The paper proposes a methodology useful in verification of results of dilatometric tests aimed at determination of temperatures defining

the start and the end of eutectoid transformation in the course of ductile cast iron cooling, based on quenching techniques and

metallographic examination. For an industrial melt of ductile cast iron, the effect of the rate of cooling after austenitization at temperature

900°C carried out for 30 minutes on temperatures TAr1

start and TAr1

end was determined. The heating rates applied in the study were the

same as the cooling rates and equaled 30, 60, 90, 150, and 300°C/h. It has been found that with increasing cooling rate, values of

temperatures TAr1

start and TAr1

end decrease by several dozen degrees.

This paper presents a study of the effect of the modification and cooling rate on the grain count α(Al) in the Al-5Cu alloy. Research was

performed on castings with walls thickness between 3 mm and 25 mm. Cooling curves were recorded to determine the cooling rate and the

degree of undercooling at the beginning of solidification. It has been shown that cooling rate increases exponentially as the wall thickness

of casting decreases. Moreover it has been demonstrated that the cooling rate of castings changes within a wide range (21ºC/s - 1ºC/s)

when the wall thickness changes from 3 up to 25 mm. Metallographic examinations revealed primary grains (primary α(Al) grains). The

paper show that the relationship between the grain count and the degree of undercooling (for non-modified and modified alloys) can be

represented by the equation N = Nv = np·exp(-b/ΔTα), based on the Weibull's distribution of the size of nucleation sites.

The presence of the chunky graphite is unwanted in the cast iron with the spheroidal graphite for this significantly lowers the properties of

the ductile iron. This shape of the graphite is formed as the result of the slow cooling rate of the castings with large thermal point and also

due to the presence of the elements which suppress the formation of the spheroidal graphite and support formation of the chunky graphite.

The spheroidal graphite present in the ductile iron assures the excellent mechanical properties, while the chunky graphite significantly

reduces those properties of the ductile iron. Therefore it is of importance to assume conditions under which prevented is the formation of

the chunky graphite. The casts were carried out under the conditions of the regular operation of the foundry and tested were various types

of modifiers and inoculators and also pre-inoculators containing the elements suppressing the formation of the chunky graphite (Al, Sb a

Ba). Applied were also the chromium breaker core to suppress the formation chunky graphite which was present in the structure in the

places after the feeders elimination. As whole, executed were eight casts with various types of the modifiers and inoculators.

The influence of the chill on the AlSi7Mg alloy properties after the heat treatment T6, was realised in the system of the horizontally cast plate of dimensions 160x240 mm and thickness of 10 and 15 m. The cooling course in individual casting zones was recorded, which allowed to determine the solidification rate. Castings were subjected to the heat treatment T6 process. Several properties of the alloy such as: hardness BHN, density, tensile strength UTS, elongation %E were determined. The microstructure images were presented and the structural SDAS parameter determined. The performed investigations as well as the analysis of the results allowed to determine the influence zone of the chill. The research shows that there is a certain dependence between the thickness of the casting wall and the influence zone of the chill, being not less than 2g, where g is the casting wall thickness. The next aim of successive investigations will be finding the confirmation that there is the dependence between the casting wall thickness and the influence zone of the chill for other thicknesses of walls. We would like to prove that this principle is of a universal character.

The paper deals with the effect of microstructure diversified by means of variable cooling rate on service properties of AlSi7Mg cast alloy

refined traditionally with Dursalit EG 281, grain refining with titanium-boron and modified with sodium and a variant of the same alloy

barbotage-refined with argon and simultaneously grain refining with titanium-boron and modified with strontium. For both alloy variants,

the castings were subject to T6 thermal treatment (solution heat treatment and artificial aging). It turned out that AlSi7Mg alloy after

simultaneous barbotage refining with argon and grain refining with titanium-boron and modified with strontium was characterised with

lower values of representative microstructure parameters (SDAS – secondary dendrite arm spacing, λE, lmax) and lower value of the

porosity ratio compared to the alloy refined traditionally with Dursalit EG 281 and grain refining with titanium-boron and modified with

sodium. The higher values of mechanical properties and fatigue strength parameters were obtained for the alloy simultaneously barbotagerefined

with argon and grain refining with titanium-boron and modified with strontium.

The cooling rate is one of the main tools available to the process engineer by means of which it is possible to influence the crystallisation

process. Imposing a desired microstructure on a casting as early as in the casting solidification phase widens significantly the scope of

technological options at disposal in the process of aluminium-silicon alloy parts design and application. By changing the cooling rate it is

possible to influence the course of the crystallisation process and thus also the material properties of individual microstructure

components. In the study reported in this paper it has been found that the increase of cooling rate within the range of solidification

temperatures of a complex aluminium-silicon alloy resulted in a decrease of values of the instrumented indentation hardness (HIT) and the

instrumented indentation elastic modulus (EIT) characterising the intermetallic phase occurring in the form of polygons, rich in aluminium,

iron, silicon, manganese, and chromium, containing also copper, nickel, and vanadium. Increased cooling rate resulted in supersaturation

of the matrix with alloying elements.