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Abstract: This work is devoted to the preparation of ultrafine material based on Al–Cu–Fe quasicrystalline phase by powder metallurgy using mechanical alloying and Spark Plasma Sintering. The dependence of microstructure and phase composition of powders on the conditions of mechanical alloying was described. It was found that the Al60Cu30Fe10 quasicrystalline phase forms directly already after 2 h of milling under optimized conditions. The stability of this quasicrystalline phase was studied at various temperatures of Spark Plasma Sintering compaction process. [Copyright &y& Elsevier]

This work aims to optimize the parameters of the SHS process for the preparation of NiTi shape memory alloy to obtain a high-purity, low-porosity material. For this purpose, high heating rate (over 300 °C min−1), temperature of 1100 °C and process duration of 20 min were determined as the optimal parameters. To prevent nickel depletion of the product and to minimize the porosity, the use of coarse titanium particles (200–600 μm) with fresh surface can be recommended. SHS products were composed of NiTi with the admixture of Ti2Ni phase. The formation of this phase cannot be fully avoided in SHS preparation route. [ABSTRACT FROM AUTHOR]

Abstract: This work aims to describe the effect of alloying by transition metals (Co, Cr, Cu, Fe, Ni, Mo) on the structure and properties of TiAl15Si15 alloy prepared by SHS technique. Results show that alloying elements do not form their own phases in detectable amounts, being dissolved in titanium silicide or aluminide. Co, Cu and Ni were determined mainly in aluminide, while iron was found predominantly in the silicide phase. Chromium and molybdenum dissolve in both aluminide and silicide in almost comparable amounts. All applied alloying elements increase the wear resistance and the oxidation resistance at 1000 °C, but reduce the room-temperature mechanical properties. Molybdenum-alloyed material exhibits the best oxidation resistance, followed by chromium-containing alloy. These alloys are also characterized by exceptional thermal stability. [Copyright &y& Elsevier]

Abstract: Self-propagating high-temperature synthesis (SHS) was previously proposed as alternative preparation route for Fe–Al intermetallics. However, this process was not optimized and the mechanism and kinetics of the phases'' formation was not fully clarified up to current days. In this work, in situ high energy X-ray diffraction analysis was carried out during the SHS process and the mechanism of the intermetallic'' formation in FeAl25 powder mixture was described during rapid heating and isothermal annealing at 800 °C as well as during a slower continuous heating to 900 °C. During slower heating, the formation of Fe2Al5 and FeAl2 intermetallics starts below the melting point of aluminium. When the heating rate is high, intermetallics are created after melting of aluminium. During long-term annealing, all of the phases can be transformed to FeAl phase when fine powders were applied. Detailed mechanism is proposed in this paper and kinetics of the intermetallics'' formation is described. [Copyright &y& Elsevier]

Abstract: Alloys formed by Fe–Al intermediary phases have lower density than common metallic high-temperature alloys and good high-temperature oxidation resistance. Previously it was proved that silicon additions to these alloys enable to produce them efficiently by reactive sintering and improves the wear resistance. In this work, the oxidation resistance of the novel Fe–Al–Si alloys containing 10–30 wt. % of aluminium and 5–30 wt. % of silicon produced by the reactive sintering technology was tested. Cyclic and isothermal oxidation tests were carried out at 800 °C in air. Tested alloys exhibit excellent oxidation resistance, which increases with silicon content up to 20 wt. %. The reasons are discussed in terms of the phase composition of the oxide layer and the changes in chemical composition under the oxide layer during oxidation. [Copyright &y& Elsevier]

The structure of Ni 8 Ti 5 was solved and refined from precession electron diffraction tomography data using dynamical refinement approach. It has trigonal symmetry R -3 m ( a = 12.24(5) Å, c = 15.33(5) Å) with a structure related to the structure of Ni 4 Ti 3 . The greatest challenge of the structure determination was the assignment of atomic types due to the proximity of scattering powers of Ti and Ni. Several approaches to determination of atom type distribution over atomic positions were used; (1) analysis of the Wyckoff position multiplicities, (2) refinement of displacement parameters, and (3) geometrical analysis of the structure and comparison with known structures. These approaches consistently pointed to one distribution, which was confirmed by a significant improvement of the refinement figures of merit. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and crystallization behavior of a conventionally cast Fe-38 at.% Al-1 at.% C alloy and a set of crystals obtained from this alloy by the Bridgman and the floating-zone methods were investigated. A significant redistribution of elements during crystallization was observed. A two-phase microstructure of the κ-phase in the B2 matrix was found in regions with composition below 37 at.% Al and 0.5 at.% C. A microstructure consisting of the κ-phase and B2 matrix with a limited amount of graphite globules was obtained in the fast-solidified Bridgman sample. An enhanced growth of graphite lathes in the Bridgman crystal was observed at a growth rate of 28 mm h−1. These graphite lathes were oriented parallel to the {100} and {110} planes. The κ-phase precipitates have no orientation relationship with the matrix. [Copyright &y& Elsevier]