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The Al–Fe–Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al–Fe–Si. A new ternary high-temperature phase τ12 (cF96, NiTi2-type) with the composition Al48Fe36Si16 was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phase τ1 with the composition Al2+xFe3Si3−x (−0.3 < x < 1.3) was studied in detail. For the binary phase FeSi2 only small solubility of Al was found in the low-temperature modification LT-FeSi2 (ζβ) but significant solubility in the high-temperature modification HT-FeSi2 (ζα) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2 is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models.

a b s t r a c tThe binary system Ni-P is one of the constituents of the ternary system Ni-P-Sn which provides the basic knowledge for understanding the interactions between Sn-based solders and common Ni(P) metallization. In this study a new version of the Ni-P phase diagram was established based on XRD, EPMA and DTA measurements. The present diagram differs in some important details from the literature version. For the phases Ni 5 P 2 high temperature (HT) and Ni 12 P 5 HT the existence of a considerable homogeneity range is proposed. In Ni 5 P 2 the transformation between HT and low temperature (LT) modification comprises a peritectic and a eutectoid reaction, whereas for the transition in Ni 12 P 5 two eutectoids are proposed. Unfortunately, the high temperature phases cannot be stabilized by quenching, so that all data have to rely on the results of thermal analyses. Furthermore, Ni 5 P 4 was found to be formed by a peritectic reaction, and a eutectic was observed between Ni 5 P 4 and NiP. The phase NiP 1.22 that had been reported in the literature could not be found at all. Although the experimental work was complicated by the high vapor pressure of phosphorus at P concentrations higher than 40 at.% (which caused the explosion of quartz tubes and prevented the preparation of equilibrium samples at higher temperatures), it could still be shown that the phase NiP 3 is probably stable down to room temperature in contrast to the literature reports.

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Being the most complex constituent of the quaternary system Ag-Cu-Ni-Sn, the ternary system Cu-Ni-Sn is the key system for the investigation of the interactions of Ag-Cu-Sn solder alloys with Ni as a contact material. Although this system has been thoroughly studied in the literature, there are still many uncertainties left. In the present work, a study of the phase equilibria in four isothermal sections at 220, 400, 500, and 700°C of the Cu-Ni-Sn system was carried out following a comprehensive literature study. The methods employed were x-ray diffraction (XRD), metallography, and scanning electron microscopy including electron probe microanalysis. The ternary solubilities of the Ni 3 Sn 2 -Cu 6 Sn 5 and Ni 3 Sn-Cu 3 Sn fields were characterized in detail. So far no continuous solubility between the respective phases has been found. At 25 at.% Sn the existence of two ternary compounds formed from the BiF 3 -type (Cu,Ni) 3 Sn phase and reported in literature could be confirmed. On the other hand, our results differ significantly from the very recent literature related to lead-free soldering.