The objective of this research was to investigate the effect of constitutional phases on the unique hardening behavior of as-solutionized dental Ag–Pd–Au–Cu alloy fabricated by cold rolling. The commercial dental Ag–Pd–Au–Cu alloy fabricated by cold rolling consists of Cu-rich α1, Ag-rich α2, and β phases. On the other hand, the Ag–Pd–Au–Cu alloy fabricated by the liquid rapid solidification (LRS) method consists of single α phase. They were subjected to various heat treatments, respectively. The microstructures were observed by scanning electron microscope, transmission electron microscope and X-ray diffraction. The hardness was evaluated by a Vickers micro-hardness tester. In the Ag–Pd–Au–Cu alloy fabricated by cold rolling, the fine L10-type-ordered β′ phase is precipitated and the coarse β phase is remained after solution treatment at 1123 K. The hardness increases drastically. On the other hand, in the Ag–Pd–Au–Cu alloy fabricated by LRS method, the single α phase was decomposed into the α1 phase and the α2 phase after solution treatment at 1023 K and its hardness change was small. However, after aging treatment at 673 K, the fine β phase is precipitated in the α phase and the hardness increases greatly even in the Ag–Pd–Au–Cu alloy fabricated by LRS method. It is considered that the precipitation of the fine L10-type-ordered β′ phase may contribute strongly to the unique hardening in the as-solutionized dental Ag–Pd–Au–Cu alloy fabricated by cold rolling. |
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