Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

621.9 <063> --- 621.77 <063> --- Academic collection --- 621.77 <063> Rolling, extruding, drawing and other plastic forming except forging and sheet-metal working--Congressen --- Rolling, extruding, drawing and other plastic forming except forging and sheet-metal working--Congressen --- 621.9 <063> Working or machining with chip formation. Abrasive working. Cutting, grinding, sheet working. Thread-forming etc. Operations, tools, machines, equipment--Congressen --- Working or machining with chip formation. Abrasive working. Cutting, grinding, sheet working. Thread-forming etc. Operations, tools, machines, equipment--Congressen

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Engineering --- Congresses --- 658.567 --- 658.567 Treatment of wastes, residues, scrap. Utilization of wastes --- Treatment of wastes, residues, scrap. Utilization of wastes --- Conferences - Meetings

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Starting from existing challenges and limitations in light metal recycling (in particular aluminium and magnesium alloys), this PhD thesis aims to address these and explore new opportunities by sustainable metal management and solid-state recycling (SSR) methods. This PhD also quantifies the potential environmental benefits of the explored strategies and SSR techniques by Life Cycle Assessment (LCA). More specifically: During pyro-metallurgical recycling of aluminium alloys, the refining/melt purification options of aluminium alloys, restricted by thermodynamic barriers, are very limited compared to other base metals such as steels. As the removal from the melt of most elements is problematic, it is crucial to control their concentration in the scrap streams prior to remelting. Thus, scrap sorting is important to avoid additional (eventually impossible) refining, quality degradation (down-cycling), and dilution of the residual elements with primary aluminium addition. It is therefore described that establishing of well-optimised, harmonised recycling loops is of prime importance from an environmental perspective. Based on these arguments, Chapter 2 addresses this issue by developing a decision support model that aids in the direction of environmental conscious metal clustering. It aims: i) to express and quantify in a LCA framework, dilution and quality losses that occur during open loop recycling, and ii) to determine the optimal material input for the recycling process based on the input/output metal composition. By compositionally closing the recycling loops, it is feasible to minimise primary resource addition (primary aluminium and alloying elements) by maximising the scrap utilisation. A multi-objective optimisation approach (goal programming) is selected as the most appropriate method to prioritise the optimisation goals. After performing the environmental modelling of the secondary aluminium production as a reference route, Chapter 3 moves on to ‘meltless’ or ‘solid state recycling’ techniques for high grade aluminium production scrap. This approach is studied to achieve a significant material and energy savings by omitting/bypassing the conventional recycling step. Annually more than 40% of liquid aluminium is scrapped during the initial production-fabrication-manufacturing steps. Especially for fine form scrap from material removal processes, their very high surface-to-mass ratio results in significant unrecoverable oxidation losses during remelting. In this context, this work investigates the applicability of Spark Plasma Sintering (SPS) as an alternative SSR technique for aluminium alloy chips (Chapter 3). This allows the direct fabrication of bulk, near-net shape and semi-finished products directly from machining chips. The improved consolidation achieved via SPS is associated with the combined action of plastic deformation and the electric field during SPS processing. Microstructural investigations as well as the mechanical behaviour of the SPS blanks confirm successful solid state chips welding. Furthermore, this work also investigates applications of SPS in scrap consolidation and binding. Chapter 4 examines the use of atomised aluminium powder as a binding material/matrix for the machining chips. Chapter 5 describes the consolidation via SPS of larger scrap types (sheet metal scrap). After developing a reliable SPS route for SSR of aluminium alloy scrap, Chapter 6 analyses the environmental performance of the SPS route along with major SSR routes for aluminium alloys (recycling via hot extrusion and via screw extrusion). For this reason a LCA study was conducted where the examined SSR routes are compared with their corresponding remelting routes as reference. Mg alloys confront similar challenges in recycling as aluminium alloys. Taking also into account the wide range of magnesium applications and their higher scrap value compared to aluminium scraps; Chapter 7 focuses on broadening the material palette of SSR via SPS into Mg alloys. In this respect, this work studies the consolidation of machining chips for two Mg systems (i.e., pure Mg and AZ31 Mg alloy). This includes the microstructural evolution in different metal recycling steps (initial ingot, chips, SPSed samples) as well as the mechanical behaviour of the recycled samples versus their parent material. Finally, the conclusions, the contributions to the state of the art as well as proposed future research topics are discussed in Chapter 8.

Theses