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Recykling odlewów z kompozytów metalowych zbrojonych cząstkami i z nasycanym zbrojeniem

Nagolska D., Szweycer M.

Archiwum Technologii Maszyn i Automatyzacji

2003

Vol. 23, Nr 1

115-125

W artykule przedstawiono oryginalne zależności wyznaczające warunki przejścia cząstki stałej przez sferyczną granicę faz oraz samoczynnego wypływania ciekłej osnowy metalowej z porów zbrojenia. Zależności te mają zasadnicze znaczenie dla przebiegu recyklingu odpowiednio kompozytów zbrojonych cząstkami oraz kompozytów nasycanych. Na tej podstawie dokonano analizy stanu badań recyklingu odlewów z kompozytów zbrojonych cząstkami (recykling metodą przetopu) oraz kompozytów zbrojonych cząstkami i nasycanych (recykling metodą rozdzielenia składników). Analizę powyższą oparto na dostępnych danych literaturowych oraz badaniach autorów.

The paper presents original relationships determining transfer conditions of a solid particle through a spherical phase boundary and spontaneous flow-out of a liquid metal matrix from reinforcement pores. The relationships are of basic meaning for the course of recycling of particle reinforced and saturated composites. The above statements served as a basis for the analysis of state of the studies on recycling of the castings made of particle reinforced composites by remelt-ing and saturated by separating of the components. The above analysis was carried out on the grounds of literature sources and own studies of the authors.

Odmiany porowatości odlewów z metalowych kompozytów nasycanych

Gawdzińska K., Jackowski J., Szweycer M.

Kompozyty

2001

R. 1, nr 1

68-71

Przedstawiono krótką analizę przyczyn powstawania wad porowatości w strukturze odlewów kompozytowych uzyskiwanych przez nasycanie zbrojeń ciekłą osnową metalową. Ilustracje prezentują opisane wady, a tabela, w której zestawiono cechy charakterystyczne tych wad w połączeniu z przyczynami ich powstawania, może stanowić pomoc dla ich identyfikacji oraz opracowywania technologii nasycanych odlewów kompozytowych o najwyższej jakości.

Compactness of structure is a required feature for most of construction materials, inclusive of saturated composite castings. Structural defects of these materials frequently result from the method of their manufacture, i.e. joining two different components: a solid, usually ceramic reinforcement, and a liquid metal matrix. Analysis of porosity defects of structures of the saturated composites [1] has shown that basic reasons of their occurrence are: insufficient filling of reinforcement capillaries with liquid matrix, formation of gaseous occlusions within the composite, liberation of the gas dissolved in the matrix, and shrinkage phenomena accompanying cooling and changing the state of aggregation of the matrix. A short characteristics of the reasons mentioned above and presentation of consequences in the shape of various forms of the castings made of saturated metal composites are presented by the Authors on the ground of results of research performed by the team, composed among others of [1-4, 8], and review of literature [5, 6] related to manufacture and research of structure and properties of the castings made of saturated metal composites. The pictures in Fig. 1 show the porosity forms arising in result of insufficient filling of inter-fibre capillaries of the composite matrix, formed of thin ceramic fibres, due to too low pressure. The form of the defect shown in the picture in Fig. 2 proves that its arose due to premature solidification of saturating matrix. The pictures in Fig. 3 show the fractures of two samples of the same saturated composite, made under different pressures. They prove that too low pressure (30 MPa - Fig. 3b) does not guarantee such a structure to be free of porosity that is shown in Fig. 3a. Formation of gas occlusions in a reinforcement element under saturation is very probable. Their dimensions may be very differentiated: from macroscopic (Fig. 4) to microscopic ones (Fig. 5). However, using e.g. directional solidification of the matrix one may force their occurrence beyond the composite element (casting), as for example in a pressure head (Fig. 4). Similar procedure may be used for the most advantageous location of contraction cavities, when another ways, e.g. pressure feeding, are unfeasible. If the cooling and solidification process of the metal matrix is not accompanied by effective feeding, the shrinkage porosity of the composite casting becomes unavailable. In shrinkage pores of a composite (alumi-nosilicate reinforcement - AlSi11 alloy) crystals of solid phase from the matrix have been found, that is a proof of the presence of liquid matrix metal in the reinforcement capillaries and its withdrawal in result of the shrinkage. Specification of characteristic features of the defects of castings made of saturated metal composites is shown in Table 1 that may be helpful e.g. for developing a computer expert program related to defects of these materials.