In austenitic steels, the tetragonal Z-phase (NbCrN) has frequently been credited with beneficial strengthening effects during dislocation creep. In the modified Z-phase, niobium is partially substituted by vanadium. The basic objective of this contribution is a detailed characterization of the modified Z-phase in vanadium bearing austenitic AISI 316LN+Nb+V and HR3C steels. Experimental activities were focused on crystallography, thermodynamic and dimensional stability, kinetics of precipitation (TTP diagram) and solvus temperature of the modified Z-phase in the steels examined. Thermodynamic modelling was used for prediction of stable minor phases and solvus temperature of the modified Z-phase. Kinetics of precipitation of the (Nb,V)CrN phase in the AISI 316LN+Nb+V steel was experimentally investigated in the temperature interval of 550–1250 °C. The kinetics of precipitation of the modified Z-phase in austenitic matrix was fast. Results of diffraction studies on particles of the modified Z-phase confirmed the existence of the tetragonal unit cell already after short-term annealing. The solvus temperature of the modified Z-phase in austenitic steels was determined to be lower than that for the NbCrN phase. The decrease in the solvus temperature is dependent on the vanadium content in austenitic steels. Both thermodynamic calculations and experimental results proved that the thermodynamical stability of the modified Z-phase in austenite was high. More data are needed for evaluation of long-term dimensional stability of the (Nb,V)CrN phase in austenitic steels at temperatures for their engineering applications.

This paper focuses on the evolution of the microstructure in a grain-oriented electrical steel (GOES) thin strip after casting. After solidification, the microstructure consisted of delta-ferrite. A small fraction of austenite was formed during the cooling of the thin strip in the two-phase region (gamma+delta). Fine Cr₂CuS₄ particles precipitated in the ferrite and along the delta/gamma interfaces. Laths of primary Widmanstätten austenite (WA) nucleated directly on the high-angle delta-ferrite grain boundaries. The formation of WA laths in both adjacent ferritic grains resulted in a zig-zag shape of delta-ferrite grain boundaries due to their local rotation during austenite nucleation. Based on the EBSD results, a mechanism of the formation of the zig-zag grain boundaries has been proposed. Besides the Widmanstätten morphology, austenite also formed as films along the delta-ferrite grain boundaries. Sulfide precipitation along the delta/gamma interfaces made it possible to prove that austenite decomposition upon a drop in temperature was initiated by the formation of epitaxial ferrite. Further cooling brought the decay of austenite to either pearlite or a mixture of plate martensite and some retained austenite.

The hypoeutectic aluminum alloy AlSi5Cu2Mg is used for the production of high-strength automotive components such as cylinder head castings. AlSi5Cu2Mg alloy is characterized by a specific chemical composition (low permitted Si and Ti content) determined by the supplier. Due to the low permitted Ti content it is impossible to refine the grain structure of this aluminum alloy using standard grain refiners based on Al-Ti-B. Al-Si-Cu-Mg alloys are thermal stable up to the temperature 200°C, due to the presence of strengthening precipitates. Due to the downsizing, the operating temperature exceeds the temperature of 200°C, which leads to a decrease in the mechanical and physical properties of Al-Si-Cu-Mg alloys. The aim of this study is to analyse influence the alloying elements and heat treatment on the selected properties of AlSi5Cu2Mg alloys that are crucial for cylinder head castings. The paper focuces on the evaluation of the influence of selected alloying elements Sr, Zr and Mo on mechanical and physical properties. The present work also analysis the effect of heat treatment T6 on selected properties and structure of AlSi5Cu2Mg alloy modified by Sr, Zr or Mo. Sr, Zr and Mo were added into the AlSi5Cu2Mg alloy in the form of master alloys AlMo10, AlSr10 or AlZr20. According to the findings, the incorporation of the chosen alloying elements did not result in a substantial improvement in the mechanical and physical characteristics of AlSi5Cu2Mg alloy, which would be critical for its practical application. Physical and mechanical properties noted positive increase due to the effect of thermal processing T6.