TY - BOOK

T1 - Crossover alloys

T2 - a new approach for future aluminum alloys

AU - Stemper, Lukas

N1 - embargoed until 15-03-2024

PY - 2021

Y1 - 2021

N2 - Over the last decades the accelerated development of the traffic and transportation sector has caused significant alterations in the global climate due to ever rising emissions of CO2. Even though increasing political awareness and rising economic necessity have boosted research and development in this sectors, current technologies are still not capable of fully addressing this challenge. One way to substantially improve energy savings thus reduce the level of harmful emissions are significant optimizations in vehicle design which is strongly connected to the materials used. Light weighting by deploying low-density materials such as aluminum alloys to substitute high-density steel is a well-established approach to mitigate greenhouse emissions. Unfortunately, multiple operational demands and engineering criteria, in particular those promoting strength and ductility, limit the benefits of light weighting due to the restricted property portfolio of commercial aluminum alloys and requires the unbeneficial utilization of a multi-material-mix thus limiting the recyclability at the end of a product’s lifetime. Overcoming the strength-ductility tradeoff might be suitable way to address this challenge and meet increasing demands. Hence, this research focuses on the development of a new alloy concept capable of providing both high strength and good formability based on a novel design approach. This is tried via a crossover of beneficial material properties of already existing aluminum alloys or alloy classes by advanced alloy design. Based on the chosen design approach, an extensive study of available literature and thermodynamic calculations, a new class of alloys, termed crossover alloys, was created and intensively investigated and characterized. Experimental work included the development of an adequate processing concept, evaluation of hardening and forming capability in various conditions and in-depth investigations of the underlying microstructural mechanism. By applying the crossover approach and introducing adjusted amounts of precipitate-forming elements like Zn and Cu into usually non-heat-treatable AlMg alloys, it is possible to increase the alloys work hardenability in both soft and hard temper and to establish a yield strength level of up to 470 MPa. By fine-tuning the alloy composition and the heat treatment, hardening capability can be appropriately adjusted according to the intended application. The overall concept was proven valid to sufficiently address the strength-ductility tradeoff, but follow-up research is required to fully exploit the potential of the introduced crossover alloys. A major task will be addressing the challenges of industrial manufacturing the associated demands and constraints.

AB - Over the last decades the accelerated development of the traffic and transportation sector has caused significant alterations in the global climate due to ever rising emissions of CO2. Even though increasing political awareness and rising economic necessity have boosted research and development in this sectors, current technologies are still not capable of fully addressing this challenge. One way to substantially improve energy savings thus reduce the level of harmful emissions are significant optimizations in vehicle design which is strongly connected to the materials used. Light weighting by deploying low-density materials such as aluminum alloys to substitute high-density steel is a well-established approach to mitigate greenhouse emissions. Unfortunately, multiple operational demands and engineering criteria, in particular those promoting strength and ductility, limit the benefits of light weighting due to the restricted property portfolio of commercial aluminum alloys and requires the unbeneficial utilization of a multi-material-mix thus limiting the recyclability at the end of a product’s lifetime. Overcoming the strength-ductility tradeoff might be suitable way to address this challenge and meet increasing demands. Hence, this research focuses on the development of a new alloy concept capable of providing both high strength and good formability based on a novel design approach. This is tried via a crossover of beneficial material properties of already existing aluminum alloys or alloy classes by advanced alloy design. Based on the chosen design approach, an extensive study of available literature and thermodynamic calculations, a new class of alloys, termed crossover alloys, was created and intensively investigated and characterized. Experimental work included the development of an adequate processing concept, evaluation of hardening and forming capability in various conditions and in-depth investigations of the underlying microstructural mechanism. By applying the crossover approach and introducing adjusted amounts of precipitate-forming elements like Zn and Cu into usually non-heat-treatable AlMg alloys, it is possible to increase the alloys work hardenability in both soft and hard temper and to establish a yield strength level of up to 470 MPa. By fine-tuning the alloy composition and the heat treatment, hardening capability can be appropriately adjusted according to the intended application. The overall concept was proven valid to sufficiently address the strength-ductility tradeoff, but follow-up research is required to fully exploit the potential of the introduced crossover alloys. A major task will be addressing the challenges of industrial manufacturing the associated demands and constraints.

KW - aluminum

KW - alloys

KW - light metals

KW - development

KW - characterization

KW - Aluminium

KW - Legierungen

KW - Leichtmetalle

KW - Entwicklung

KW - Charakterisierung

M3 - Doctoral Thesis

ER -