Solid State Phenomena Vols. 203-204

Abstract: In this paper results of tests concerning the WC/Co fine-crystalline composite powders type 88/12 and 83/17 provided for thermal spraying of layers resistant to abrasion are presented. Tests which characterize basic technological properties were performed since these properties are essential from thermal spraying point of view. Microstructural properties are essential as well because they allow evaluation of morphology of powders by SEM method with an analysis of chemical composition in micro-areas. Moreover, the phase composition was characterized by XRD in macro scale and by EBSD in microareas including distribution maps of individual phase components in all particles of the powders.

Abstract: The present work concerns the precipitation process of the sigma phase in the ferritic-austenitic stainless steel of duplex type SAF 2205. After the preliminary thermo-mechanical treatment, the steel was subjected to cold rolling up to 85% of reduction and subsequent annealing in the temperature range 650÷950°C for various times. Significant structural changes were observed in the course of annealing treatment affecting the formation of the ferrite and austenite texture. The development of annealing textures resulted from recovery and recrystallization processes in both component phases and the precipitation of the sigma phase. X-ray investigations included the phase analysis, measurements of pole figures for case of each phase, austenite and ferrite. Microstructure of analysis was conducted by means of optical microscopy. The microstructure and texture of duplex type steel after annealing result from the precipitation process of sigma phase, depend on the temperatures and time of annealing.

Abstract: The aim of the work was to investigate the influence of the processing on the final microstructure of the melt-spun Ni-Fe-P ribbons. The melt-spinning was carried out in two ways. For the first one the alloy was molten in a simple single-chamber crucible and for the second one double-chamber crucible was used. The chemical composition of the alloy molten in the single chamber was Ni40Fe40P20. The two component melt-spinning was made starting from the Ni80P20 and Fe80P20 alloys. All of the three alloys were molten in titanium gettered argon atmosphere starting from 99.95 wt % Ni, 99.95 wt % Fe, Ni-P and Fe-P master alloys in the arc melting furnace. The alloys were melt-spun in helium. The phase composition and the microstructure of the melt-spun ribbons were investigated by X-ray diffraction (XRD), a transmission electron microscope (TEM), respectively. The fracture of the specimens were observed with use of scanning electron microscope (SEM). SEM observations of the fracture surfaces show different character of the fractured samples.

Abstract: The microstructure of 9% Cr cast steel for advanced power plants, serviced at around 580 − 600°C, after ageing has been characterized. The investigated cast steel was subject to ageing at the temperature of 600°C for 6000 and 8000 hrs. Quantitative TEM analysis of the cast steel microstructure was performed to describe the dislocation density within subgrains, the width of martensite subgrains and the M_23C6 carbides parameters (shape and mean diameter). Moreover, the phase identification was carried out using electron diffraction. The results have shown that an increase in ageing time at 600°C temperature is the reason for slight increase in the subgrain size, the size of M₂₃C₆ carbides and a decrease in dislocation density within subgrains. The MX particle size was not changed. The Laves phase was identified in the cast steel microstructure after 6000 hrs of ageing.

Abstract: The microstructure of Al₆₅Cu₂₀Fe₁₄ (numbers indicate at.%) alloy doped with 1 at.% of W was studied. The selected alloy composition should allow to obtain the quasicrystalline icosahedral phase after solidification process. The bulk samples were obtained in two stages. At first, the synthesis of alloy through premelting of component elements in induction furnace and then, the directional solidification by the Bridgman method were performed. The morphology of selected areas of the samples were studied using Scanning Electron Microscope equipped with energy dispersive X-ray spectroscope, which was used to examine chemical compositions of each analysed areas. Additionally the X-ray powder diffraction was used to identify the phases present in the alloys. It was stated that the filaments of tungsten were present in the alloys. The filaments have thickness ranged from 0.01 to 2.5 μm. As a result of investigation, the arrangement of filaments in the material was determined.

Abstract: The composites of Al-Cu-Fe alloys with fibrous reinforcement, containing quasicrystals, e.i. crystal-quasicrystal composites (CQ composites) were studied. The composites were obtained in situ by the Bridgman method. The plate-like samples were studied by tensile test performed up to rupture. Tensile fracture surface of composite and reinforcement fibers were investigated. The role of voids on the fracture morphology and the reason of its formation were discussed.

Abstract: Amorphous alloys based on iron, obtained by melt spinning technique, are modern and very promising soft magnetic materials. The thermal annealing at temperatures closed to the crystallization temperature can cause an increase of magnetic permeability more than 10 times i.e. the so called enhancement of soft magnetic properties effect (ESMP). It is usually explained by formation of iron nanocrystallites in amorphous surroundings or by formation of the relaxed amorphous phase. Such a microstructure leads to averaging out of magnetic anisotropy and cause the ESMP.

Abstract: The materials from Fe-Co-B-Si-Nb system have several interesting and useful properties such as high mechanical strength, abrasive and corrosion resistance and good electrical properties useful in many applications, for example: materials for sensors and precise current transformers. The aim of the presented work was to obtain Fe-based alloy in an amorphous state and examination atoms arrangement in its structure which has an influence on material properties. Multicomponent alloy with nominal composition of Fe37.44Co34.56B19.2Si4.8Nb4 was obtained by pressure die casting method in form of plate with thickness of d=1mm. The structure of rapidly solidified plate was examined by X-ray diffraction. This investigation revealed that the studied sample was amorphous. Based on experimental X-ray data the pair distribution function was calculated and discussion on possible atoms arrangement was carried out.

Abstract: The investigations of the microstructure changes of Ni₇₅Ti₂₅ powder prepared by mechanical alloying in as-milled state and after annealing treatment were performed. The X-ray diffraction (XRD) method was used to investigate a mechanically induced solid state reaction between nickel and titanium powders. The crystallite sizes and lattice strains were analyzed by using Williamson-Hall method. The compacted powder morphology was analyzed by SEM method. The Ni(Ti) solid solution was formed as a result of the milling process. The crystallite sizes of all alloys are below 100 nm. The annealing treatment, in the temperature range of 773 K to 1173 K leads to reduction of the breadth of Ni(Ti) diffraction lines, which indicates at the increase in size of crystallites. However, the phase composition of annealed Ti₇₅Ni₂₅ powder does not change, so the presence of any Ni-Ti intermetallic phases is not stated.

Abstract: The process of Ni₇₅Mo₂₅ powder synthesis via mechanical alloying (MA) was studied. Process was carried out from pure elements: Ni and Mo with a particle size under 150 μm. A ball-to-powder weight ratio and the rotational speed were 5:1 and 500 rpm, respectively. Oxidation was reduced by milling under an argon atmosphere. The milling process was performed during up to 60 hours. X-ray diffraction (XRD) and scanning electron microscopy techniques have been used to investigate resulting products. It was found that the particle sizes decrease with the increase in milling time. The resulting powder consists of metastable Ni(Mo) and Mo(Ni) solid solutions. Milled Ni75Mo25 powder was subjected to heat treatment at temperature of 773K, 973K and 1173K. As a result of annealing the formation of Ni₄Mo and NiMo intermetallic phases was observed.