Alloy design principles for tomorrow's aluminium alloysThursday (07.11.2019) 11:45 - 12:05 Part of:
Aluminium industry is currently active on several fronts: the development of advanced alloys for the automotive and aerospace industries and of Additive Manufacturing (AM)-optimized Al-based alloys. Alloy designs principles are very different in each of these developments as the processing conditions differ from one application to another. Nevertheless, all these developments aim at improving properties of these alloys through microstructural optimization.
Automotive industry is more than ever in need of lightweight–and thus high strength–solutions. Continued development of advanced alloys for automotive is supported by microstructural engineering: equilibrium phase diagram calculations and precipitation computations coupled with laboratory prototyping. As a result, innovative alloy composition and processing conditions were developed for Al automotive body sheet alloys to compete with advanced high strength steels for structural parts:
Ultra high strength 6XXX alloys exploring high Cu-Si-Mg domain, where Q phase is the main strengthening precipitate.
High strength and formable 7XXX alloys achieved through adapted pre-tempering and processing technologies.
AM in metals is maturing rapidly, with particular focus on laser powder bed AM processes. Conventional high performance Al alloys present a number of drawbacks in laser powder bed AM, including solidification cracking, issues with volatile Zn in processing 7xxx alloys, porosity formation during solution heat treatment or distortion during quenching. Most work on Al for powder bed AM has focused on Al-Si alloys which have only moderate strength. However, alloy design rules and preferred alloy chemistries for AM can be totally different from conventional alloys: the fast cooling during laser processing leads to extremely fine, non-equilibrium microstructures which can bring component properties unachievable with conventional alloys. In this context, Constellium is developing new aluminum powder alloys for laser powder bed AM. Control of microstructure will remain key in allowing new Al systems to reach their full potential. Significant challenges remain in simulating the microstructures generated by the powder bed AM process, and in modelling the properties of the resulting components.
Alloy design principles for next generation Al alloys will be discussed in the light of microstructure-property relationships combined with processing-microstructure approaches.