The Dy-Zn phase diagram

The dysprosium-zinc phase diagram has been investigated over its entire composition range by using differential thermal analysis, (DTA) metallographic analysis, X-ray powder diffraction, and electron probe microanalysis (EPMA). Seven intermetallic phases have been found and their structures confirmed. DyZn, DyZn₂, Dy₁₃Zn₅₈, and Dy₂Zn₁₇ melt congruently at 1095 °C, 1050 °C, 930 °C, and 930 °C, respectively. DyZn₃, Dy₃Zn₁₁, and DyZn₁₂ form through peritectic reactions at 895 °C, about 900 °C and 685 °C, respectively. Four eutectic reactions occur at 850 °C and 30.0 at pct Zn (between (Dy) and DyZn), 990 °C and 60.0 at pct Zn (between DyZn and DyZn₂), 885 °C and 76.0 at pct Zn (between DyZn₃ and Dy₃Zn₁₁), and 875 °C and 85.0 at pct Zn (involving Dy₁₃Zn₅₈ and Dy₂Zn₁₇). The Dy-rich end presents a catatectic equilibrium; a degenerate invariant effect has been found in the Zn-rich region. The phase equilibria of the Dy-Zn alloys are discussed and compared with those of the other known RE-Zn systems (RE=rare earth metal) in view of the regular change in the relative stabilities of the phases across the lanthanide series     

The neodymium-gold phase diagram

The Nd-Au phase diagram was studied in the 0 to 100 at. pct Au composition range by differential thermal analysis (DTA), X-ray diffraction (XRD), optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Six intermetallic phases were identified, the crystallographic structures were determined or confirmed, and the melting behavior was determined, as follows: Nd₂Au, orthorhombic oP12-Co₂Si type, peritectic decomposition at 810 °C; NdAu, R.T. form, orthorhombic oP8-FeB type, H.T. forms, orthorhombic oC8-CrB type and, at a higher temperature, cubic cP2-CsCl type, melting point 1470 °C; Nd₃Au₄, trigonal hR42-Pu₃Pd₄ type, peritectic decomposition at 1250 °C; Nd₁₇Au₃₆, tetragonal tP106-Nd₁₇Au₃₆ type, melting point 1170 °C; Nd₁₄Au₅₁, hexagonal hP65-Gd₁₄Ag₅₁ type, melting point 1210 °C; and NdAu₆, monoclinic mC28-PrAu₆ type, peritectic decomposition at 875 °C. Four eutectic reactions were found, respectively, at 19.0 at. pct Au and 655 °C, at 63.0 at. pct Au and 1080 °C, at 72.0 at. pct Au and 1050 °C, and, finally, at 91.0 at. pct Au and 795 °C. A catatectic decomposition of the (βNd) phase, at 825 °C and ≈1 at. pct Au, was also found. The results are briefly discussed and compared to those for the other rare earth-gold (R-Au) systems. A short discussion of the general alloying behavior of the “coinage metals” (Cu, Ag, and Au) with the rare-earth metals is finally presented.     

The coherent phase diagram of Cu-Ni-Zn

The phase diagram for the f.c.c. part of the CuNiZn system has been derived using the tetrahedron approximation of the Cluster Variation Method. The pair-wise interaction potentials have been obtained from a pseudopotential model for the stoichiometric Cu₂NiZn composition. The results obtained are combined with the cluster variation method in order to make predictions on the phase diagram of the CuNiZn system. In particular, this paper reports the influences which the various more-body forces exert on the shape of the regions in the phase diagram where ordering occurs. The predictions on the phase diagram of the ternary system CuNiZn are in reasonable agreement with experiments and are the least topologically correct.     

The ternary phase diagram,Fe-Ni-P

In order to provide the necessary phase equilibria data for understanding the development of the Widmanstatten pattern in iron meteorites, we have redetermined the Fe-Ni-P phase diagram from 0 to 100 pct Ni, 0 to 16.5 wt pct P, in the temperature range 1100° to 550°C. Long term heat treatments and 130 selected alloys were used. The electron microprobe was employed to measure the composition of the coexisting phases directly. We found that the fourphase reaction isotherm, where α+ liq ⇌ γ+ Ph, occurs at 1000° ± 5°C. Above this temperature the ternary fields α+ Ph + liq and α+ γ+ liq are stable and below 1000°C, the ternary fields ⇌+ γ + Ph and γ + Ph + liq are stable. Below 875°C a eutectic reaction, liq → γ + Ph, occurs at the Ni-P edge of the diagram. Altogether nineteen isotherms were determined in this study. The phase boundary compositions of the two-and three-phase fields are listed and are compared with the three binary diagrams. The α + γ + Ph field expands in area in each isotherm as the temperature decreases from 1000°C. Below 800°C the nickel content in all three phases increases with decreasing temperature. The phosphorus solubility in α and γ decreases from 2.7 and 1.4 wt pct at 1000°C to 0.25 and 0.08 wt pct at 550°C. The addition of phosphorus to binary Fe-Ni greatly affects the α/α + γ and γ/α + γ boundaries below 900°C. It stabilizes the α phase by increasing the solubility of nickel (α/α +γ boundary) and above 700°C, it decreases the stability field of the γ phase by decreasing the solubility of nickel(@#@ γ/α + γ boundary). However below 700°C, phosphorus reverses its role in γ and acts as a γ stabilizer, increasing the nickel solubility range. The addition of phosphorus to Fe-Ni caused significant changes in the nucleation and growth processes. Phosphorus contents of 0.1 wt pct or more allow the direct precipitation ofa from the parent γ phase by the reaction γ ⇌ α + γ. The growth rate of the α phase is substantially higher than that predicted from the binary diffusion coefficients. Formerly at Planetology Branch, Goddard Space Flight Center     

The Cr−Re phase diagram

The phase diagram for the Cr−Re system has been derived from published data in conjunction with measurements on alloys cast and annealed at subsolidus temperatures (XRD, metallography, microprobe analysis, and measurement of the temperature for the onset of melting by the Pirani—Alterthum method). The phase equilibria at solidus temperatures have been determined from studies on alloys annealed at those temperatures. Phase homogeneity regions on the solidus have been identified: for (Cr) up to 43 at.% Re, for the σ phase −50–72 at.%Re, and for (Re) up to 17 at.%Cr; temperatures have also been determined for the invariant equilibria L+σ ⇆ (Cr) at 2150±15°C and L+(Re)⇆σ at 2335±15°C. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(406), pp. 65–71, March–April, 1999.     

The Dy−Zn phase diagram

The dysprosium-zinc phase diagram has been investigated over its entire composition range by using differential thermal analysis, (DTA) metallographic analysis, X-ray powder diffraction, and electron probe microanalysis (EPMA). Seven intermetallic phases have been found and their structures confirmed. DyZn, DyZn₂, Dy₁₃Zn₅₈, and Dy₂Zn₁₇ melt congruently at 1095 °C, 1050 °C, 930 °C, and 930 °C, respectively. DyZn₃, Dy₃Zn₁₁, and DyZn₁₂ form through peritectic reactions at 895 °C, about 900 °C and 685 °C, respectively. Four eutectic reactions occur at 850 °C and 30.0 at pct Zn (between (Dy) and DyZn), 990 °C and 60.0 at pct Zn (between DyZn and DyZn₂), 885 °C and 76.0 at pct Zn (between DyZn₃ and Dy₃Zn₁₁), and 875 °C and 85.0 at pct Zn (involving Dy₁₃Zn₅₈ and Dy₂Zn₁₇). The Dy-rich end presents a catatectic equilibrium; a degenerate invariant effect has been found in the Zn-rich region. The phase equilibria of the Dy−Zn alloys are discussed and compared with those of the other known RE-Zn systems (RE=rare earth metal) in view of the regular change in the relative stabilities of the phases across the lanthanide series     

The phase diagram of the Ni-VC-NbC system

Conclusions The Ni-VC_0.87-NbC_0.9 system has a ternary eutectic in the solidification of which the equilibrium phases are an Ni-base solid solution, (V, Nb)C carbide containing 10% NbC_0.9 and 90% VC_0.87, and (V, Nb)C carbide containing 20% VC_0.87 and 80% NbC_0.9. The point of the four-phase nonvariant equilibrium is in the region of the alloy containing 3% NbC_0.9 and 6% VC_0.87 and the temperature of the equilibrium is 1300±15°C. The diagram of the phase equilibria (Fig. 3) of this system has the same form as for the Ni-TiC-ZrC and Ni-TiC-HfC systems [9, 10].Translated from Poroshkovaya Metallurgiya, No. 8(296), pp. 67–79, August, 1987.     

The phase equilibrium diagram for the Fe-Nb-Ti System

Microstructure analysis, differential thermal analysis, x-ray diffraction, and electron probe microanalysis have been applied to the phase equilibria in the Fe-Nb-Ti ternary system over the complete composition range. The 950 °C isothermal section of the diagram has been constructed. Positions have been determined for the monovariant transformation lines in the melting diagram. No ternary intermetallides have been found.     

The titanium-rich end of the Ti-Cd phase diagram

Ti-Cd alloys containing up to 30 at. pct Cd have been prepared by diffusing cadmium from the vapor phase into pure titanium. Phase relations in these alloys have been explored by metallographic and X-ray techniques. Cadmium has quite a large solubility in theβ phase of titanium at 1000°C. Addition of cadmium decreases theα-β transformation temperature, forming a eutectoid at approximately 785°C. The solubility of cadmium inα titanium at the eutectoid temperature is approximately 6.5 at. pct, decreasing with decreasing temperature. The phase in equilibrium with saturatedα titanium is an intermetallic compound based on the composition Ti₂Cd.     

On the iron-carbon phase diagram

Experimental results that are obtained by electron microscopy, X-ray diffraction, and carbide analysis and indicate the precipitation of carbon atoms clusters in a hypereutectoid steel during its annealing above the eutectoid temperature are presented. These results are compared to the reported data in order to construct a new Fe-C phase diagram, where cementite forms below the eutectoid temperature due to the tendency of the Fe-C system toward ordering and carbon unbound to iron precipitates above this temperature in the form of clusters or graphite particles due to the tendency of this system toward phase separation.     

On the Mn-MnS phase diagram

Using a DTA technique the melting point of pure MnS has been determined to 1655 ±5°C. The monotectic temperature in the Mn-MnS system was found to be 1570 ±5°C. With these new data a thermodynamic analysis of the Mn-MnS system was carried out applying a previously developed thermodynamic model.     

The solid state portion of the Hf-Ta phase diagram

The solid state reactions in the Hf-Ta system were investigated by high-temperature X-ray diffraction, differential thermal analysis, and electron probe microanalysis. The results support a phase diagram with a monotectoid at about 40 at. pct Ta and an isotherm at 1083°C. A small miscibility gap was observed between about 40 and 80 at. pct Ta with a maximum temperature of about 1150°C.     

The solid state portion of the Hf-Ta phase diagram

The solid state reactions in the Hf-Ta system were investigated by high-temperature X-ray diffraction, differential thermal analysis, and electron probe microanalysis. The results support a phase diagram with a monotectoid at about 40 at. pct Ta and an isotherm at 1083°C. A small miscibility gap was observed between about 40 and 80 at. pct Ta with a maximum temperature of about 1150°C.     

Low-temperature extension of the lehrer diagram and the iron-nitrogen phase diagram

Iron layers are nitrided in mixtures of ammonia and hydrogen at low temperatures, using a thin nickel caplayer as a catalyst. In the coordinate field of inverse temperature vs nitriding potential, we determined the boundaries between areas in which the α, γ′, or ε phases are in thermal equilibrium. Using these data, the Fe-N phase diagram is extended from 350 °C to 240 °C and extrapolated down to 200 °C. The α, γ′, and ε phases probably coexist in a triple point in the Lehrer diagram around 214 °C.