MATERIALS ENGINEERING, Vol. 18, 2011, No. 3
published on October 2011
CONTENTS and ABSTRACTS
Schmidová, E. Hanus, P. (pp. 79-84)
EFFECT OF WELDING ON THE FRACTURE BEHAVIOUR OF THE FERRITIC CORROSION-RESISTANT STEEL Full text (PDF 2420 kB) - Available online 10 August 2011
Structural instability of the ferritic corrosion-resistant steel typically results in the carbides precipitation on the coarsened grain boundaries and in the associated intercrystalline corrosion. The examined steel revealed a tendency towards a defective fracture behaviour associated with the different carbide phase distribution. In the case of a preferential distribution within the grain interior, the relaxation processes along the welding line are limited and the transgranular cleavage fracture mechanism plays a role. Intergranular distribution of secondary phases brought tendency towards intergranular decohesion.
Dobrzański, L.A., Tański1, T., Malara, S.(pp. 85-92)
EFFECT OF THE HEAT AND SURFACE LASER TREATMENT ON THE CORROSION DEGRADATION OF THE Mg-Al ALLOYS Full text (PDF 2263 kB) - Available online 1 September 2011
In this paper there is presented the corrosion behavior of the cast magnesium alloys as cast state, after heat and laser treatment. Pitting corrosion resistance of the analyzed alloys was carried out using the potentiodynamic electrochemical method (direct current), based on a anodic polarization curve. On the basis of the achieved anodic polarization curves, using the Tefel extrapolation method near to the corrosion potential, the quantitative data were determined, which describe the electrochemical corrosion process of the investigated alloys: value of the corrosion potential Ecorr (mV), polarization resistance RP (kohm.cm2), corrosion current density icorr (10-6A/cm2), corrosion rate Vcorr (mm/year) as well the mass loss Vc (g/m2<).
Mihaliková, M., Német, M., Zubko, P., Ambriško, Ľ, Pešek, L.(pp. 93-96)
USING THE VIDEOEXTENSOMETRY AND UCI - HARDNESS FOR MONITORING OF AUTOMOTIVE STEEL SHEETS Full text (PDF 131 kB) - Available online 1 September 2011
The paper deals with examination of relation between the hardness and the size of plastic zone during the tensile loading. UCI (Ultrasonic Contact Impedance) micro-hardness method was used for hardness measurements. Deformation was evaluated by non-contact extensometry method – videoextensometry. The result present existence of the power lawl relation between hardness and plastic deformation: HV = HVp+ kEa. Hot rolled sheet and thin automotive sheet were investigated.
Greger, M., Kander, L., Snášel, V., Černý, M. (pp. 97-104)
MICROSTRUCTURE EVOLUTION OF PURE TITANIUM DURING ECAP Full text (PDF 2548 kB) - Available online 2 September 2011
The main goal of the presented paper was to describe deformation behaviour of the commercial purity titanium during the ECAP method. Attention was paid particularly on reached mechanical properties of above mentioned material. Design of experiments rested in extrusion at temperature in range from room temperature up to 280°C. The way of approach was planned in investigation of imposed strain accumulation ability. Among used methods for determination of intended aims were tensile tests, TEM, SEM. Mechanical properties were evaluated using standard tensile tests as well as small punch tests. Correlation between mechanical properties from tensile test and punch test was developed. Depending on imposed strain (e = 2 up to 8) was found that mechanical properties (namely tensile strength) have increased up to 960 MPa. Developed ECAP process enables controlling morphology of microstructural constituents and workability of titanium Grade 1.
Tischler, D., Budinská, Z., Vlčák, P., Štěpánek, I.(pp. 105-109)
NANOINDENTATION TEST FOR DLC COATING ANALYSIS Full text (PDF 293 kB) - Available online 2 September 2011
In this report the effects of the substrate on the microhardness of Diamond like carbon (DLC) thin films were investigated. The DLC coatings were deposited by Radio Frequency Plasma Actived Chemical Vapor Deposition (RF PACVD; 13,56 MHz) process on three mechanically polished substrates, which were chosen for comparison; hardened molybdenum high speed steel AISI M2, unhardened tool steel AISI L2 and titanium alloy TiAl6V4. The aim of the present investigation was to determine the influence of substrates on microhardness and other mechanical properties of DLC layer. These properties especially microhardness were studied and compared from nanoindentation load – displacement curves. Results show that the hardness of the substrate is the crucial value for the hardness of the DLC films.
Lukáč, P., Trojanová, Z. (pp. 110-114)
INFLUENCE OF GRAIN SIZE ON DUCTILITY OF MAGNESIUM ALLOYS Full text (PDF 93 kB) - Available online 2 September 2011
The paper give a brief overview on the effect of grain size on the yield strength and the elongation to fracture (ductility) of magnesium alloys. The yield stress, flow stress and fracture stress decrese with decreasing grain size. Few investigations has been devoted to studying the dependence of ductlity on the grain size. No explanation of the reported results was given in the literature. We tried to give an empirical model describing ductility of Mg alloys on grain size. It is shown that the elonation to failure increases with inverse square root of grain size. The dependence is accounted for by the activity of non-basal slip systems.
© University of Žilina, Faculty of Mechanical Engineering, ISSN 1335-0803