Mechanism of unique hardening of dental Ag-Pd-Au-Cu alloys in relation with constitutional phases

Yonghwan Kim, Mitsuo Niinomi, Masaaki Nakai, Toshikazu Akahori, Toru Kanno, Hisao Fukui

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

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 α 1, Ag-rich α 2, 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 L1 0-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 α 1 phase and the α 2 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 L1 0-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.

Original languageEnglish
Pages (from-to)15-24
Number of pages10
JournalJournal of Alloys and Compounds
Volume519
DOIs
Publication statusPublished - 2012 Apr 5

Keywords

  • Ag-Pd-Au-Cu alloy
  • Liquid rapid solidification method
  • Microstructural change
  • Unique hardening behavior

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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