The paper deals with problems related to application of aluminum-silicon alloys for combustion engine cylinder liners

The paper presents results of a study concerning an AlSi7Mg alloy and the effect of subjecting the liquid metal to four different processes: conventional refining with hexachloroethane; the same refining followed by modification with titanium, boron, and sodium; refining by purging with argon carried out in parallel with modification with titanium and boron salts and strontium; and parallel refining with argon and modification with titanium, boron, and sodium salts. The effect of these four processes on compactness of the material, parameters of microstructure, and fatigue strength of AlSi7Mg alloy after heat treatment. It has been found that the highest compactness (the lowest porosity ratio value) and the most favorable values of the examined parameters of microstructure were demonstrated by the alloy obtained with the use of the process including parallel purging with argon and modification with salts of titanium, boron, and sodium. It has been found that in the fatigue cracking process observed in all the four variants of the liquid metal treatment, the crucial role in initiation of fatigue cracks was played by porosity. Application of the process consisting in refining by purging with argon parallel to modification with Ti, B, and Na salts allowed to refine the microstructure and reduce significantly porosity of the alloy extending thus the time of initiation and propagation of fatigue cracks. The ultimate effect consisted in a distinct increase of the fatigue limit value.

In the dissertation it has been shown, that so called “time-thermal treatment” (TTT) of the alloy in liquid state as overheating the metal

with around 250o

C above Tliq. and detailing it in temperature for 30 to 40 minutes has the influence on changing the crystallization

parameters (Tliq., TEmin.

, TEmax., TE(Me), TSol.). It was ascertained, that overheating the AlSi17Cu5Mg alloy substantially above Tliq. results

with microcrystalline structure. Evenly distributed in the eutectic warp primeval silicon crystals and supersaturated with alloying additives

of base content (Cu, Mg, Fe) of α(Al) solution, ensures not only increase durability in ambient temperature, but also at elevated

temperature (250o

C), what due to it’s use in car industry is an advantage.

Paper present a thermal analysis of laser heating and remelting of EN AC-48000 (EN AC-AlSi12CuNiMg) cast alloy used mainly for

casting pistons of internal combustion engines. Laser optics were arranged such that the impingement spot size on the material was a

circular with beam radius rb changes from 7 to 1500 m. The laser surface remelting was performed under argon flow. The resulting

temperature distribution, cooling rate distribution, temperature gradients and the depth of remelting are related to the laser power density

and scanning velocity. The formation of microstructure during solidification after laser surface remelting of tested alloy was explained.

Laser treatment of alloy tests were perform by changing the three parameters: the power of the laser beam, radius and crystallization rate.

The laser surface remelting needs the selection such selection of the parameters, which leads to a significant disintegration of the structure.

This method is able to increase surface hardness, for example in layered castings used for pistons in automotive engines.

Production of defect free castings requires good understanding of casting characteristics like mold filling ability and volume deficit characteristic. Pin test piece with cylindrical cores proposed by Engler and Ellerbrok was used to study the mold filling ability. Volume deficit characteristics experiments were conducted using the method designed by Engler. Alloy composition, Mold coat and Pouring temperature were considered as process parameters for the present study and experimental plan has been taken up through design of experiments. The alloy composition is most significant in influencing the mold filling ability, where as pouring temperature is for volume deficit. The Correlation Co-efficient value obtained is -0.98901 indicating strong a negative relation between mold filling ability and volume deficit characteristics. Negative values indicate a relationship between mold filling ability and volume deficit such that as values for mold filling ability increase, for volume deficit decrease.

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.

In the dissertation it has been shown, that so called „time-thermal treatment” (TTT) of the alloy in liquid state, as overheating the metal

with around 250o

C above the Tliq. and detaining it in this temperature for around 30 minutes, improves the mechanical properties (HB, Rm,

R0,2). It was ascertained, that overheating the AlSi17Cu5Mg alloy aids the modification, resulting with microcrystalline structure. Uniform

arrangement of the Si primeval crystals in the warp, and α(Al) solution type, supersaturated with alloying elements present in the base

content (Cu, Mg) assures not only increased durability in the ambient temperature, but also at elevated temperature (250o

C), what is an

advantage, especially due to the use in car industry.

Nowadays, the most popular production method for manufacturing high quality casts of aluminium alloys is the hot and cold chamber die casting. Die casts made of hypereutectoid silumin Silafont 36 AlSi9Mg are used for construction elements in the automotive industry. The influence of the metal input and circulating scrap proportion on porosity and mechanical properties of the cast has been examined and the results have been shown in this article. A little porosity in samples has not influenced the details strength and the addition of the circulating scrap has contributed to the growth of the maximum tensile force. Introducing 80% of the circulating scrap has caused great porosity which led to reduce the strength of the detail. The proportion of 40% of the metal input and 60% of the circulating scrap is a configuration safe for the details quality in terms of porosity and mechanical strength.

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 a study of the crystallization and microstructure of the AlSi9 alloy (EN AC-AlSi9) used for the alfin processing of iron ring supports in castings of silumin pistons. Alfin processing in brief is based on submerging an iron casting in an Al-Si bath, maintaining it there for a defined time period, placing it in a chill mould casting machine and immersing it in the alloy. This technology is used for iron ring supports in the pistons of internal combustion engines, among others. Thermal analysis shows that when the AlSi9 alloy contains a minimal content of iron, nucleation and increase in the triple (Al)+Fe+(Si) eutectic containing the -Al8Fe2Si phase takes place at the end of the crystallization of the double (Al)+(Si) eutectic. Due to the morphology of the ”Chinese script” the -Al8Fe2Si phase is beneficial and does not reduce the alloy’s brittleness. After approx. 5 hours of alfin processing, the -Al5FeSi phase crystallizes as a component of the +Al5FeSi+(Si) eutectic. Its disadvantageous morphology is ”platelike” with sharp corners, and in a microsection of the surface, ”needles” with pointed corners are visible, with increases the fragility of the AlSi9 alloys.

The paper concerns the problem of discontinuity in high pressure die castings (HPDC). The compactness of their structure is not perfect, as

it is sometimes believed. The discontinuities present in these castings are the porosity as follow: shrinkage and gas (hydrogen and gas-air

occlusions) origin. The mixed gas and shrinkage nature of porosity makes it difficult to identify and indicate the dominant source. The

selected parameters of metallurgical quality of AlSi9Cu3 alloy before and after refining and the gravity castings samples (as DI - density

index method), were tested and evaluated. This alloy was served to cast the test casting by HPDC method. The penetrating testing (PT) and

metallographic study of both kinds of castings were realized. The application of the NF&S simulation system allowed virtually to indicate

the porosity zones at risk of a particular type in gravity and high-pressure-die-castings. The comparing of these results with the experiment

allowed to conclude about NF&S models validation. The validity of hypotheses concerning the mechanisms of formation and development

of porosity in HPDC casting were also analyzed.

The impact of casting conditions on microstructure a and mechanical properties was described, especially for cast products from AlSi9Cu3 alloy. Particular attention was paid to the parameters of dendritic structure: DAS 1 and DAS 2. Selected mechanical properties (by static tension test) of test castings made using basic technologies of casting: GSC - gravity sand casting, GDC - gravity die-casting and HPDC - high-pressure die-casting, are presented for cast-on test bars and cast separately. Casts were made of the same alloy AlSi9Cu3. Fractures and the zone near the fracture (after static tension test) was subjected to VT - visual tests, PT - penetration tests and metallographic tests. The condition of porosity (fracture zone) was also assessed. The analysis of virtual results was performed using the NovaFlow & Solid system together with the database and they were compared to experimental tests. This way of validation was applied in order to assess the correlation between the local rate of cooling and the size of DAS for GSC, GDC and HPDC technologies. Finally, the correlation between the parameters of structure and mechanical properties with regard to the impact of porosity was signalized.