Фазовая диаграмма системы Fe-Ir

К оглавлению: Другие диаграммы (Others phase diargams)

Fe-Ir (Iron-Iridium) L.J. Swartzendruber The known equilibrium phases of the Fe-Ir system are (1) the liquid, L; (2) the bcc low-temperature (aFe) solid solution; (3) the bcc high temperature ( dFe) solid solution; (4) the fcc (gFe,Ir) continuous solid solution; and (5) the e phase, a cph structure that forms at lower temperatures near the center range of alloy compositions. The assessed phase diagram is only tentative. The L + (gFe,Ir) = (dFe) peritectic at 1546 C is based on the thermal analysis data of [63Buc], which were corrected to yield a melting point of 1538 C for pure Fe. The data were then fitted using thermodynamic modeling. The calculated diagram generally exhibits good agreement with experimental results in the Fe-rich portion where data are available. There appears to be a small systematic deviation in some of the L/(gFe,Ir) solidus data; hence, only the L/(gFe,Ir) liquidus data points were utilized to model the L/(gFe,Ir) boundaries. No data are available on the (aFe)/(gFe,Ir) equilibrium boundaries. Some of the dashed boundaries at lower temperatures were constructed using the (gFe,Ir) <259> (aFe) and (aFe) <259> (gFe,Ir) martensite and austenite transformation temperatures presented by [37Fal]. These measured transformation temperatures do not represent transitions through equilibrium phase boundaries. The proposed equilibrium lines were drawn using thermodynamic modeling. The e phase in the central region of the diagram was reported by [64Rau]. Because of the sluggishness of the transformation, the true location of the e/( gFe,Ir) boundaries is difficult to ascertain. The Curie temperature of the bcc phase decreases at a rate of about 4 C per atomic percent Ir from the value of 770 C for pure Fe, and the average magnetic moment rises slightly from the 2.2 Bohr magneton value for pure Fe, attaining a maximum of about 2.26 Bohr magnetons at 7 at.% Ir. As a dilute impurity in fcc Ir, Fe has only a very small magnetic moment. A peak in the magnetic susceptibility, characteristic of an antiferromagnetic-type order, exists near 50 K for fcc alloys with 60 and 70 at.% Ir. 37Fal: M. Fallot, Compt. Rend., 205, 517-518 (1937) in French. 63Buc: R.A. Buckley and W. Hume-Rothery, J. Iron Steel Inst., 121-124 (Feb 1963). 64Rau: E. Raub, O. Loebich, Jr., and H. Beeskow, Z. Metallkd., 55(7), 367-370 ( 1964). Published in Bull. Alloy Phase Diagrams, 5(1), Feb 1984. Complete evaluation contains 4 figures, 3 tables, and 14 references. 1