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.

The paper presents an analysis of the effect of shape of primary silicon crystals on the sizes of stresses and deformations in a surface layer

of A390.0 alloy by Finite Elements Method (FEM). Analysis of stereological characteristics of the studied alloy, performed based on a

quantitative metallographic analysis in combination with a statistical analysis, was used for this purpose. The presented simulation tests

showed not only the deposition depth of maximum stresses and strains, but also allowed for determining the aforementioned values

depending on the shape of the silicon crystals. The studied material is intended for pistons of internal combustion engines, therefore the

analysis of the surface layer corresponded to conditions during friction in a piston-cylinder system of an internal combustion engine having

power of up to 100 kW. The obtained results showed important differences in the values of stresses and strains up to 15% between various

shape of the silicon crystals. Crystals with sharp edges caused higher stresses and deformation locally than those with rounded shapes.

Casting porosity is the main factor influencing the fatigue properties of Al-Si alloys. Due to the increasing use of aluminum castings, porosity characterization is useful for estimating their fatigue strength. In principle, a combination of metallographic techniques and statistical pore analysis is a suitable approach for predicting the largest defect size that is critical for the casting. Here, the influence of modifiers and casting technology on the largest pore size population in AlSi7Mg alloy specimens is obtained and discussed adopting the Murakami's approach. However, porosity evaluation is a challenge in the case of microshrinkage pores, which are frequently found in industrial castings. Their complicated morphology prevents a reliable definition of an equivalent defect size based on metallographic techniques. This contribution reports the application of X-ray tomography to the 3D reconstruction of real pores in cast Al-Si alloys and provides insight into the complication of microshrinkage pore sizing by metallography.

The paper presents the results of the crystallization process of silumin by the TDA thermographic method and the results of the cast

microstructure obtained in the sampler ATD-10, that was cooling down in ambient air. The study was conducted for silumins AlSi8 and

AlSi11 unmodified. The work demonstrated that the use of thermal imaging camera allows for the measurement and recording the

solidification process of silumin. Thermal curve was registered with the infrared camera and derivative curve that was calculated on the

base of thermal curve have both a very similar shape to adequate them TDA curves obtained from measurements using a thermocouple.

Test results by TDA thermographic method enable quantitative analysis of the kinetics of the cooling and solidification process of hypoand

neareutectic silumins.

Issues connected with high quality casting alloys are important for responsible construction elements working in hard conditions.

Traditionally, the quality of aluminium casting alloy refers to such microstructure properties as the presence of inclusions and intermetallic

phases or porosity. At present, in most cases, Quality index refers to the level of mechanical properties – especially strength parameters,

e.g.: UTS, YS, HB, E (Young’s Modulus), K1c (stress intensity factor). Quality indexes are often presented as a function of density.

However, generally it is known, that operating durability of construction elements depends both on the strength and plastic of the material.

Therefore, for several years now, in specialist literature, the concept of quality index (QI) was present, combines these two important

qualities of construction material. The work presents the results of QI research for casting hypoeutectic silumin type EN AC-42100

(EN AC-AlSi7Mg0.3), depending on different variants of heat treatment, including jet cooling during solution treatment.

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.

Trace elements Co, Cr were added to investigate their influence on the microstructure and physical properties of Al-Si extruded alloy. The Co, Cr elements were randomly distributed in the matrix, forms intermetallic phase and their existence were confirmed by XRD, EDS and SEM analysis. With addition of trace elements, the microstructure was modified, Si particle size was reduced and the growth rate of β-(Al5FeSi) phase limited. Compared to parent alloy, hardness and tensile strength were enhanced while the linear coefficient of thermal expansion (CTE) was significantly reduced by 42.4% and 16.05% with Co and Cr addition respectively. It is considered that the low CTE occurs with addition of Co was due to the formation of intermetallic compound having low coefficient of thermal expansion. The results suggested that Co acts as an effective element in improving the mechanical properties of Al-Si alloy.

The present work discusses results of increased temperature on shape-dimensional changes of a 110 type hose coupling, produced from EN AC-AlSi11 alloy with the use of pressure die casting technology. The castings were soaked for 3.5 h at temperatures 460°C, 475°C and 490°C. The verification of shape-dimensional accuracy of the elements after soaking treatment, in relation to raw casting, was carried out by comparing the 3D models received from 3D scanning. Soaking temperature of about 460°C-475°C results in no significant changes in the shapes and dimensions of the castings, or surface defects in the form of blisters, which can be seen at a temperature of 490°C.

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.