MATERIALS ENGINEERING, Vol. 16, 2009, No. 2
published on June 2009

CONTENTS and ABSTRACTS

Varchola, M., Besterci, M., Sülleiová, K. (pp. 1-4)
MECHANICAL ALLOYING Al-C SYSTEM AND ITS STABILITY Full text (PDF 241 kB)
The main factors of mechanical alloying Al-C system and its structural and physical metallurgical regularities are presented in this work. In the present article dependences of hardness on structural changes of Al-C system annealed at the different times and temperatures are described.

Hrnčiar, V., Lapin, J., Demian, S., Švec, P. (pp. 5-10)
ON DEVELOPMENT OF OPTIMAL METALLURGICAL PROCESS FOR PREPARATION OF A NEW GENERATION OF INTERMETALLIC ALLOYS Full text (PDF 1937 kB)
Intermetallic TiAl based alloys are used in extreme conditions, e.g. high temperature, aggressive atmosphere and combined high temperature mechanical loading. The contribution deals with development and optimization of plasma melting metallurgical process in new developed crystallizer with rotational and axial movement of melt, for preparation of new intermetallic alloys based on Ti-(45-48)Al-(1-10)Ta (at.%). The melting process parameters and their influence to final microstructure and properties of alloys are discussed. The aim of this work is to produce alloys with lower number of technological steps necessary to achieve chemical composition, homogeneity and purity as well.

Kalincova, D. (pp. 11-14)
AN INFLUENCE OF THE SURFACE ROLLING ON MECHANICAL PROPERTIES OF THE BAND SAW BLADES Full text (PDF 2759 kB)
The article present the experiment focused on the band saw blade surface mechanical properties analysis after plastic deformation process. The deformation of the band saw blade is caused by rootling in order to increase operating reliability. Mechanical properties were evaluated by hardness measurement and by microstructure analysis.

Man, O., Pantělejev, L., Pešina, Z. (pp. 15-21)
EBSD ANALYSIS OF PHASE COMPOSITIONS OF TRIP STEEL ON VARIOUS STRAIN LEVELS Full text (PDF 742 kB)
Flat test bar made of TRIP steel was sequentially strained in tension. Eeach deformation step was made on a predefined strain level in which the phase composition was measured using EBSD; the analyses were made ex-situ exactly in the same area of 30x30µm. Retained austenite (RA) was present in the form of elongated grains (plates) and roughly equiaxial ones. The RA content was initially 14.5% and decreased with imposed strain down to approximately 5% in selected strain range from 0% to 10%. This is in agreement to some extent with outcomes of both in-situ and ex-situ experiments presented by other authors, the difference beeing supposed either in data clean up or in variation in micriostruct ure of particular steel. Kernel average misorientation method was confirmed as useful tool to discern bainite and grainy ferrite in lightly deformed specimen. Problem arose in distinguishing between martensite and deformed ferrite at higher deformation levels because of high dislocation density and/or lattice distortion in both components. The ferrite and retained austenite fraction were analysed with sufficient accuracy; martensite fraction was established with high degree of uncertainty.

Šebo, P., Švec, P., Janičkovič, D., Štefánik, P. (pp. 22-25)
WETTING OF COPPER BY LEAD-FREE Sn-Cu SOLDERS AND SHEAR STRENGTH OF Cu – Cu JOINTS Full text (PDF 373 kB)
Developing and microstructure of lead-free Sn-Cu solders containing 3, 5 and 10 wt. % of copper in bulk as well as in ribbon form is presented. Wetting of copper substrate by these solders at the temperatures 300, 350 and 400°C in air (partially in N2+10H2) during 1800 s was studied by sessile drop method. Joints Cu – solder – Cu were prepared at 300°C and 1800 s in air as well as in gas mix and their shear strength was measured. The microstructure was studied by light and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analyzer and standard X-ray diffraction machine. Wetting angle decreases with increasing wetting temperature. Wetting angle increased for higher (10 wt. %) amount of copper in solder. Shear strength of the joints decreases with increasing the copper concentration in solder.

Mazancová, E., Mazanec, K. (pp. 26-31)
STACKING FAULT ENERGY IN HIGH MANGANESE ALLOYS Full text (PDF 102 kB)
Stacking fault energy of high manganese alloys (marked as TWIP and TRIPLEX) is an important parameter determining deformation mechanism type realized in above mentioned alloys. Stacking fault energy level can be asserted with a) gliding of partial and/or full dislocations, b) gliding mechanism and twinning deformation process in connection with increasing of fracture deformation level (deformation elongation) and with increasing of simultaneously realized work hardening proces., c) gliding mechanism and deformation induced e-martensite formation. In contribution calculated stacking fault energies are presented for various chemical compositions of high manganese alloys. Stacking fault energy dependences on manganese, carbon, iron and alluminium contents are presented. Results are confronted with some accessible papers.The aim of work is to deepen knowledge of presented data. The TWIP and TRIPLEX alloys can be held for promissing new automotive materials.

Martinkovič, M. (pp. 32-35)
QUANTITATIVE ANALYSIS OF DRAWING TUBES MICROSTRUCTURE Full text (PDF 584 kB)
Final properties of forming pieces are affected by production, at first conditions of mechanical working. Application of stereology methods to statistic reconstruction of three-dimensional plastic deformed material structure by bulk forming led to detail analysis of material structure changes. The microstructure of cold drawing tubes from STN 411353 steel was analyzed. Grain boundaries orientation was measured on perpendicular and parallel section of tubes with different degree of deformation. Macroscopic deformation leads to grain boundaries deformation and these ones were compared.


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