The work presents the research results of the silumin coat structure applied on the carbidic alloy ductile iron with the metal matrix: pearlitic, bainitic and martensitic. The coats were made in the AlSi5 silumin bath at the temperature tk = 750±5°C. The holding time of cast iron element in the bath was τ = 180s. Irrespective of the kind of tested ductile iron the obtained coat consisted of three layers with a different phase composition. The first layer from the cast iron ground “g1`” is built from Fe4CSi carbide which contains selected alloy additives of the cast iron. On it the second layer “g1``” crystallizes. It consists of the AlFeSi inter-metallic phase which can appear in its pure form or contain a small quantity of the alloy additives of the cast iron. The last external part of the layer “g2” mainly consists of the hypo-eutectic phases of silumin. The AlFeSi inter-metallic phases in the form of free precipitations with a lamellar or faceted morphology can also appear there. These phases also can contain a small quantity of the alloy additives of the cast iron. More than that, in all the layers of the coat there are graphite precipitations. The phenomenon of graphite movement to the coat is caused by intensive dissolving of the cast iron element surface by the aluminum of the silumin bath.
The work presents the analysis results of the structure of the coat obtained by dipping in silumin AlSi5 of two grades of alloy cast steel: GX6CrNiTi18-10 (LH18N9T) and GX39Cr13 (LH14). The temperature of the silumin bath was 750±5°C, and the hold-up time of the cast steel element τ = 180 s. The absolute thickness of the coat obtained in the given conditions was g = 104 μm on cast steel GX6CrNiTi18-10 and g = 132 μm on GX39Cr13. The obtained coat consisted of three layers of different phase structure. The first layer from the base “g1`” was constructed of the phase AlFe including Si and alloy additives of the tested cast steel grades: Cr and Ni (GX6CrNiTi18-10) and Cr (GX39Cr13). The second layer “g1``” of intermetallic phases AlFe which also contains Si and Cr crystallizes on it. The last, external layer “g2” of the coat consists of the silumin containing the intermetallic phases AlFeSi which additionally can contain alloy additives of the cast steel. It was shown that there were no carbides on the coat of the tested cast steels which are the component of their microstructure, as it took place in the case of the coat on the high speed steels.
This paper presents the results of hypoeutectic 226 grade alloy as well as prepared on its basis Al-Si alloy containing Cr, V and Mo. The
additives tested were added as AlCr15, AlV10 and AlMo8 master alloys. Alloys tested were poured into DTA sampler as well as using
pressure die casting. An amount of Cr, V and Mo additives in alloy poured into DTA sampler comprised within the range approximately
0.05-0.35%. Alloys to pressure die casting contained 0.05-0.20% Cr, V and Mo. The crystallization process was examined using the derivative
thermal analysis (DTA). The microstructure of castings made in the DTA sampler as well as castings made with use of pressure die
casting were examined. The basic mechanical properties of castings made using pressure die casting were defined too. It has been shown
in the DTA curves of Al-Si alloy containing approximately 0.30 and 0.35% Cr, Mo, and V there is an additional thermal effect probably
caused by a peritectic crystallization of intermetallic phases containing the aforementioned additives. These phases have a morphology
similar to the walled and a relatively large size. The analogous phases also occur in pressure die casting alloys containing 0.10% or more
additions of Cr, V and Mo. The appearance of these phases in pressure die casting Al-Si alloys coincides with a decrease in the value of
the tensile strength Rm and the elongation A. It has been shown die castings made of Al-Si alloys containing the aforementioned additives
have a higher Rm and A than 226 alloy.
The work presents the results of the investigations of the effect of the nitrogen (N2) refining time „τraf” and the gas output on the course of
the crystallization process, the microstructure and the gassing degree of silumin 226 used for pressure casting. The refinement of the
examined silumin was performed with the use of a device with a rotating head. The crystallization process was examined by way of
thermal analysis and derivative analysis TDA. The performed examinations showed that the prolongation of the N2 refining time causes
a significant rise of the temperature of the crystallization end of the silumin, „tL”, as well as a decrease of its gassing degree, „Z”. An
increase of the nitrogen output initially causes an increase of the temperature „tL” and a drop of the gassing degree „Z”, which reach their
maximal values with the output of 20 dm3
/min. Further increase of the output causes a decrease of the value „tL” and an increase of „Z”.
The examined technological factors of the refining process did not cause any significant changes in the microstructure of silumin 226.
This paper presents the effect of the temperature and hold time in the holding furnace of 226 silumin on the characteristic quantities of
TDA curves. The temperature of phase transformations and the cooling rate were tested.It has been shown that increasing both the hold
time and the temperature in the holdingfurnace cause the decreasethe end ofα+Al9Fe3Si2+β and α+Al2Cu+βternary eutectics
crystallizationtemperature in the tested silumin. This is due to the fact an increase in amounts of impurities as a result of reacting theliquid
alloy with the gases contained in the air.It has been shown, however, that examined technological factors ofthe metal preparation do not
cause systematic changes in the cooling rate.
The results of statistical analysis applied in order to evaluate the effect of the high melting point elements to pressure die cast silumin on its tensile strength Rm, unit elongation A and HB were discussed. The base alloy was silumin with the chemical composition similar to ENAC 46000. To this silumin, high melting point elements such as Cr, Mo, V and W were added. All possible combinations of the additives were used. The content of individual high melting point additives ranged from 0.05 to 0.50%. The tests were carried out on silumin with and without above mentioned elements. The values of Rm, A and HB were determined for all the examined chemical compositions of the silumin. The conducted statistical analysis showed that each of the examined high melting point additives added to the silumin in an appropriate amount could raise the values of Rm, A and HB. To obtain the high tensile strength of Rm = 291 MPa in the tested silumin, the best content of each of the additives should be in the range of 0.05-0.10%. To obtain the highest possible elongation A of about 6.0%, the best content of the additives should be as follows: chromium in the range of 0.05-0.15%, molybdenum 0.05% or 0.15%, vanadium 0.05% and tungsten 0.15%. To obtain the silumin with hardness of 117 HB, chromium, molybdenum and vanadium content should be equal to about 0.05%, and tungsten to about 0.5%.
The work presents the effect of strontium and antimony modification on the microstructure and mechanical properties of 226 silumin casts.
The performed research demonstrated that strontium causes high refinement of silicon precipitations in the eutectic present in the microstructure
of the examined silumin and it significantly affects the morphology of eutectic silicon from the lamellar to the fibrous one. Sr
modification also causes an increase of: the tensile strength „Rm” by 12%; the proof stress „Rp0,2” by 5%; the unit elongation „A” by 36%
and the hardness HB by 13%. Antimony did not cause a change in the microstructure of the silumin, yet it caused an increase in Rm and
HB by 5%, in Rp0,2 by 7% and in A by 4%.
The paper presents the results of hypoeutectic silumin 226 grade and silumin produced on its basis through the addition of V and Mo.
Vanadium and molybdenum were added as the preliminary alloy AlV10 and AlMo8 in an amount providing the concentration of 0.1; 0.2;
0.3 and 0.4% V and Mo. TDA curves of tested silumins were presented; regardless of the chemical composition there were similar thermal
effects. Pressure castings microstructure research revealed the presence in silumins with the addition of V and Mo phases do not occur in
silumin without these additives. These phases have a morphology similar to the walled, and their size increases with increasing
concentration of V and Mo. The size of the precipitates of these phases silumin containing 0.1% V and Mo does not exceed 10 microns,
while 0.4% of the content of these elements increases to about 80 microns. Tests of basic mechanical properties of silumins were carried
out. It has been shown that the highest values of tensile strength Rm = 295 MPa and elongation A = 4.2% have silumin containing
approximately 0.1% V and Mo. Increasing concentrations of these elements causes a gradual lowering of the Rm and A values.
The paper presents the results of the application of a statistical analysis to evaluate the effect of the chemical composition of the die casting Al-Si alloys on its basic mechanical properties. The examinations were performed on the hypoeutectic Al-Si alloy type EN AC-46000 and, created on its basis, a multi-component Al-Si alloy containing high-melting additions Cr, Mo, W and V. The additions were introduced into the base Al-Si alloy in different combinations and amounts (from 0,05% to 0,50%). The tensile strength Rm; the proof stress Rp0,2; the unit elongation A and the hardness HB of the examined Al-Si alloys were determined. The data analysis and the selection of Al-Si alloy samples without the Cr, Mo, W and V additions were presented; a database containing the independent variables (Al-Si alloy's chemical composition) and dependent variables (Rm; Rp0,2; A and HB) for all the considered variants of Al-Si alloy composition was constructed. Additionally, an analysis was made of the effect of the Al-Si alloy's component elements on the obtained mechanical properties, with a special consideration of the high-melting additions Cr, Mo, V and W. For the optimization of the content of these additions in the Al-Si alloy, the dependent variables were standardized and treated jointly. The statistical tools were mainly the multivariate backward stepwise regression and linear correlation analysis and the analysis of variance ANOVA. The statistical analysis showed that the most advantageous effect on the jointly treated mechanical properties is obtained with the amount of the Cr, Mo, V and W additions of 0,05 to 0,10%.
This article presents the results of studies in the hypoeutectic silumin destined for pressure die casting with the simultaneous addition of
chromium and tungsten. The study involved the derivative and thermal analysis of the crystallization process, metallographic analysis and
mechanical properties testing. Silumin 226 grade was destined for studies. It is a typical silumin to pressure die casting. AlCr15 and AlW8
preliminary alloys were added to silumin. Its quantity allowed to obtain 0.1, 0.2, 0.3 and 0.4% of Cr and W in the tested alloy. Studies of
the crystallization process as well as the microstructure of the silumin poured into DTA sampler allowed to state the presence of additional
phase containing 0.2% or more Cr and W. It has not occurred in silumin without the addition of above mentioned elements. It is probably
the intermetallic phase containing Cr and W. DTA studies have shown this phase crystallizes at a higher temperature range than α (Al)
solid solution. In the microstructure of each pressure die casting containing Cr and W the new phases formed. Mechanical properties tests
have shown Cr and W additives in silumin in an appropriate amount may increase its tensile strength Rm (about 11%), the yield strength
Rp0.2 (about 21%) and to a small extent elongation A.
The study presents the results of the investigations of the effect of Cu, Ni, Cr, V, Mo and W alloy additions on the microstructure and
mechanical properties of the AlSi7Mg0.3 alloy. The examinations were performed within a project the aim of which is to elaborate an
experimental and industrial technology of producing elements of machines and devices complex in their construction, made of aluminium
alloys by the method of precision investment casting. It was demonstrated that a proper combination of alloy additions causes the
crystallization of complex intermetallic phases in the silumin, shortens the SDAS and improves the strength properties: Rm, Rp0.2,HB
hardness. Elevating these properties reduces At, which, in consequence, lowers the quality index Q of the alloy of the obtained casts.
Experimental casts were made in ceramic moulds preliminarily heated to 160 °C, into which the AlSi7Mg0.3 alloy with the additions was
cast, followed by its cooling at ambient temperature. With the purpose of increasing the value of the quality index Q, it is recommended
that the process of alloy cooling in the ceramic mould be intensified and/or a thermal treatment of the casts be performed (ageing)(T6).
The work presents the results of the examinations of silumin 226 as well as a silumin produced on its basis containing a W and Mo addition
introduced in the amount of 0.1; 0.2; 0.3 and 0.4% of both elements simultaneously. Investigations of the crystallization process of the
silumins by the TDA method were conducted. Also, a microscopic analysis of their microstructure was performed and their basic mechanical
properties were determined. Microstructure tests were made on casts produced in an TDA sampler as well as by the pressure method.
The investigations exhibited a change in the course of crystallization of the silumin containing 0.3 and 0.4% W and Mo with respect to
silumin 226 and the silumin with the addition of 0.1 and 0.2%. The presence of additional phases which did not occur in the case of lower
addition contents was established in the silumin containing 0.3-0.4% W and Mo, regardless of the applied casting technology. The tests
showed the possibility of increasing the tensile strength Rm, the proof stress Rp0,2 and the unit elongation A of the silumin as a result of a
simultaneous introduction of the W and Mo addition. The highest values of Rm, Rp0,2 and A were obtained in the silumins with the additions
of these elements within the range of 0.1-0.2% each.