High‐entropy alloy AlCrFeCoNi powder with a metastable body centered cubic (bcc) structure is produced by inert gas atomization. This state is largely preserved after processing the powder by high‐velocity‐oxygen‐fuel (HVOF) thermal spraying. A heat treatment is conducted with the objective to form a duplex structure comprising a ductile face centered cubic (fcc) phase. The formation of an additional fcc phase is accompanied by a decrease in hardness and a significant improvement of wear resistance. The alternative processing route, spark plasma sintering (SPS), causes a duplex bcc and fcc structure. Detailed analyses of phase formation and wear behavior for all production routes contribute to a better understanding of microstructural effects in high‐entropy alloys.

In this study, the wear behaviour of a powder metallurgically produced AlCoCrFeNiTi0.5 high-entropy alloy (HEAs) is investigated at elevated temperatures. Spark plasma sintering (SPS) of inert gas atomised feedstock enables the production of dense bulk material. The microstructure evolution and phase formation are analysed. The high cooling rate in the atomisation process results in spherical powder with a microstructure comprising two finely distributed body-centred cubic phases. An additional phase with a complex crystal structure precipitates during SPS processing, while no coarsening of microstructural features occurs. The wear resistance under reciprocating wear conditions increases at elevated temperatures due to the formation of a protective oxide layer under atmospherical conditions. Additionally, the coefficient of friction (COF) slightly decreases with increasing temperature. SPS processing is suitable for the production of HEA bulk material. An increase in the wear resistance at elevated temperature enables high temperature applications of the HEA system AlCoCrFeNiTi0.5.

In the present study, 35vol% SiCp/AlSi7Mg0,6 composites were prepared using field assisted sintering technique in order to investigate the effect of different particle fractions and size distributions of the AlSi7Mg matrix powder on the tensile properties of the produced composite material. In most usecases the size of the reinforcement phase is given by the application and is only variable within narrow limits (< 20pm particle size in this work). On the other hand, there is potential for optimization of the matrix powder. In this investigation, fine (d50 = 25 µm), coarse (d50 = 52 µm), bimodal (50wt% of fine + 50wt% of coarse, d50 = 36 µm) and as received (d50 = 40 µm) aluminum powder was used as the matrix powder. Using fine matrix powder has improved yield strength by 5 % and ultimate tensile strength by 7 % compared to the as received condition. This is largely due to the lower porosity of the composite produced under the use of the fine matrix powder ((0.07 ± 0.04) %) in contrast to the composite using the as received aluminum powder ((0.62 ± 0.35) %). At the same time, the consumed heating energy of the composite was decreased by almost a third when using the fine matrix powder in comparison to the use of the as-received matrix powder. This paper presents results of an optimization approach for mechanical properties of aluminum matrix composites without any changes of the sintering parameters.

High-strength age-hardenable aluminium alloys are susceptible to localised corrosion. It is vital to monitor the evolution of the corrosion depth in order to prevent a critical degradation of the mechanical properties. This study presents the application of 3D optical pattern profilometry for the analysis of the pitting corrosion behaviour of the aluminium alloy EN AW-2024-T3. Therefore, measurements were conducted using a 1 M NaCl solution at different exposure times. The measurements are compared to the results of optical microscopy investigations of metallographic specimens as well as laser scanning microscopy measurements. In immersion bath tests, the 3D pattern profilometry shows a high measurement accuracy of the pitting corrosion. Regarding the pit characteristics, corroded metal sheets exhibit an increase in the pit depth, volume and area with an increasing exposure time of up to 312 h and then decrease. Moreover, a higher increase in the width in rolling direction than perpendicular to it is noticeable.

Abstract. In this study, the behaviour of the residual yield strength of aluminium alloy EN AW-2024-T3 affected by the morphology and numbers of corrosion pits (defects) is presented. Since specific defect structures are not reproducible during experimental corrosion tests, metal sheets with different numbers of pits and pit shapes are produced using laser micro structuring. The defect structures are measured using laser scanning microscopy. To compare the stress states of the micro structured and real corroded metal sheets, FE-analysis is used. Afterwards, uniaxial tensile tests are carried out and critical defect parameters in terms of yield strength reduction of the investigated aluminium alloy are detected.