Initial crystallisation or nucleation in a liquid aluminium alloy containing spinel seeds

Step-by-step in situ near-atomic-resolution observations were presented for initial crystallization or nucleation in a liquid Al-10Mg (wt%) alloy containing spinel (MgAl 2 O 4 ) seeds. Ordering of Al atoms was observed in the alloy at the interface with spinel at the superheat of 73 °C or at the melt temperature of 680 °C, where three ordered layers of Al atoms formed and disappeared alternately. When cooled to the approximate liquidus of the alloy, 607 °C, three similar but more stable ordered layers of Al atoms formed. Subsequent crystallization occurred first through the formation of partially close-packed Al atoms on the solid-like outer ordered layer of Al atoms, followed by further crystallization into more close-packed Al atoms

Characterization of Nash Equilibrium Strategy for Heptagonal Fuzzy Games

In this paper, the Nash equilibrium strategy of two-person zero-sum games with heptagonal fuzzy payoffs is considered and the existence of Nash equilibrium strategy is studied. Also, based on the fuzzy max order several models in heptagonal fuzzy environment is constructed and the existence of their equilibrium strategies is proposed. In the sequel, the existence of Pareto Nash equilibrium strategies and weak Pareto Nash equilibrium strategies is investigated for fuzzy matrix games. Finally, the relation between Pareto Nash equilibrium strategy and parametric bi-matrix games is established

Grain refinement of Al-Mg-Sc alloy by ultrasonic treatment

In foundry practice, ultrasonic treatment has been used as an efficient technique to achieve grain refinement in aluminium and magnesium alloys. This article shows the strong effect of pouring temperature and ultrasonic treatment at various temperatures on the grain refinement of Al-1 wt% Mg-0.3 wt% Sc alloy. Without ultrasonic treatment, a fine grain structure was obtained at the pouring temperature of 700 °C. The average grain size sharply decreases from 487 ± 20 to 103 ± 2 μm when the pouring temperature decreases from 800 to 700 °C. Ultrasonic vibration proved to be a potential grain refinement technique with a wide range of pouring tem- perature. A microstructure with very fine and homogeneous grains was obtained by applying ultrasonic treatment to the melt at the temperature range between 700 and 740 °C, before pouring. Cavitation-enhanced hetero- geneous nucleation is the mechanism proposed to explain grain refinement by ultrasound in this alloy. Moreover, ultrasonic treatment of the melt was found to lead to cast samples with hardness values similar to those obtained in samples submitted to precipitation hardening, suggesting that ultrasonic treatment can avoid carrying out heat treatment of cast parts.This research was supported by The Project Bridging The Gap, funded by the Erasmus Mundus External Cooperation Window Programme. Acknowledgements also to the University of Minho, for the provision of research facilities

Characterization of Nash Equilibrium Strategy for Heptagonal Fuzzy Games

In this paper, the Nash equilibrium strategy of two-person zero-sum games with heptagonal fuzzy payoffs is considered and the existence of Nash equilibrium strategy is studied. Also, based on the fuzzy max order several models in heptagonal fuzzy environment is constructed and the existence of their equilibrium strategies is proposed. In the sequel, the existence of Pareto Nash equilibrium strategies and weak Pareto Nash equilibrium strategies is investigated for fuzzy matrix games. Finally, the relation between Pareto Nash equilibrium strategy and parametric bi-matrix games is established

An Investigation on Wear Properties of A390 Alloy by Rare Alloying Elements

Hypereutectic Al\u2013Si alloys are good candidates for many applications including automotive industry and heavy wear environments. Among them, A390 is widely used for cylinder blocks, transmission pumps, and air compressor housings. Due to high silicon content, primary and eutectic Si size and their morphologies have a significant effect on wear resistance of this alloy. In this research, the effect of Sr and Sb addition on the cast A390 alloy is examined and compared with unmodified alloy. Results suggest an enhanced wear resistance in Sb addition, whereas the Sr improved the wear resistance moderately compared with unmodified alloy. The involved mechanism (at nano and micro scales) and the microstructural evolution in each condition were analyzed and discussed