This article aims to evaluate the influence of remelting on the experimental Al-Si-Cu type alloy with higher iron content on mechanical properties in relation to the resulting structure. The remelting or recycling process is one of the means of reducing the production costs of the forge plant. The experimental part deals with the analysis of the results of mechanical properties, structural analysis, and the process of crystallization of structural components and their changes due to the increased iron content caused by remelting at different states of the examined alloy. The effect of remelting and ageing on microstructure was observed using a combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM), and upon deep etching and energy dispersive X-ray analysis (EDX)). Tensile strength and elongation tests point to the negative effect of alloying, a gradual increase in wt% Fe and a change in the morphology of the iron phases, which began to manifest significantly after the fourth remelting. The process of natural ageing has been shown to be effective only on alloys with a lower number of remelting cycles, whereas the application of artificial ageing has resulted in improved mechanical properties in all the test alloys.

The hypoeutectic aluminum alloy AlSi5Cu2Mg is used for the production of high-strength cylinder head castings. The alloy is unique for its specific low permitted Ti content (0.03 wt% max), which makes it impossible to refine the grain structure of this alloy using standard Al–Ti–B grain refiners. The specific chemical composition is specified by the supplier company. The aim of this paper is to find a suitable alloying element that would improve the selected properties (e.g., mechanical, and physical properties) that are crucial for cylinder head castings. The research focuses on the investigation of the effect of different Zr addition (0.05; 0.10; 0.15 and 0.20 wt% Zr in the form of AlZr20 master alloy) on the properties of AlSi5Cu2Mg in the as-cast state and after heat treatment T7. The obtained results showed that ultimate tensile strength, yield strength, hardness, and physical properties of as-cast samples do not change significantly with increasing Zr content. The experimental alloys showed a more significant increase in ultimate tensile strength, yield strength, hardness, and thermal conductivity after heat treatment T7. Zirconium-rich intermetallic phases were observed in the shape of separate thick needles or as a cluster of two crossed thinner needles.

The aim of the paper is to describe and specify the properties and microstructure of Al-Si alloy using Zr, a combination of Zr with elements used in the grafting of Al (Ti) alloys, and modification (Sr). Al-Si alloys with a combination of Zr and Ti and Sr elements represent an opportunity for the development of new aluminum alloys with a specific use. The experiment focused on the analysis of the synergistic effects of Zr with Ti and Zr with Sr on a AlSi7Mg0.3Cu0.5 alloy. The experimental alloys contained a constant Zr content of 0.15 wt. % and were alloyed with a gradual addition of Ti and Sr in the range of 0.1 to 0.3 wt. % for Ti, and 0.1 to 0.3 wt. % for Sr. The experimental samples were cast by meltable model casting technology. In variants with a constant addition of Zr 0.15 wt. % and a gradual addition of Ti, we observed an increase in the values of mechanical characteristics, with a significant decrease in ductility. When evaluating the structure of experimental alloys, Ti affected it by increasing the number of precipitated Zr phases. Experimental alloys with Zr and Sr addition were characterized by nucleation of Zr phases in angular morphology. It can be concluded that the investigated elements are expected to have a positive (strengthening) effect even at higher operating temperatures.

Aluminum alloys currently play an important role in the production of castings in various industries, where important requirements include low component weight, reduction of the environmental impact and, above all, reduction of production costs of castings. One way to achieve these goals is to use recycled aluminum alloys. The effect of natural and artificial aging of AlSi9Cu3 alloy with different ratios of returnable material in the batch was evaluated by a combination of optical, scanning, transmission microscope and mechanical tests. An increase in the returnable material in the batch above 70% resulted in failure to achieve the minimum value required by the standard for tensile strength and ductility. The application of artificial aging had a positive effect on the microstructure and thus on the mechanical properties of experimental alloys. By analyzing the results from TEM, it can be stated that in the given cases there is a reduced efficiency of θ’-Al₂Cu precipitate formation with an increase of the returnable material in the batch and in comparison with artificial aging, which is manifested by low mechanical properties.

Nowadays, high-pressure die-casting technology is an integral part of industrial production. High productivity, reduced machining requirements together with the low weight and advantageous properties of aluminium alloys form an ideal combination for the production of numerous components for various industries. The experimental part of the presented article focuses on the analysis of the change in the ratio of returnable material and commercial-purity alloy in a batch depending on the internal homogeneity of castings (microstructure, porosity and microhardness) from AlSi9Cu3(Fe) alloy. The use of returnable material in the batch is a key factor in achieving the maximum use of aluminium melt, which increases the economic efficiency of production and, last but not least, has a more favorable impact on the environment. Structural analysis showed that the increase in returnable material in the batch was visibly manifested in a change in the morphology of the eutectic Si. A negative change in the morphology of the eutectic Si particles was observed after increasing the returnable material content in the batch to 75%. The evaluation of porosity at control cuts showed the influence of the increase of returnable material in the batch, where the worst results were achieved by the alloy with 90% but also the one with 55% returnable material content in the batch.

At present, Al-Si-Cu based alloys (with a typical representative AlSi9Cu3 alloy) represent more than half of the castings used in various industries (automotive, aerospace and electrical engineering). These are most often sub-eutectic (exceptionally eutectic) alloys with a content of 6 to 13 wt. % Si and 1 to 5 wt. % Cu. The aim of the paper is to point out the importance of the evaluation of input raw materials that determines the overall properties of the casting and the costs invested in its production. A negative impact on performance can be expected when using an alloy made up of a high proportion of recycled material, despite its economic benefits. Experimental alloys were evaluated based on the results of crystallization process and a combination of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and deep etching. The effect of remelting and increasing the remelted returnable material in the batch was manifested especially in the crystallization of iron-rich phases. The negative effect of remelting on the structural components was manifested after the fourth remelting. Gradual increase of remelted returnable material in the batch causes harmful changes in the crystallization process.