Heat treatment processes, due to qualitative requirements for the cast machinery components and restrictions on energy consumption resulting on the one hand from environmental concerns, and on the other hand from a requirements coming from minimization of manufacturing costs, are resulting in searching after a technologies enabling obtainment of satisfactory results, in form of improved mechanical properties mainly, while minimizing (limiting) parameters of successive operations of the heat treatment. Heat treatment of the T6 type presented in this paper consists in operations of heating of investigated alloys to suitably selected temperature (range of this temperature was evaluated on the base of the ATD method), holding at such temperature for a short time, and next rapid cooling in water (20 oC) followed by artificial ageing, could be such technology in term s of above mentioned understanding of this issue. Performed T6 heat treatment with limited parameters of solutioning operation resulted in visible increase in tensile strength Rm of AlSi7Mg, AlSi7Cu3Mg and AlSi9Cu3(Fe) alloys.
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 paper presents research on the effects of soft annealing parameters on a change of the impact strength KC and Brinell hardness (HB)
of the EN AC-AlSi11 alloy. The research has been performed according to the trivalent testing plan for two input parameters –
temperature in the range between 280°C and 370°C and time in the range between 2 and 8 hours. The application of such heat treatment
improves the plasticity of the investigated alloy. The improvement of the impact strength KC by 71% and the decrease of the hardness HB
by 20% was achieved for the soft annealing treatment conducted at a temperature 370°C for 8 hours, compared to the alloy without the
heat treatment. A change of the form of eutectic silicon precipitations which underwent refinement, coagulation and partial rounding, had
a direct effect on the hardness HB and impact strength KC. The results obtained were used to prepare space plots enabling the temperature
and time for soft annealing treatment to be selected with reference to the obtained impact strength KC and hardness HB of the alloy with
the heat treatment.
The presented work describes the results of examination of the mechanical properties of castings made either of AlSi9Mg alloy matrix
composite reinforced with short carbon fibre or of the pure AlSi9Mg alloy. The tensile strength, the yield strength, Young’s modulus, and
the unit elongation were examined both for initial castings and for castings made of the remelted composite or AlSi9Mg alloy. After
preparing metallographic specimens, the structure of the remelted materials was assessed. A few non-metallic inclusions were observed in
the structure of the remelted composite, not occurring in the initial castings. Mechanical testing revealed that all the examined properties of
the initial composite material exceed those of the non-reinforced matrix. A decrease in mechanical properties was stated both for the metal
matrix and for the composite after the remelting process, but this decrease was so slight that it either does not preclude them from further
use or does not restrict the range of their application.
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.
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.
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