An investigation of phase separation in the Ir-Pt binary system

Yoko Yamabe-Mitarai, Takeshi Aoyagi, Taichi Abe

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


In the past two different phase diagrams of the Ir-Pt system have been proposed, where the miscibility gap in the fcc solid solution exhibits a different peak temperature and composition. In the present work, to examine the miscibility gap in the Ir-Pt system, the metallurgical microstructure was observed using scanning electron microscopy (SEM) equipped electron probe X-ray microanalyzer (EPMA). The phase identification and lattice parameter change were obtained from X-ray diffractometry (XRD) for the Ir-25, 35, 50, and 75 at.%Pt alloys at temperatures from 1123 K to 1573 K. The results show that the heat treatment of this alloy should be better than 1973 K/72 h, in order to homogenize the specimens that exhibit the usual dendrite structure, as found in as-cast specimens. Although ab initio calculations predict the existence of the miscibility gap, the estimated peak temperature of the two-phase boundary, 1000 K, is too low to obtain the two-phase structure from experiments. This is the reason there is no indication of the two-phase structure in the present work and the two-phase boundaries reported previously may be due to insufficient homogenization.

Original languageEnglish
Pages (from-to)327-334
Number of pages8
JournalJournal of Alloys and Compounds
Issue number1-2
Publication statusPublished - 2009 Sep 18
Externally publishedYes


  • High temperature materials
  • Phase diagrams
  • Scanning electron microscopy
  • X-ray diffraction

ASJC Scopus subject areas

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


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