van Ja Johan Beek

Phase equilibria in the Cu-Fe-Ti system at 1123 K

The isothermal cross-section through the ternary phase diagram Cu-Fe-Ti at 1123 K was constructed by means of a special diffusion technique developed earlier. The results have been verified on essential points by the investigation of equilibrated alloys. Five ternary intermetallic compounds designated as T~ (Ti33Cu67_xFex; 1<x<2.5), Tz (Ti40Cu~_xFex; 5<x< 17), T3 (Ti43Cus7__xFeA 21 <x < 24), ~-(Ti37Cu63_xFeA 6 <x < 7) and z~ (Ti45Cu55_xFeA 4 <x < 5) exist as equilibrium phases in this system at 1123 K. Nearly 38 at.% Cu can be dissolved in cubic TiFe. This leads to an expansion of the lattice. It was found that at 1123 K the Cu-based solid solution is in equilibrium with intermetallic compounds of the binary Ti-Fe system and with the terna=y phases T2 and T3.

The interaction between SiC and Ni, Fe, (Fe,Ni) and steel: Morphology and kinetics

Abstract The interaction between SiC and metals based on Ni or Fe has been studied from a thermodynamic and kinetic point of view. In solid-state diffusion couples the reactions have been studied in the temperature range 700 to 1035°C. In SiCNi couples the phases Ni 2 Si, Ni 5 Si 2 and Ni 3 Si are formed. The carbon is present as precipitates in regular bands in the Ni 2 Si and Ni 5 Si 2 layers. In SiCFe couples the layers consist of α-(Fe,Si) with random carbon precipitates. In SiCFe x Ni 100 − x couples at 850°C a variety of phases has been found. Dependent on the value of x , α-(Fe,Ni,Si), γ-(Fe,Ni,Si), (Fe,Ni) 5 Si 2 , (Fe,Ni) 2 Si and the ternary phase τ-(Fe 5 Ni 3 Si 2 ) are formed. Carbon is present, either as isolated particles (in Ferich layers) or in regular bands (in Ni-rich layers). The interaction between SiC and steel 316 is also investigated. The reaction zone consists of Fe silicides, Ni silicides, Cr carbides, Cr silicides, Mo silicides and Mo carbides. The kinetics of the foregoing reactions have been studied. The kinetics of the SiC(Fe,Ni) reactions are not simply intermediate between the kinetics of SiCNi and SiCFe. The reaction layer in SiC-steel couples stops growing after a short time. This is attributed to the formation of the chromium carbides.

On the layer sequence and morphology in solid-state displacement reactions

In displacement reactions of the type pA+BqX→qB+ApX, two main forms of the layer sequence have been found in the reaction layer, namely, A/ApX/B/BqX and A/B/ApX/BqX. In this paper it is argued that the thermodynamics of the system, more specifically the dependence of the activity of element X on the mole ratio between the elements A and B, determines the initial layer sequence. Various morphological variants of the two basic types may develop because of the kinetics. The prediction of the layer sequence and morphology made on the basis of this theory has been verified on a number of oxidic and sulfidic systems. It is, however, pointed out that these predictions also can be applied to purely metallic ternary systems and to other types of reactions.

Phase equilibria in the Ni-Cr-Ti system at 850°C

Abstract The isothermal cross-section through the ternary phase diagram Ni–Cr–Ti at 850°C was constructed by means of diffusion couples and equilibrated alloys. No ternary phases exist in the system at this temperature. The topology of the isotherm is largely determined by the presence of the TiCr 2 -Laves phases which are in equilibrium with the binary Ti–Ni intermetallics. About 10 at.% of Ni can be dissolved in the hexagonal β-TiCr 2 at 850°C, and the solubility of nickel in cubic α-TiCr 2 is approximately 4 at.%. A small amount of nickel or chromium increases the stability of the b.c.c. β-Ti structure. At this temperature the β-Ti(Ni)-based solid solution can dissolve up to 18 at.% of Cr.

Solid-state displacement reactions in the Fe-Ni-S and Cu-Ni-S systems between 400 and 500 degrees C

Solid-state displacement reactions of the type A+BS→B+AS have been studied in the systems Fe-Ni-S and Cu-Ni-S. In diffusion couples, mainly of the type Fe/Ni3S2 and Cu/Ni3S2, the layer sequence, morphology, and growth rate of the reaction products have been investigated. The layer sequence of the reaction products in the couples appears to be just the reverse of that found previously in displacement reactions in some couples of oxide systems like Ni/Cu2O and Co/Cu2O. We find the sequence A/B/AS/BS, whereas in the oxide systems the sequence A/AO/B/BO has been found. This means that the metal atoms exchange and sulfide ions practically stand still in the first case, whereas in the oxide system the transport of oxygen is essential. For a correct interpretation of the results it was necessary to determine the isothermal cross-section through the Fe-Ni-S system at 460 and 500°C. At 500°C the iron stabilized high-temperature modification β-Ni3S2 was found.

On the sequence of the product layers in solid-state displacement reactions

Abstract Displacement reactions of the type A + BX → AX + B have been investigated. Experiments have been carried out which affirm on the one hand the relation between the phase diagram of the system A-B-X and the layer sequence in a diffusion couple A/BX, and on the other hand permit to identify the rate-limiting step in the reaction process. To this end one of the reaction products has been applied as an initial layer on one of the couple halves before the heat treatment. In a sandwhich couple arrangement the effect of this initial layer on the morphology and thickness of the reaction zone has been directly compared with a true couple A/BX. The couples investigated up to now are Ni/Cu 2 O at 1000°C, Fe/Ni 3 S 2 at 460°C and Cu/Ni 3 S 2 at 500°C.

Phase relations in the Ag-Fe-Ti system at 1123 K

Abstract Phase equilibria in the AgFeTi system at 1123 K were determined by using polyphase diffusion couples and equilibrated alloys. The experimental observations are in agreement with a thermodynamic evaluation performed on this system. No ternary phases are present on the AgFeTi isotherm at 1123 K. The solubility of iron in the binary intermetallic compounds Ti 2 Ag and TiAg as well as the solubility of silver in Fe 2 Ti are negligible. The maximum silver content in FeTi was estimated as ≈0.5 at.%, while nearly 6 at.% of silver can be dissolved in the β-Ti(Fe) based solid solution at this temperature.

The interaction between SiC and Ni or Fe and their alloys

• A submitted manuscript is the authors version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publishers website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.