Stainless steels are used widely in many industries. A duplex microstructure offers a combination of advantages, including resistance to crevice and stress corrosion, reduced susceptibility to hot cracking in comparison with fully austenitic structures and excellent tensile strength. The paper discusses the effect of aging on the microstructure and corrosion resistance of X2CrNiMoN25-7-4 super duplex stainless steel. Low and predictable corrosion rate is an important parameter for steels operating in aggressive environments. Resistance to intergranular corrosion expressed by corrosion rate (mm/year) was determined in accordance with standard PN-EN ISO 3651-1. Metallographic studies were carried out to evaluate surface degradation and intergranular corrosion. The results support an evaluation of the impact that phase fraction changes caused by aging have on resistance to intergranular corrosion. The results of the corrosion analysis were used to develop mathematical models describing changes in corrosion rate over time for different phase fractions.

Results of studies on the modification of AlSi7Mg alloy with an exotherimc modifier are presented in the paper. MgO, Cr 2 O 3 , Na 2 O 2 , NaNO 3 , Na 2 MoO 4 were used as modifiers in the amount of 0.05, 0.10, 0.15, 0.20 and 0.25%, and Cr 2 O 3 +Al, NaNO 3 +Al, Na 2 MoO 4 +Al were applied as exothermic modifiers with Al as the reducing agent in the amount of 0.04-0.3%. The analyzed modifiers were incorporated in line with factorial design 2 3 . The Inmold modification method was applied. The microstructure of selected modified alloys was presented, and their tensile strength, percentage elongation and Brinell hardness number were given in graphic form. The results of the study indicate that the use of modifiers delivering an exothermic effect influences the effectiveness of silumin modification.Keywords: Al alloys, modification, silumin, exothermic modifier W pracy przedstawiono wyniki badań nad modyfikacją stopu AlSi7Mg modyfikatorem egzotermicznym. Do badań użyto, jako modyfikatorów związków MgO, Cr 2 O 3 , Na 2 O 2 , NaNO 3 , Na 2 MoO 4 wprowadzanych w ilości 0.05, 0.10, 0.15, 0.20 and 0.25% oraz w postaci modyfikatora egzotermicznego z Al jako reduktorem Cr 2 O 3 +Al, NaNO 3 +Al i Na 2 MoO 4 +Al w ilości 0.04-0.3% wprowadzanych zgodnie z planem czynnikowym 2 3 . Modyfikację prowadzono metodą Inmold. Przedstawiono wybrane mikrostruktury stopu po modyfikacji oraz w postaci graficznej wytrzymałość na rozciąganie, wydłużenie procentowe i twardość Brinella. Wykazano, że zastosowanie modyfikatora w postaci mieszanki dającej efekt egzotermiczny wpływa na efektywność modyfikacji siluminu.

This study discusses changes in the value of fractal parameters determined based on functions of structure S(t), generated in different directions of anisotropy of the examined surfaces. The analyzed material consisted of AFM calibration standards TGT1, PG and TGZ1 which were used as models of strongly isotropic and anisotropic surfaces. The topography of the examined surfaces was imaged by atomic force microscopy. The obtained results indicate that all surfaces can be described mathematically to identify fractal parameters in any anisotropic direction.

Al–Si alloys are among the most popular casting metals. Two-component aluminium alloys with silicon are not suitable for direct use after melting. Subject to their silicon content, Al Si alloys have a coarse-grained eutectic phase, and alloys with more than 13% Si content also feature large crystallites or β-phase needles. The β-phase is hard, but also fragile. Large crystallites are good planes of division, and they reduce the mechanical properties of alloys.In this study, the Al-9% Si alloy was refined with a sodium modifier. The modifier was added to the mould by the in-mould method. The modifier's influence on the microstructure and mechanical properties of the alloy was presented graphically. The results of the analysis indicate that the compound modifier influenced the evaluated properties of the Al-9%Si hypoeutectic alloy.

Results of studies on the modification of Al-7%SiMg alloy with an exothermic modifier on base Na2B4O7 are presented in the paper. The alloy was modified in a casting mold. Its structure, tensile strength and percentage elongation were determined. The results of the study indicate that in addition to modifier quantity and the type of reducing agent applied to produce an exothermic reaction, the reaction's thermal effect influences the quality of the modification process, leading to changes in the microstructure and mechanical properties of the alloy.