R. Lück

Phase diagram of the Al-Cu-Fe quasicrystal-forming alloy system. I. Liquidus surface and phase equilibria with liquid

Abstract The microstructures of as-cast and slowly solidified Al–Cu–Fe ternary alloys in the vicinity of the icosahedral phase region have been investigated using light microscopy and scanning electron microscopy. The chemical composition of the different phases present has been determined by energy-dispersive X-ray spectroscopy with a correction of electron probe microscopy analysis. The solidification process was studied by means of the differential thermal analysis and magnetothermal analysis measurements. In contrast to the equilibrium phase diagram, fast cooling leads to the formation of a metastable β′ phase (an ordered cubic structure) rather than to the formation of the φ phase. The nucleation of ω phase is very sluggish during the solidification. The results are presented as solidification paths, superimposed onto the liquidus surface projection to demonstrate the solidification sequences.

CALORIMETRIC DETERMINATION OF THE ENTHALPIES OF FORMATION OF LIQUID NI-ZR ALLOYS

The enthalpies of formation of liquid Ni-Zr alloys have been measured through the composition range 0 < Xzr < 0.4, where Xzr is the mole fraction of Zr. Four independent runs were made at temperatures ranging from 1740 to 1743 K and one at 1838 K. The compositional dependence of the enthalpies of formation could be fitted quite well with polynomial representations according to the subregular as well as to the sub-subregular solution approximations. The influence of chemical short-range order was found to differ from the earlier Ni-Ti results.

Pure component A + classically ideal solution (B + C +⋯)= ?

A recently developed partial ideal solution model has resulted in: a pure component A + a classically ideal solution (B + C +⋯)= a partial ideal solution (A + B + C +⋯).In this paper, some new formulae are deduced and a much more quantitative verification is made using literature data. The theoretical results are in excellent agreement with room-temperature experiments for organic mixtures, organic–inorganic mixtures and aqueous solutions and in good agreement with high-temperature experimental data for alloys, molten salt mixtures and molten slags. A reasonable prediction is also made for a mixed U + Pu oxide fast-reactor fuel.

Chemical short range order in liquid Sb-Sn alloys proved with the aid of the dependence of the mixing enthalpies on temperature

Abstract The mixing enthalpies of liquid Sb-Sn alloys were measured as a function of the concentration and of the temperature by means of a high-temperature calorimeter. The deviations found from the behaviour of a regular solution and the small dependences on temperature can be interpreted assuming the existence of associates, having the compositions SbSn and SbSn 2 . The results are reproduced quantitatively by an association model.

Phase diagram of the Al-Cu-Fe quasicrystal-forming alloy system. III. Isothermal sections

The phase equilibria of the ternary Al-Cu-Fe system are demonstrated as isothermal sections at 800, 700, 645, 620, 617, 600, 592, and 560 °C. These data are based on metallographic investigation, microscopy with polarized light, and on structure analysis using X-ray diffraction, as well as on isopleths, which were constructed using thermal analyses. A Scheil reaction scheme can be used for the explanation of some novel phase transformations in the solid state.

The temperature VS time transformation (T-T-T) diagram for a transition from the amorphous to the nanocrystalline state

Nanocrystalline (NC) phases can be formed during a crystallization of amorphous alloys annealed isothermally below the usual crystallization temperature. In this work, the transformation kinetics from the amorphous state to the NC phases in a Ni-P alloy was investigated by means of a differential scanning calorimeter (DSC) and a magnetothermal analysis (MTA) method. The temperature vs time transformation (T-T-T) diagrams for the amorphous-to-NC process determined by using the two experimental methods are comparatively analyzed. In the MTA measurements, the transformation was found to start much earlier than that in the DSC measurement, and the difference in the measured starting times for the transformation from the two measurements becomes larger for low temperatures where the average grain size in the NC sample is reduced. The transformation kinetics were analyzed by means of the Avrami exponent (based on the Johnson-Mehl-Avrami equation) and the activation energy (from the Arrhenius relation). It was found that the transformation process measured in the DSC experiments is only a bulk crystallization occurring in the amorphous samples, and the early surface crystallization and a segregation process of solute P atoms fail to be detected by the DSC.

THE INTERFACIAL EXCESS ENERGY IN NANOCRYSTALLINE Ni-P MATERIALS WITH DIFFERENT GRAIN SIZES

acad sinica,rsa,natl key lab,inst met res,shenyang 110015,peoples r china.;lu, k (reprint author), max planck inst met res,inst werkstoffwissensch,seestr 92,w-7000 stuttgart 80,germany

The heat capacity of solid Ni-Ti alloys in the temperature range 120 to 800 K

Heat capacity values for solid Ni-Ti alloys are reported for the temperature range from 120 to 800 K and are based on measurements made with a Perkin-Elmer differential scanning calorimeter DSC-2 (Perkin-EImer Corp., 761-T Main Ave., Norwalk, CT). The results were extrapolated to the melting points of the three intermediate Ni-Ti phases to test for the level of compliance with an approximating procedure introduced by Kubaschewski. The heat capacity data were also used to test for compatibility among the diverse thermodynamic measurements that have been made on the Ni-Ti system.

Dürer–Kepler–Penrose, the development of pentagon tilings

Abstract As Kepler’s Aa tiling is sometimes regarded as the pentagon tiling described by Penrose, the two tilings are compared considering their acceptance domains. The acceptance domain of the Penrose tiling is a decagon, whereas the acceptance domain of Kepler’s Aa tiling looks like a 10-fold toothed wheel; it exhibits a hole in the centre and it has therefore unusual inflation properties. A related tiling proposed by Durer a century earlier than Kepler’s starts with an inflated pentagon and Durer described the possibility of glueing tiles with random distribution.

Phase diagram of the Al-Cu-Fe quasicrystal-forming alloy system. II. Isopleths

Part II deals with a set of isopleths, i. e., along the λ-i-φ tie line, ω and i tie line, i and liquid tie line, and with constant Cu content (25 at.%) and Fe (12.5, 12, 11, 10, 7.5, and 5.0 at.%) contents. These isopleths are elaborated, based on differential thermal analysis, magnetothermal analysis, optical microscopy with polarized light, and scanning electron microscopy. Isothermal sections and liquidus surface projection have been used to verify the consistency of the results.