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Interactions at the mould - modifying coating - molten nickel alloy interface

Binczyk F., Śleziona J., Gradoń P., Michalska J., Bąk S.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 3

5-10

EN

The study describes thermal-chemical interactions that take place in the molten nickel alloy-ceramic mould system, where the mould is either coated with a modifying coating ('blue' mould) or is not ('white' mould). The ceramic mould based on zirconium silicate was made by investment process at the WSK Rzeszów Foundry. The main component of the modifying coating was cobalt aluminate CoAl2O4 added in an amount of 10%. Thermodynamic calculations indicated the possibility of chemical reactions taking place between the chemically active nickel alloy constituents (Al, Ti, Hf, Ta and Nb) and the components of a ceramic mould and modifying coating. The result of such interactions is the risk of the formation of cracks on the surface of mould and molten metal penetration into these cracks, combined with the formation of casting defects, like burns-on, pitting, etc., as proved by extensive X-ray microanalysis. Changes of chemical composition in the surface layer of castings were also reported.

2

Analysis of thermal-chemical interactions at the ceramic mould – molten nickel alloy interface

Binczyk F., Śleziona J., Michalska J.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 4

5--8

EN

A model of thermal-chemical interactions at the ceramic mould – molten nickel alloy interface was described. Studies were carried out on mould coated with a layer of modifier based on zirconium silicate and cobalt aluminate. The thermodynamic calculations indicated the possibility of chemical reactions taking place between the chemically active nickel alloy constituents (Al, Ti, Hf, Ta and Nb) and components of the modifying coating. The result of such interactions is possible formation on the surface of mould and casting of "new compounds" which can be the source of casting defects, like burns-on, pitting, etc., the fact proved by extensive X-ray microanalysis. In addition, the possibility of crack formation on mould surface and of the molten metal penetration into thus formed crevices was observed.

3

Modelling of anisotropic damage by microcracks: towards a discrete approach

Bargellini R., Halm D., Dragon A.

Archives of Mechanics

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2006

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Vol. 58, nr 2

93-123

EN

Modelling of anisotropic damage by microcracks remains a pivotal topic of Damage Mechanics. Many models are built employing a single second-order tensor damage variable D and its spectral decomposition. However, some inconveniences are encountered such as non-uniqueness of the free energy or decomposition of the strain tensor. This paper first reconsiders the anisotropic damage definition; a discrete approach, which introduces nine microcrack densities associated with nine fixed directions, is presented. This definition permits to represent essential phenomena concerning quasi-brittle materials behaviour: the induced anisotropic degradation of elastic properties and the unilateral effect are notably described. In addition, the quoted inconveniences are avoided.

4

Energia zmagazynowana jako addytywny człon w wyrażeniu na potencjał termodynamiczny

Oliferuk W., Raniecki B.

Rudy i Metale Nieżelazne

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2004

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R. 49, nr 3

110-114

PL

Celem pracy jest pokazanie, na gruncie termodynamiki fenomenologicznej, roli energii zmagazynowanej w opisie termostatycznych własności materiałów. Do termodynamicznego opisu stanu próbki przyjęto zbiór następujących parametrów: YT,p identyczny {T, p alfa, H}, gdzie T - temperatura odkształconej próbki, p alfa - określone funkcje, składowych sigma ij tensora naprężenia Cauchy'ego, Hi (i=1, .... , n) jest pewną liczbą parametrów wewnętrznych, opisujących zmiany w mikrostrukturze. Bez nakładania żadnych ograniczeń na właściwości badanej próbki, wyprowadzono ogólną postać potencjału Gibbsa, ukazującą energię zmagazynowaną jako addytywny człon w wyrażeniu na ten potencjał.

EN

The aim of this paper was to demonstrate the role of stored energy in the description of thermostatic properties of materials, based on phenomenological thermodynamics. In thermodynamic description of the state of a sample, a set of the following parameters has been taken: YT,p iden {T, p alpha, H}, where T denotes temperature of a sample under deformation, p alpha are specific functions of the components sigma ij of the Cauchy stress tensor, and Hi (i=1, .... , n) represent a number of internal parameters describing microstructure changes. Without imposing any constraints on the properties of a sample examined, a general form of Gibbs potential has been derived, with stored energy represented as an additive term in the expression obtained.