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Effect of Titanium and Boron on the Stability of Grain Refinement of Al-Cu Alloy

Górny M., Sikora G., Kawalec M.

Archives of Foundry Engineering

2016

Vol. 16, iss. 3

35--38

The present research was conducted on thin-walled castings with 5 mm wall thicknesses. This study addresses the effect of the influence of different master alloys, namely: (1) Al-5%Ti-1%B, (2) Al-5%Ti and (3) Al-3%B, respectively on the structure and the degree of undercooling (ΔTα = Tα-Tmin, where Tα - the equilibrium solidification temperature, Tmin - the minimum temperature at the beginning of α(Al) solidification) of an Al-Cu alloy. The process of fading has been investigated at different times spent on the refinement treatment ie. from 3, 20, 45 and 90 minutes respectively, from the dissolution of master alloys. A thermal analysis was performed (using a type-S thermocouple) to determine cooling curves. The degree of undercooling and recalescence were determined from cooling and solidification curves, whereas macrostructure characteristics were conducted based on a metallographic examination. The fading effect of the refinement of the primary structure is accompanied by a significant change in the number (dimension) of primary grains, which is strongly correlated to solidification parameters, determined by thermal analysis. In addition to that, the analysis of grain refinement stability has been shown with relation to different grain refinements and initial titanium concentration in Al-Cu base alloy. Finally, it has been shown that the refinement process of the primary structure is unstable and requires strict metallurgical control.

Outage probability analysis of system with dual selection combining over correlated Weibull fading channel in the presence of α-μ co-channel interference

Petković M., Stefanović M., Cvetković A., Krstić D., Mitić I., Stefanović Č.

Przegląd Elektrotechniczny

2013

R. 89, nr 8

126--129

In this paper, the performance of the system with dual selection combining over correlated Weibull fading channel in the presence of α-μ distributed co-channel interference is studied. The closed-form expressions for probability density function and cumulative distribution function of the signal-to-interference ratio at the output of the selection combining receiver are presented. The effect of correlation on the system performances is investigated and numerical results are shown.

Analizowano właściwości system transmisji z podwójna selekcją składającego się ze skorelowanego kanału Weibulla w obecności interferencji typu α-μ. Przedstawiono krzywe gęstości prawdopodobieństwa i skumulowana dystrybuantę stosunku sygnału do interferencji.