On the potential of aluminum crossover alloys

For almost a century commercial aluminum alloys were developed and optimized for high performance in a specific and narrow range of application, which commonly coincides with their industrial classification. Overcoming the limitations associated with the modern lightweighting concept requires new alloy design strategies that offer an expanded property portfolio with a better trade-off between formability and achievable strength. The associated materials would be key to circumventing the need for a multi material mix that diminishes the recyclability of the final product. This review summarizes current knowledge about a new class of materials, “crossover alloys”, that combine advantageous properties normally limited to certain classes of commercial aluminum alloys. It focuses on the crossover alloys AlMg/AlCuMg (5xxx/2xxx) and AlMg/AlZnMg(Cu) (5xxx/7xxx). Recently available research data provides indications for superior formability with simultaneously high age-hardening potential, which may pave the way for broader industrial application in the foreseeable future. Because these new alloys exhibit Mg as their major constituent but are – in contrast to commercial AlMg alloys – age hardenable, they do not fit into the current alloy classification scheme. This review formalizes crossover alloys as a potential new aluminum alloy class which features an innovative alloy design methodology.