**4. The influence of exogenous inoculation on the result of endogenous inoculation in pure aluminum**

In the practice of casting is also a problem of connection of endogenous inoculation i.e. realized by use of additives, for example Ti and B with exogenous inoculation i.e. realized by use of electromagnetic field. However as presented in papers (Szajnar & Wróbel, 2008a, 2008b, Wróbel, 2010) occurs that the phenomenon of convection transport (rejection) of impurities for example Cu and inoculants for example Ti from crystallization front into metal bath volume in result of intensive, forced by electromagnetic field the movement of liquid metal. This leads to an increase in density of bases to heterogeneous nucleation of aluminum and in consequence to increase in density of grains in the central area of ingot. Results of determination of Cu and Ti concentration in near-surface and central areas of investigated ingots with use of emission optical spectrometry is a proof of such reasoning. On their basis was affirmed, that in ingot of Al with a purity of 99,5% which was cast under the influence of electromagnetic field and with (Ti + B) inoculation, the Cu and Ti concentration in central area increase was observed (Fig.22a). Whereas in Al, which was cast only with (Ti + B) inoculation, the Cu and Ti concentrations in the near-surface and central areas of ingot are similar (Fig.22b).

The second proof of convection transport (rejection) of Cu and Ti from crystallization front into liquid metal volume is the analysis of macrostructure of investigated ingots and counting of all macro-grains in equiaxed crystals zone. Macrostructure of ingot of Al with a purity of 99,5%, which was cast with the combined effect of the electromagnetic field and with (Ti+B) inoculation has smaller equiaxed crystals zone than the ingot which was cast only with the influence of endogenous inoculation, but the first ingot has a smaller size of macro-grain in its equiaxed crystals zone than the ingot which was cast only with (Ti+B) inoculation (Fig.23).

Fig. 22. Concentration of Cu and Ti in near-surface and central areas of Al with a purity of 99,5%ingots: a – after common exogenous (electromagnetic field) and endogenous (Ti + B) inoculation, b – only after endogenous (Ti + B) inoculation

Fig. 23. Macrostructure of ingot of Al with a purity of 99,5%: a – after common exogenous (electromagnetic field) and endogenous (Ti + B) inoculation, b – only after endogenous (Ti + B) inoculation

Based on conducted calculations of number of macro-grains in equiaxed crystals zone following formula was formulated:

$$n\_{e\chi+e\upsilon} > n\_{e\chi} + n\_{e\upsilon} \tag{9}$$

where:

560 Advances in Crystallization Processes

In the practice of casting is also a problem of connection of endogenous inoculation i.e. realized by use of additives, for example Ti and B with exogenous inoculation i.e. realized by use of electromagnetic field. However as presented in papers (Szajnar & Wróbel, 2008a, 2008b, Wróbel, 2010) occurs that the phenomenon of convection transport (rejection) of impurities for example Cu and inoculants for example Ti from crystallization front into metal bath volume in result of intensive, forced by electromagnetic field the movement of liquid metal. This leads to an increase in density of bases to heterogeneous nucleation of aluminum and in consequence to increase in density of grains in the central area of ingot. Results of determination of Cu and Ti concentration in near-surface and central areas of investigated ingots with use of emission optical spectrometry is a proof of such reasoning. On their basis was affirmed, that in ingot of Al with a purity of 99,5% which was cast under the influence of electromagnetic field and with (Ti + B) inoculation, the Cu and Ti concentration in central area increase was observed (Fig.22a). Whereas in Al, which was cast only with (Ti + B) inoculation, the Cu and Ti concentrations in the near-surface and central

The second proof of convection transport (rejection) of Cu and Ti from crystallization front into liquid metal volume is the analysis of macrostructure of investigated ingots and counting of all macro-grains in equiaxed crystals zone. Macrostructure of ingot of Al with a purity of 99,5%, which was cast with the combined effect of the electromagnetic field and with (Ti+B) inoculation has smaller equiaxed crystals zone than the ingot which was cast only with the influence of endogenous inoculation, but the first ingot has a smaller size of macro-grain in its equiaxed crystals zone than the ingot which was cast only with (Ti+B)

a) b) Fig. 22. Concentration of Cu and Ti in near-surface and central areas of Al with a purity of 99,5%ingots: a – after common exogenous (electromagnetic field) and endogenous (Ti + B)

inoculation, b – only after endogenous (Ti + B) inoculation

**4. The influence of exogenous inoculation on the result of endogenous** 

**inoculation in pure aluminum** 

areas of ingot are similar (Fig.22b).

inoculation (Fig.23).

nex+en – number of macro-grains in equiaxed crystals zone of ingot which was cast with common influence of exogenous (electromagnetic field) and endogenous (Ti + B) inoculation,

nex – number of macro-grains in equiaxed crystals zone of ingot which was cast only with influence of exogenous (electromagnetic field) inoculation,

nen – number of macro-grains in equiaxed crystals zone of ingot which was cast only with influence of endogenous (Ti + B) inoculation.

Summarize, was affirmed that application of common exogenous (electromagnetic field) and endogenous (Ti + B) inoculation strengthens effect of structure refinement in comparison with application of one type of inoculation, only if is used skinning of ingot surface i.e. machining in aim of columnar crystals zone elimination.
