The deoxidation thermodynamics of cerium and lanthanum in liquid iron

The deoxidation thermodynamics of the Fe?Ce?O and Fe?La?O systems are estimated by combining the free energies of solution of cerium and lanthanum in iron, obtained from the respective phase diagrams, with the standard free energies of formation of cerium and lanthanum oxides given in the literature. Values for the deoxidation constants (w/o Ce)²·(w/o O)³ and (w/o La)²·(w/o O)³ of about 1×10^?20 are predicted at steelmaking temperatures. These predicted values are much lower than those obtained experimentally. It is suggested that refractory interactions, and sampling and analytical difficulties, in both laboratory and industrial determinations of these deoxidation constants, lead to erroneously high results.     

Thermochemistry of binary alloys of lanthanum with 3d-transition metals

The enthalpy of mixing for liquid binary alloys of lanthanum with 3d-transition metals (Sc, Ti, V, Cr, and Fe) is determined by a calorimetric method within the field of compositions rich in lanthanum. Data for the partial enthalpy of mixing in the La-3d-metal system with infinite dilution demonstrates a complex relationship of a change in it in the series of 3d-metals connected with gradual filling of the 3d-zone due to alloy formation with lanthanum. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 65–71, May–June, 2006.     

Deoxidation equilibria of cerium,lanthanum, and hafnium in liquid iron

Review of existing thermochemical data on the deoxidation of iron melts with rare earth metals and hafnium. Discussion of contradictory literature data on the deoxidation equilibria of cerium and lanthanum. New experimental determinations of the deoxidation equilibria of Ce, La and Hf in liquid pure iron using the solid electrolyte measuring technique and chemical analysis. Confirmation of the strong deoxidizing power of Ce, La and Hf in iron melts. Calculation of the Gibbs free energies of dissolution for cerium, lanthanum, and hafnium in liquid iron.     

Equilibria between cerium or neodymium and oxygen in molten iron

Autoradiographs show that there is an obvious reaction between Ce and Nd in liquid iron and the MgO/CaO crucible wall. For reaching the Ce-O, Nd-O equilibrium, a long melting period and the addition of rare earth elements (RE’s) in several batches were needed to ensure the full reaction between the RE’s in the melt and crucible wall. The dissolved Ce or Nd content in iron was measured by means of radioactive isotopes¹⁴¹Ce or¹⁴⁷Nd and electrolysis in the organic electrolyte. The oxygen activity was measured by solid electrolyte sensors made of ZrO₂(MgO) tube. The relationships between the equilibrium constants and the temperatures for reactions Ce₂O₃ (s) = 2[Ce] + 3[O], CeO₂ (s) = [Ce] + 2[O], and Nd₂O₃ (s) = 2[Nd] + 3[O], as well as the corresponding thermodynamic parameters, have been determined. Formerly Graduate Student at the University of Science and Technology Beijing     

The effect of zirconium,cerium, and lanthanum on the solubility of oxygen in liquid iron

The effect of zirconium, cerium, and lanthanum up to about 1 wt pet on the solubility of oxygen in liquid iron in equilibrium with an oxide phase at 1680°C was measured. All three elements are strong deoxidizers of iron, and the oxygen solubility minimums were 10 ppm or less at 0.05 to 0.1 wt pet of the alloying element. The interaction coefficients were estimated from the results giving e_o ^zr = −3, e_o ^Ce = −3, and e_o ^La = −5. When the concentration of the alloying element is expressed in wt pet, the effect of each of the three elements (Zr, Ce, and La) on the activity and solubility of oxygen in liquid iron is similar to that of aluminum.     

Effect of iron addition on the precipitation behavior of CoNiCr alloys containing Nb

The effect of iron addition on the precipitation behavior of Co-Ni-Cr-Nb alloys is discussed. Iron addition changes the main precipitate from orthorhombic β-Ni₃Nb (Ni₃Cb) to BCTγ″-phase which is disc shaped and precipitates on {100} matrix planes. The growth ofγ″-precipitate follows the Lifshitz-Wagner theory of diffusion controlled growth. An attempt has been made to analyze the structure ofγ″ using the electronic considerations of the Engel-Brewer theory. On continued aging, metastableγ″ transforms to a stable β-phase on {111} matrix planes. The orientation relationship of this phase is similar to that observed in other alloys. In addition to intragranular precipitation, β=phase also precipitates at the grain boundaries and grows into the grains. The transformation ofγ″ into β-phase does not affect the hardness to any significant extent.     

Estimation of partial excess Gibbs energy of solutes in infinitely dilute liquid iron base binary alloys

The partial excess Gibbs energy Δ?_B^Ex as well as the relationship between the partial enthalpy of mixing ΔH?_B and the partial excess entropy of solution ΔS?_B^Ex of various solute elements in liquid Fe, Al and Pb binary alloys were evaluated from a new solution model, in which ΔS?_B^Ex can be calculated from the values of ΔH?_B by Miedema's semi-empirical method and some relevant physical properties of the components in the alloys. These calculated values of Δ?_B^Ex were found to be in reasonable agreement with the selected values presented so far. The present model gives the values of Δ?_B^Ex, for which the experimental data are not yet available.     

Dendritic solidification in binary alloys

Alloys generally solidify dendritically, and associated with that is the microsegregation of impurities. Pure metals also solidify in dendritic form as “thermal” dendrites, which actually segregate the system’s enthalpy. In this investigation, small additions of solute to succinonitrile have been studied and dendritic growth observed in a supercooled melt. This free dendritic growth-mode is similar to that experienced by equiaxed dendrites found in alloy castings. Observations of these free dendrites include measurement of velocity and tip radius of the dendrites at different supercoolings and solute concentrations.     

测定钢铁及合金中酸溶铝方法的比较

对光度法,滴定法,ICP—AES,ICP—MS这几种常用测定钢铁及合金中酸溶铝方法的优缺点,方法要点和干扰情况以及消除干扰的办法进行了比较和研究。着重研究了ICP—AES法的干扰情况以及消除干扰的办法。     

Elastic constants of binary iron-base alloys

The Young’s modulus (E) and shear modulus (G) of isotropic Fe and binary Fe-C, Fe-Co, Fe-Cr, Fe-Ir, Fe-Mn, Fe-Ni, Fe-Pt, Fe-Re, Fe-Rh, and Fe-Ru alloys have been determined as functions of composition (0 to 10 at. pet) and temperature (77 to 473 K) by a pulse-echo technique (100 kHz elastic waves). Poisson’s ratio (v) and the bulk modulus (K) have been derived from the values of E and G. The rates of change of E and G with composition (ΔE/Δc and ΔG/Δc) depend on the change of lattice parameter with composition and upon the position of the solute in the periodic table. Both negative and positive values of ΔE/Δc and ΔG/Δc are observed. The values of ΔE/Δc and ΔG/Δc are generally different so that Poisson’s ratio may increase or decrease with composition. Comparable changes in the value ofK/G also occur. These changes cannot be used to predict the effects of alloying additions on the toughness of iron. The temperature dependence of E andG of the alloys is similar to that of iron, decreasing in a nonlinear manner from 77 to 473 K.     

Electrical properties of iron doped apatite-type lanthanum silicates

The effect of Fe doping on the electrical properties of lanthanum silicates was investigated. The apatite-type lanthanum silicates La10Si6-xFexO27-x/2 (x=0.2, 0.4, 0.6, 0.8, 1.0) were synthesized via sol-gel process. The unit cell volume increased with Fe doping because the ionic radius of Fe3+ ion is larger than that of Si4+ ion. The conductivities of La10Si6-xFexO27-x/2first increased and then decreased with the in-creasing of Fe content. The increase of the conductivity might be attributed to the distortion of the cell lattice, which assisted the migration of the interstitial oxygen ions. The decrease of the conductivity might be caused by the lower concentration of interstitial oxygen ions. The op-timum Fe doping content in lanthanum silicates was 0.6. La10Si5.4Fe0.6O26.7 exhibited the highest ionic conductivity of 2.712×10-2 S/cm at 800 ℃. The dependence of conductivity on oxygen partial pressure p(O2) suggested that the conductivity of La10Si6-xFexO27-x/2 was mainly con-tributed by ionic conductivity.     

Nitrogen solubility and aluminum nitride precipitation in liquid iron alloys containing nickel and aluminum

The solubility of nitrogen in liquid iron-base Fe-Ni-Al alloys has been measured up to the solubility limit for formation of aluminum nitride using the Sieverts’ method. Measurements were conducted over the temperature range from 1843 to 2023 K and aluminum concentration range from 1.5 to 3.0 wt pct Al. The effect of nickel additions was determined at 2, 5 and 10 wt pct Ni. The cross interaction parameter describing the effect of nickel and aluminum on the activity coefficient of nitrogen in iron was determined. The first and second order effects of nickel on the activity coefficient of aluminum also were determined. The solubility product of aluminum nitride increases with increasing aluminum content and increasing temperature. Addition of nickel decreases the solubility products of aluminum nitride in lower aluminum content alloys. However, the effect of the cross interaction terme _Al ^NiAl becomes significant with increasing aluminum content and compensates for the effects of the first and second order nickel-nitrogen and nickelaluminum interaction terms. Therefore the effect of nickel additions show little effect on the solubility products of aluminum nitride in higher aluminum alloys.     

Enthalpies of formation of liquid binary (copper + iron, cobalt, and nickel) alloys

The enthalpies of formation of liquid binary (Cu+Fe, Co, Ni) alloys are studied by direct reaction calorimetry in the whole range of compositions at 1873, 1823, and 1753 K, respectively. The integral molar enthalpies of mixing are found to be positive in all three systems with the maximum values approaching 10.8±0.7 kJ/mol⁻¹ at x _Fe=0.43, 7.1±0.9 kJ/mol⁻¹ at x _Co=0.55, and 3.7±0.5 kJ/mol⁻¹ at x _N1=0.53. Partial molar enthalpies at infinite dilution constitute 59.4±3.3 kJ/mol⁻¹ for iron, 44.3±4.1 kJ/mol⁻¹ for cobalt, and 14.9±2.2 kJ/mol⁻¹ for nickel in liquid copper. Similar values for copper in liquid iron, cobalt, and nickel are 36.6±3.9, 45.3±6.0, and 17.7±4.4 kJ/mol⁻¹, respectively. The results are compared with the thermodynamic data available in literature and discussed in connection to the equilibrium-phase diagrams. In particular, decreasing from Cu-Fe to Cu-Ni liquid alloys positive values of the excess thermodynamic functions of mixing are fully in accord with the growing stability of phases in these systems. The excess entropies of mixing are estimated by combining the established enthalpies with carefully selected literature data for the excess Gibbs functions. Analysis of possible contributions to the enthalpies of mixing indicates that the experimentally established regularity in ΔH values along the 3d series is likely to arise from the difference in d-band width and d-electron binding energy of the alloy constituents.