Alloy phase formation

Curiously, very little TiC was observed at any stage of the treatment it does not appear to be an intermediate to alloy phase formation. A significant amount of alloy phase appears only at 900°C and above. At 1200°C, Pt3Ti is the predominant Ti phase present. 

Gschneidner Jr., K. A. (1980) Theory of alloy phase formation, Proceedings of 108th AIME Annual Meeting, ed. Bennett, L.H. (New Orleans, LA, USA). 

K. A. Gschneider, Jr., L.S. (Larry) Darken s Contribution to the Theory of Alloy Formation and Where We Are Today , in Theory of Alloy Phase Formation, TMS-AIME, Warrendale, PA, 1979, pp. 1-39. 

Nix et al. (1987) Cu-rare earth alloys Phase formation, hydride formation + + + Methanol synthesis... 

Until recently, one might have considered this immense collection of experimental information as one of the major experimentally gathered, but theoretically unexplained, bodies of data in all of the chemical sciences. As shown above, however, in recent years major progress has been made on the theory of alloys and in estabhshing empirical or semiempirical correlations for alloy phase formation this, in turn, has benefited phase diagram prediction, which remains an important goal of computational alloy theory. Two principal approaches exist, which are presently in the process of slow convergence. 

Structure and orientation of a Me deposit on S in the initial stage of 3D Me bulk phase formation can be either independent of or influenced by the surface structure of S, which can be modified by 2D Meads overlayer formation and/or 2D Me-S surface alloy phase formation in the UPD range. Epitaxial behavior of 2D and 3D Me phases exists if some or all of their lattice parameters coincide with those of the top layer of S. The epitaxy is determined by a minimum of the Gibbs function at constant temperature and pressure. 

Electrodeposited Me alloys are of great practical importance because of their unconventional electric, magnetic, mechanical and protective properties. The problem of electroplating of alloys is related to the processes of codeposition of metals from multicomponent electrolyte systems. Thermodynamic and kinetic aspects of electrochemical codeposition of metals and the processes of alloy phase formation have been discussed in details by Brenner [6.134], Gorbunova and Polukarov [6.135] and Despic [6.136]. 

There are only two known sets of R-M systems where R is extensively soluble in M and the M solubility in R is limited, these are the R-Ag and R-Au systems. For these systems the light lanthanides are only slightly soluble in silver or gold, but the heavies exhibit extensive solubilities in these two solvents. This extensive solubility is anomalous and is not expected from the theory of alloy phase formation because of... 

Gschneidner Jr, K.A., 1980c, in Theory of Alloys Phase Formation, ed. L.H. Bennett (The Metallurgical Society, Warrendale, PA) p. 1. 

Specific Features of the Thermodynamics of Metal and Alloy Phase Formation and Degradation... 

Few requisites for imder bump metallization (UBM) since alloy phase formation does not have to be considered... 

According to earlier investigations (refs.4-5) in the case of a Pd+Cu catalyst prepared by sitajltaneous reduction, four different, Cu-containing phases may form (i) bulk Cu, (ii) adsorbed Cu, (iii) disordered alloy and (iv) ordered alloy (PdCuj) phases. In the absence of Cl"" or Pd ion, no alloy phase formation occurs during consecutive reduction (ref.6). In the latter case bulk metal and adsorbed metal formations occur simultaneously. This phenomenon was observed e.g. in the case of Cu deposition by hydrogen reduction from an aqueous solution of /Cu(NHj) /(0H)2 onto a Pd/C catalyst (Fig. 1). The doublet in the range of 0.5-0.4 V points to bulk Cu deposition on various crystal faces of Pd (ref.7), whereas the peak around 0.55 V is due to ionization of the adsorbed Cu (refs.6-7). 

For nickel, cobalt, and hon-base alloys the amount of solute, particularly tungsten or molybdenum, intentionally added for strengthening by lattice or modulus misfit is generally limited by the instability of the alloy to unwanted CJ-phase formation. However, the Group 5(VB) bcc metals rely on additions of the Group 6(VIB) metals Mo and W for sohd-solution strengthening. 

Fig. 13. Arrhenius plots of the kinetics of H atom recombination on a Ni77Cu23 alloy film catalyst. Above room temperature—active NiCu film with low activation energy. Below room temperature—film deactivated owing to a 0-hydride phase formation activation energy markedly increased. After Karpinski el al. (65).

Enthalpies of formation of solid alloy phases can be calculated from enthalpies of solution of these phases in a suitable liquid metal. The pure metals and alloys listed below, which were all originally at 31°C, have each been dropped into liquid tin at 250°C, and the heat of this process has been measured. The results, which are reprinted with permission from Ref. 23, Copyright American Chemical Society, computed for 1 mole of material are as follows ... 

At present the iron-based alloys diffusion saturation by nitrogen is widely used in industry for the increase of strength, hardness, corrosion resistance of metal production. Inexhaustible and unrealized potentialities of nitriding are opened when applying it in combination with cold working [1-3], It is connected with one of important factors, which affects diffusion processes and phase formation and determines surface layer structure, mechanical and corrosion properties, like crystal defects and stresses [4, 5], The topical question in this direction is clarification of mechanisms of interstitial atoms diffusion and phase formation in cold worked iron and iron-based alloys under nitriding. 

The preliminary plastic deformation considerably effects on the phase formation, structure, microhardness and thickness of nitrided layers in -Fe and Fe-Ni alloys. The high microhardness of the diffusion layers results from the formation of the s- and y- nitrides. Iron doping with Ni leads to changing of the s-, f-phases composition. The existence of narrow intervals of deformations of 3-8 % and 20-30 %, in which the considerable (about 2 times) rise of microhardness of surface nitrided layers due to accelerated formation of s- and f-phases, was found. 

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