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Open access

J. Dutkiewicz and W. Maziarz

Structure and Properties of Nano-Crystalline Ti-Base Alloys Obtained by Vacuum Hot Pressing

The cp-Ti and Ti-base alloys with additions of Ta and Nb were ball milled and consolidated using vacuum hot pressing. This novel technique allowed to obtain a high level of densification of milled powders up to about 98% and the nanometric grain size level. In the samples of vacuum hot compacted cp-Ti grain size of a single α phase was estimated at 140 nm. With the increase of content the β-stabilizing elements in alloys such as Ta and Nb, structure and a grain size has been changed. In the case of Ti-5Ta-5Nb alloy, also single α phase was observed but with grains size was much smaller, close to 85 nm. The further increasing of the content of Ta and Nb caused further refinement of grain size down to 60 nm and change of structure into two phase α+β and β in case of Ti-10Ta-10Nb and Ti-15Ta-15Nb alloys respectively. The hardness and Young Modulus were measured using the dynamic hardness tester and calculations of hardness and elastic modulus values were based on Oliver and Pharr model.

Open access

M. Bramowicz, S. Kulesza, P. Czaja and W. Maziarz

Abstract

Presented work is focused on the use of correlation methods for numerical analysis of magnetic stray field over the surface of materials. Obtained results extend our previous findings about application of the autocorrelation function and the fractal analysis for characterization of magnetic surfaces. Several domain images are recorded at various tip-sample gaps (i.e. the lift heights), and then their average widths were extrapolated down to the zero distance in order to estimate the width seen right on the surface. Apart from that, fractal parameters were derived from autocorrelation function, which turned out to be sensitive to the lift height, and might constitute universal measure (the critical lift height), above which the MFM signal became dominated by thermal noises and non-magnetic residual interactions.

Open access

T. Pisarkiewicz, T. Kenig, A. Rydosz and W. Maziarz

Solution growth of ZnO sub-micro rods enhanced by electric field

Recently the one-dimensional ZnO nanostructures have attracted much attention in gas sensor applications owing to their increased role of the surface. The authors have obtained ZnO rods of sub-micron size using the solution growth method with the growth temperature below 100°C. Investigations indicate that the rods have a well-defined hexagonal morphology and a wurtzite structure. The best uniformity and alignment of the sub-micron crystals was however obtained when electrodeposition from aqueous solution was developed. Sizes of these rods depend on the growth parameters. Moreover electrodeposition leads to a faster growth rate of ZnO sub-micron rods (2 hrs) as compared to the growth from solution (8 hrs). After electrodeposition the rods can be easily reoriented in external electric fields by using substrates with electrodes of appropriate geometry and configuration (dielectrophoretic effect). This enables the preparation of samples which can be used in gas sensor technology.

Open access

W. Maziarz, P. Czaja, T. Czeppe, A. Góral, L. Litynska-Dobrzynska, Ł. Major and J. Dutkiewicz

Alloys with constant Ni/Mn ratio equal to 1.01 of nominal compositions Ni44Mn43.5Sn12.5-xAlx (x = 0, 1, 2 and 3) were induction cast, homogenized in vacuum for 6 hours at 1000ºC, annealed for 1 h at 900 and water quenched for solution treatment (ST). Differential scanning calorimetry (DSC) studies revealed that the quenched alloys undergo martensitic transformation with martensite start temperatures (Ms) ranging from - 140 up to - 80ºC. An increase of Ms temperature with increasing of the aluminum content as well as the linear relationship between Ms and the conductive electron concentration (e/a) was observed. DSC has been used also to estimate the associated entropy change from the transformation heat Q and peak position temperature Tp; corresponding to ΔS ≈ Q/Tp. X-Ray diffraction phase analyses performed at room temperature proved that in all ST alloys the L21 Heusler structure is present. However, a different degree of order of this phase was observed, what was manifested by a decrease of intensity of the 111 superlattice reflection of the L21 structure with an increase of Al content. The ordering behavior was also proven by the transmission electron microscopy (TEM) investigations, particularly electron diffraction patterns. The evolution of microstructure after different treatments was also illustrated by light microscopy observations.

Open access

E. Olejnik, Ł. Szymański, P. Kurtyka, T. Tokarski, W. Maziarz, B. Grabowska and P. Czapla

Abstract

Refinement is one of the most energy consuming technological process, aimed at obtaining mineral raw materials of the proper grain size. Cast structural elements such as jaws or hammers in crushing machines operate under conditions of an intensive wear. The data indicate that 80 % of failures of machines and devices is caused by wearing of rubbing surfaces. This problem became the subject of several scientific and industrial investigations carried out in the whole world in order to produce materials ultra- wear resistant. Methods allowing to obtain wear resistant composite castings are discussed in the hereby paper. Within the performed research microstructures of the produced composite zones were presented and the comparative analysis with regard to mechanical and functional properties of local composite reinforcements in relation to the commercial alloys of increased wear resistance was performed. The results show almost twenty five times increase in wear resistance compared to manganese cast steel containing 18 % Mn.