Jacek Chrapoński

Quantitative metallography of two-phase titanium alloys

Abstract The paper presents the results of investigations of the two-phase Ti–6Al–2Mo–2Cr–Fe alloy microstructure by means of different methods: special techniques of light and scanning electron microscopy. It has been found that for the evaluation of the grain size and lamella colonies of the α phase, an observation in polarized light with a lambda filter gives the best results. The algorithm of the image transformations enabling detection of boundaries of the lamella colonies is presented. It employs color image separation into basic colors according to the CMYK model. Also, a fully automatic way is presented for the preparation of images obtained by means of a scanning electron microscope for quantitative analysis.

Microstructure and chemical composition of phases in Ti-48Al-2Cr-2Nb intermetallic alloy

Abstract The microstructure of the alloy and chemical composition of phases in as-cast and heat-treated conditions were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. It has been shown that at high heating and cooling rates the thickness of the α 2 and γ lamellae decreases. Also, under these conditions the surface area of the grain boundaries decreases. Higher annealing temperatures in the two-phase (γ+α) range and low cooling rates led to a lamellar microstructure. Annealing near the eutectoid temperature resulted in degeneration of the initial lamellar microstructure.

Influence of casting procedure on microstructure and properties of Mg alloy–glassy carbon particle composite

Abstract The article presents the microstructure and properties of a new cast composite material with a magnesium alloy matrix (Zn 0.7 wt.%, Zr 0.06 wt.%, Nd 0.41 wt.%, Gd 0.21 wt.% and Mn 0.03 wt.%) and glassy carbon particles (10 wt.%, granulation 70–100 μm), dedicated to a technical application under dry friction conditions, manufactured under industrial conditions from a particle–metal suspension. Microstructural examination revealed that the pressure die casting method eliminates the microvoids formed in the gravity cast process both in the matrix and at the interface and also that it decreases the effect of Zr and other phases accumulating around the particles. The applied procedure of particle extraction from the composites matrix, followed by scanning electron microscopy examination with energy dispersive spectroscopy, revealed the influence of Nd and Gd on the microstructure of the particle–matrix interface. The results of the mechanical and tribological properties tests showed that the application of pressure die casting method for the processing of Mg–GCp composite products improved those properties.

Preparation of translucent YAG:Ce ceramics by reaction sintering

The paper presents preparation of YAG precursor powders mixture with ability for the reaction sintering at lower temperature. The powder mixture was mechanochemically processed and characterized for the specific surface area and crystallinity (XRD). Sintering experiments were performed on the batched powders, mechanochemically processed powders and as-synthesised YAG powders. XRD measurements and SEM/TEM studies were applied for characterization of the phase composition and development of YAG ceramics. Transmittance of the resultant ceramics was measured. It has been shown that YAG structure formed at 200 ?C lower temperature in comparison to the reference specimen and contamination by the side phases (YAM, YAP) was limited. The best translucency was achieved for the reaction sintering of the mechanochemically processed powders.

Substructure of titanium alloys after cyclic heat treatment

Abstract The fundamental structure parameter determining the properties of titanium alloys is the grain size. The grain size can be controlled by means of the lattice strain and the internal work-hardening which accompany the phase transitions occurring during repeated heating↔cooling cycles. During cyclic heat treatments, there are conditions facilitating the cumulation of internal work-hardening. The structural research carried out has shown that in the pre-treatment cycles the structural defects refer mainly to the α phase and manifest itself by an increase in the microtwin density. Larger numbers of cycles increase the dislocation density mainly in the α phase and then in the β phase.

FGM Structure Characterization by Distance Functions and Systematic Scanning Method

The distance functions such as G(r), K(r), H(r), g(r) and systematic scanning method connected with variance analysis have been used for quantitative characterization of functionally gradient materials structures. The methods have been tested on computer generated 3D model polycrystalline structures with diverse type of gradient function. Usefulness of the presented methods for quantitative description of FGM structures has been evaluated.

Study of Interaction between Liquid Magnesium Alloy and Glassy Carbon Particles

In the presented experiments, the influence of a liquid magnesium alloy with Zr and RE reinforced on glassy carbon particles (GCp) in composites obtained by the mechanical mixing of a suspension, its pressureless solidification and by pressure die casting was examined. The microstructure of the as-received GCp and after their isolation from the composite was characterized by SEM and EDS methods. The presence of a thin oxide type layer with a high RE content was found, independent of the applied composite technology.

Application of Point Sampled Intercept Method in Quantitative Description of Anisotropic Structures

The point sampled intercept method for estimation of the volume weighted mean volume of grains has been used. The results obtained for computer generated isotropic and anisotropic (with different type and level of anisotropy) 3D polycrystalline model structures have been analysed. On the basis of this analysis methodological recommendations have been formulated.