The main aim of this paper is to present an environmentally friendly method for aluminum recycling. Development of new recycling technologies in order to increase scrap reuse potential and CO₂ emission savings are of the main importance for aluminum circular economy. In this paper, aluminum chips waste was recycled without any remelting phase in order to increase energy and material savings. The presented process is usually called solid state recycling or direct recycling. Solid state recycling process consists of chips cleaning, cold pre-compaction and hot direct extrusion followed by a combination of equal channel angular pressing (ECAP) and heat treatment. Influence of holding time during solid solution treatment and both artificial aging time and temperature on mechanical properties of the recycled EN AW 6082 aluminum chips were investigated. A comprehensive number of the experiments were performed utilizing design of experiments approach and response surface methodology. Regression models were developed for describe the influence of heat treatment parameters for presented solid state recycling process on mechanical properties of the recycled samples. Utilizing novel procedure high quality recycled samples were obtained with mechanical properties comparable with commercially produced EN AW 6082 aluminum alloy in T6 temper condition. Metallographic analysis of the recycled samples was also performed.

The utilization of aluminum-lithium-magnesium (Al-Li-Mg) alloys in the transportation industry is enabled by excellent engineering properties. The mechanical properties and corrosion resistance are influenced by the microstructure development comprehending the solidification of coherent strengthening precipitates, precipitation of course and angular equilibrium phases as well as the formation and widening of the Precipitate-free zone. The research was performed to determine the microstructure degradation of Al-2.18Mg-1.92Li alloy in a corrosive environment using electrochemical measurements. The solidification sequence of the Al-2.18Mg-1.92Li alloy, obtained using Thermo–Calc software support, indicated the transformation of the α_Al dendritic network and precipitation of AlLi (δ), Al₂LiMg (T), and Al₈Mg₅ (β) phase. All of the phases are anodic with respect to the α_Al enabling microstructure degradation. To achieve higher microstructure stability, the sample was solution hardened at 520 °C. However, the sample in as-cast condition showed a lower corrosion potential (−749.84 mV) and corrosion rate (17.01 mm/year) with respect to the solution-hardened sample (−752.52 mV, 51.24 mm/year). Higher microstructure degradation of the solution-hardened sample is a consequence of δ phase precipitation at the grain boundaries and inside the grain of α_Al, leading to intergranular corrosion and cavity formation. The δ phase precipitates from the Li and Mg enriched the α_Al solid solution at the solution-hardening temperature.

Due to the specific application of aluminum–magnesium–lithium (Al-Mg-Li) alloys in the transportation industry, it is necessary to consider the influence of microstructure development on material degradation under severe environmental conditions. This degradation was simulated according to the standard test method ASTM G34-01 (2018) on a newly designed and synthesized Al-2.1Mg-1.92Li alloy in the as-cast condition. The degradation susceptibility of the alloy was estimated by measuring the changes in the sample mass and microhardness, and the pH and chemical composition of the environment with respect to the exposure time. The influence of the microstructure constituents on the degradation of the alloy was determined using metallographic analysis of the exposed surface and cross-section of the samples after testing. During the degradation, dealloying of the α_Al matrix through Li, Mg and Al component dissolution resulted in a decrease in the mass of the samples, an increase in the pH of the environment and changes in its chemical composition. This observation was also confirmed by the results of the metallographic analysis. The degradation involved the formation of cavities around the Al₈Mg₅ (β) and Al₂LiMg (T) intermetallic phases through an anodic dissolution mechanism. The increase in microhardness values after exposure indicated an increase in the stress around the degradation front due to the wedge effect of the degradation products. The results of the investigation support the potential application of the synthesized Al-2.1Mg-1.92Li alloy under the severe environmental conditions defined by the ASTM G34-01 (2018) standard.

The corrosion behavior of the EN AW-5083 alloy was investigated due to its widespread use in marine and transportation applications. The study examined the influence of microstructure development on corrosion behavior in both as-cast and homogenized conditions. Thermodynamic calculations, differential scanning calorimetry, and metallographic characterization were used to analyze solidification and microstructure development, while electrochemical testing was applied to evaluate corrosion resistance in a solution simulating severe outdoor exposure conditions, primarily marine, industrial, and transportation environments. The results show that the as-cast microstructure contains a heterogeneous distribution of anodic and cathodic intermetallic phases, which promotes localized corrosion. Homogenization at 520 °C led to the dissolution of the Al₈Mg₅ (β) phase, resulting in reduced sensitization effects and slightly improved corrosion resistance. However, high corrosion rates were observed in both metallurgical conditions, indicating limited resistance under the applied testing conditions. The study confirms that microstructural modification through homogenization influences corrosion mechanisms in EN AW-5083.