Experimental and theoretical study of the phase equilibria in the fe-ni-w system
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I.
INTRODUCTION
A. Review of Previous Work
THE phase
equilibria in the Fe-Ni-W system have been studied experimentally several times, 1-4 starting with the work by Winkler and Vogel ~in 1932. The experimental data were first compiled by Winslow s and, more recently, by Raynor and Rivlin. 6'7 Winkler and Vogel 1 established the main features of the Fe-Ni-W phase diagram from a thermal and microscopical study of alloys of various Fe to Ni ratios and up to 45 pct W. Their results were presented in eight temperaturecomposition diagrams and a projection of the liquidus surface. Agababova and Chaporova2 studied the solubility of W in the ternary fcc phase by X-ray and microscopical analysis of sintered alloys of six Fe to Ni ratios and up to 40 pct W. Their measurements were performed at 1073, 1423, 1523, and 1623 K. By combining Winkler and Vogel's, 1 Agababova and Chaporova's, 2 and more recent 8'9'1° information on the binary systems Fe-Ni, Fe-W, and Ni-W, Winslow 5proposed a phase diagram for the Fe-Ni-W system. He constructed 10 isothermal sections for temperatures between 1073 and 1923 K by accepting the binary data and drawing the boundaries through ternary data points. In his evaluation he gave the highest weight to the points extracted from the paper by Winkler and Vogel. ~ Additional experimental data on the Fe-Ni-W phase diagram was provided later on by Bannykh et al. 3 and by Hofmann. 4 Bannykh et al. studied the system at 1073, 1473, and 1573 K. Their study involved the microscopical and X-ray examination of alloys with up to 20 pct Ni and up to 50 pct W. A comparison of their suggested phase diagram with Winslow's can be made only at 1073 K because Winslow did not present sections at the other temperatures. The most important difference between the isothermal sections at 1073 K is the presence of FEW2, a Laves phase, which was included by Winslow in his assessment but not detected by Bannykh et al. The other intermetallic phase stable in the Fe-W side of the diagram, proposed by Winslow, a /z-phase, was detected by Bannykh et al. and described in their diagram as a binary, stoichiometric phase with the composition FeTW6. A. FERN,~NDEZ GUILLERMET is with the Division of Physical Metallurgy, Royal Institute of Technology, S-10044 Stockholm, Sweden. L. OSTLUND, formerly with the Division of Physical Metallurgy, Royal Institute of Techno!ogy, is with Brukens H~irdverkst~ider, AB, Grossistv~igen 7, S-12530 Alvsj~5, Sweden. Manuscript submitted October 10, 1985. METALLURGICALTRANSACTIONSA
In the work by Hofmann, which is the more recent one, differential thermal analysis (D.T.A.), X-ray, dilatometry, optical metallography, and electron microprobe analysis were used to get information on the Fe-Ni-W phase diagram and on the binaries Fe-W and Ni-W. His suggested ternary diagram was presented in eight isothermal sections between 1273 and 1723 K, the solubility of W in fcc phase at 1123 K, temperature-composition sections corresponding to 5 pct, 15 pct, and 25 pct Ni, 75 pct W, of an Fe to Ni ratio of 5 : 5 and
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