Experimental determination of the phase relations of the Co–Pt–Dy system at 773 K

Abstract

The isothermal section of the Co–Pt–Dy system at 773 K was experimentally determined by combining results from X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy investigations. The presence of Co3Dy4 phase at 773 K is confirmed in this study. The four-phase region does not exist at 773 K in the ternary Co–Pt–Dy system, with instead two three-phase regions consisting of Co, DyPt, Dy3Pt4 and Co, DyPt2, Dy3Pt4, respectively. 23 single-phase regions (including solid solution regions of the binary compounds) and 21 three-phase regions were identified to exist at this isothermal section. The highest solid solubility of Dy in α1(Co, Pt), ∊(Co, Pt), α2(Co, Pt), CoPt, CoPt, α(Pt, Co) is less than 1.5 at.% Dy and that of Co in Dy3Pt, Dy2Pt, Dy5Pt3, Dy5Pt4, DyPt, Dy3Pt4, DyPt3, DyPt5 is below 1 at.% Co. The DyPt2 phase dissolves up to about 19 at.% Co. The maximum solid solubility of Pt in Co2Dy, Co3Dy, Co7Dy2, Co17Dy2 is approximately 1 at.% Pt. No new binary and ternary phases were found.