Solid State Phenomena Vols. 203-204

Abstract: Production of primary Al- alloys belong to heavy source fouling of life environs. Care of environment in industry of aluminium connects with the decreasing consumptions resource as energy, materials, water and soil, with increase recycling and extension life of products. Recycled (secondary) aluminium alloys are made out of Al-scrap and workable Al-garbage by recycling. Applications of these alloys in recent years increase especially in automotive industry (dynamic exposed cast, engine parts, cylinder heads, pistons and so on). Controlling the microstructure of secondary aluminium cast alloy is very important, because these alloy containing more of additions elements, that forming various intermetallic phases in the structure. Improved mechanical properties of secondary alloys are strongly dependent upon the morphologies, type and distribution of the second phases, which are in turn a function of alloy composition and cooling rate. The presence of additional elements as Mg, Mn, Fe or Cu allows many complex intermetallic phases to form, which make characterization non-trivial. A combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM) upon deep etching and energy dispersive X-ray analysis (EDX)) were therefore been used for the various phases identification.

Abstract: An elemental powder mixture corresponding to the Al₃Ni₂ phase stoichiometry was subjected to mechanical alloying in a high-energy ball mill. Products of this process after various milling times were investigated by differential scanning calorimetry. The phase transformations occurring in the material throughout milling and during heating in a calorimeter were investigated by X-ray diffraction method. This study revealed that a metastable nanocrystalline NiAl intermetallic phase was formed during the mechanical alloying process. Heating of the synthesised powders in the calorimeter caused phase transformations, the product of which was an equilibrium Al₃Ni₂ intermetallic phase or a mixture of NiAl, Al₃Ni₂ and Al₃Ni intermetallic phases, depending on the milling time and the temperature up to which the material was heated.

Abstract: In the paper Gd+Ni nanoparticles were obtained using chemical reaction of Gd nanopowder in the bath based on C4H6O4Ni (pH=7) at temperature 323 K. TEM examinations show Gd+Ni nanoparticles (about 200 nm) covered by GdF3 intermediate layer and Ni-P final layer Magnetization vs. temperature (5-320 K) show the Curie point of Gd at 290 K and at low temperature a paramagnetic component related to GdF3. The obtained Gd+Ni nanopowder of 200 nm in diameter can be used in future application without fear of oxidation.

Abstract: It was shown that pulverization of the examined alloys cause a decrease of mean diameters of nanocrystallites, a change of the phase composition and affects magnetic properties. For the alloy with x=0.08 magnetization remanence at T=300 K increases about two times with remaining constant Hc while for x=0.12 Hc decreases from 1.16 t to 0.36 T. The observed effects were attributed to the phase structure changes and breaking of direct magnetic intergrain coupling

Abstract: The paper presents the results of microstructure evolution studies of hard magnetic FeCr22Co15 alloy, destructed by tension and torsion at 800 and 850°C. The temperatures and deformation rates corresponded to the condition of superplasticity of Fe-Cr-Co alloys. Observations of longitudinal section of deformed samples in scanning electron microscope showed a formation of weak gradient microstructure with highest grain refinement in the surface layer of material. Precipitation of intermetallic σ-phase was also observed, with its maximum amount in zones of the highest deformation.

Abstract: The work presents the structural, thermal and magnetic properties analysis of Fe72B20Si4Nb4 bulk metallic glasses in as-cast state and crystallization study of bulk amorphous alloy after annealing process. The studies were performed on bulk metallic glasses in of rods form with diameter of 1,5 and 2 mm. The structure analysis of the samples in as-cast state and phase analysis of studied alloy after annealing process was carried out by the X-ray diffraction (XRD) methods. Mössbauer spectroscopy (MS) was also used to investigate the local structure for studied bulk metallic glasses. Thermal properties associated with glass transition, onset and peak crystallization temperatures was examined by differential scanning calorimetry (DSC). The soft magnetic properties examination of tested material contained initial magnetic permeability and disaccommodation of magnetic permeability.

Abstract: The magnetic properties and the crystal structure of the ball-milled Tb(Ni_0.95Fe_0.05)₃ compound have been studied by using magnetization measurements and X-ray diffraction (XRD). The results were compared with those obtained for the bulk compound prepared by arc-melting technique. The investigated sample is polycrystalline and crystallizes in the rhombohedral PuNi₃ type of crystal structure (space group R-3m). With the increase of the time milling (i.e. 1 h, 24 h and 48 h) a for-mation of grains less than 1μm and a reduction of magnetocaloric effect have been observed. The analysis of XRD patterns for ball-milled powders shows that after 48h milling time there is still visible a crystalline structure.

Abstract: The aim of the paper was investigation of the effect of Cu addition on glass forming ability (GFA), thermal stability, structure and magnetic properties of Fe-Co-based bulk metallic glasses (BMGs). The raw materials used in this experiment for the production of BMGs were pure Fe, Co, Cu and industrial Fe-B, Fe-Si, Fe-Nb ferroalloy. Investigations were carried out on BMGs in rods shaped with square section with side of 1.5mm. The structure of the investigated BMGs in rod form is amorphous. The addition of small amounts of Cu is effective in changing GFA and magnetic properties. The melting temperature - Tm remained almost constant for both investigated alloy. Two alloy compositions are at or very close to the eutectics, what according to ref. [1] should guarantee the best metallic glass-forming alloys. The investigated alloys have good soft magnetic properties. The successful synthesis of the Fe36.00Co36.00B19.00Si5Nb4 and Fe35.75Co35.75B18.90Si5Nb4Cu0.6 alloys with high GFA and good soft magnetic properties by using starting industrial alloys are encouraging for the future industry applications.

Abstract: In this work we present phase structure and magnetic properties of the (Fe₈₀Nb₆B₁₄)_1-x Nd_x (x=0.08, 0.12, 0.16) bulk nanocrystalline alloys prepared by making use of mould casting technique. The applied mould allows obtaining bulk rods of 1.5 mm in diameter and about 3 cm in length. Phase structure and magnetic properties were carefully examined. It was shown that the applied preparation technique is favorable to nanocrystallization of the alloys, which was confirmed by the XRD diffraction. For all studied alloys, one can observe a formation of mainly Nd₂Fe₁₄B (hard magnetic) and Fe phases with different contributions dependently on the x parameter. It was also shown that the alloy of (Fe₈₀Nb₆B₁₄)_0.92Nd_0.08 has the best hard magnetic properties with the coercive field, magnetic saturation and maximum energy product equal to 0.2 T, 117 emu/g and 13.4 kJ/m3, respectively (at room temperature). Moreover, the coercive field and maximum energy product are gradually deteriorating with increasing of rare earth addition.

Abstract: Two Ni-based (Ni-Mn-Ga and Ni-Mn-Co-In) ferromagnetic nonstoichiometric shape memory alloys were studied in order to determine the influence of hot extrusion process on macro, microstructure and texture of the studied alloys. The microstructure of the alloys in the as cast state and after extrusion was analyzed by electron backscatter diffraction technique. Typical microstructure of the as cast alloys consisted of radially oriented columnar grains elongated perpendicularly to the casting axis. For the alloys Ni-Mn-Ga and Ni-Mn-Co-In alloys the 10M and 14M modulated martensite were observed, respectively. After extrusion Ni-Mn-Ga samples revealed high density of fibre texture parallel to the extrusion axis. In spite of applying different extrusion parameters it was not possible to avoid cracks and overcome the brittleness of the Ni-Mn-Co-In alloys.