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 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.

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.