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This article deals with powder metallurgical production and modification of properties of a composite material based on an age‐hardenable Al–Cu alloy. The main objective is to improve the mechanical properties by particle reinforcement and equal‐channel angular pressing (ECAP). Our approach makes use of four hardening mechanisms: precipitation hardening, particle reinforcement, strain‐hardening, and grain boundary hardening associated with an ultrafine‐grained microstructure produced by ECAP. The main processing steps are high‐energy ball milling, hot‐isostatic pressing, extrusion, heat treatment, and a single ECAP pass. Microstructures are analyzed by optical microscopy, scanning electron microscopy, and scanning transmission electron microscopy. The mechanical properties are characterized by hardness measurements and quasi‐static tensile testing. Our experimental results show that the proposed processing route results in a nearly homogeneous distribution of SiC particles in the matrix. The combination of particle reinforcement and ECAP leads to an improvement of ultimate tensile strength by almost 300 MPa compared to the unreinforced alloy. A subsequent heat treatment leads to a further increase in hardness and strength that can be related to changes in the defect structure. Our study provides detailed information on how processing steps, microstructures, and mechanical behavior are interrelated in this technologically relevant class of materials.

This paper describes a study for waste of electrical and electronic equipment (WEEE) to characterise the plastic composition of different mixed plastic fractions. Most of the samples studied are currently excluded from material recycling and arise as side streams in state-of-the-art plastics recycling plants. These samples contain brominated flame retardants (BFR) or other substances of concern listed as persistent organic pollutants or in the RoHS directive. Seventeen samples, including cathode ray tube (CRT) monitors, CRT televisions, flat screens such as liquid crystal displays, small domestic appliances, and information and communication technology, were investigated using density- and dissolution-based separation processes. The total bromine and chlorine contents of the samples were determined by X-ray fluorescence spectroscopy, indicating a substantial concentration of both elements in density fractions above 1.1 g/cm3, most significantly in specific solubility classes referring to ABS and PS. This was further supported by specific flame retardant analysis. It was shown that BFR levels of both polymers can be reduced to levels below 1000 ppm by dissolution and precipitation processes enabling material recycling in compliance with current legislation. As additional target polymers PC and PC-ABS were also recycled by dissolution but did not require an elimination of BFR. Finally, physicochemical investigations of recycled materials as gel permeation chromatography, melt flow rate, and differential scanning calorimetry suggest a high purity and indicate no degradation of the technical properties of the recycled polymers.

The study deals with the optimisation of medium-to highstrength aluminium wrought alloys. The goal is to define processing routes in order to improve the mechanical properties if compared to their commercial counterparts. It is shown for the Al-Mg-Si and the Al-Cu-Mg-Si system that the application of ECAP enables a significant increase in strength. The strengthening as well as the grain size reduction respectively, benefit from increasing alloying as well as from the degree of aging. It is also shown that the presence of a considerably fine particulate reinforcement hardens the material tremendously during ECAP. The combination of a pre-or post-ECAP heat treatment enables the improvement of the workability on the one hand, reducing the loads on the die, and also gives a better ductility on the other hand. This positive effect is particularly pronounced for low alloying contents and high aging temperatures and can be attributed to the interaction of deformation induced defects and the precipitation activity. The combination of an appropriate set of ECAP parameters (heat treatment condition, ECAPstrain, -temperature, -backpressure) enables the efficient production of outstanding properties. Due to the low workability of AA7075 (Al-Zn-Mg-Cu system) no significant improvement in properties was achieved.

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