If you spotted the code AMS 5663 on some technical drawings, you might assume it’s another one of those blazing fast 5G mobile standards. So I thought, anyway. Turns out, I’d be wrong. It’s actually a rather brilliant new superalloy that’s been specially formulated for aerospace bits and bobs that experience serious stress – like rotating propellor bits or payload fasteners. In other words, high-performance kit that really can’t afford to fail at cruising altitude.
Now you’re probably wondering – what makes this alloy so darn magical? Well firstly, its precise chemical make-up. We’re talking 3.3% boron, 0.006% carbon, 0.5% iron, 0.4% silicon and 0.1% copper. The rest being nickel, aside from trace elements here and there. This tuned nickel-based combination results in substantially stronger corrosion resistance and higher yield strength compared to old alloys. We’re talking over 150 ksi yield and more than 200 ksi tensile strengths in strict thermal conditions. All whilst meeting strict rules for ductility, fracture toughness and fatigue thresholds that alloys for flight must achieve nowadays.
The mechanical wizardry stems from AMS 5663’s microstructure as well. See, its distribution of gamma prime and gamma double prime particles spread amongst the nickel foundation hinders deformation when physical loads are applied. Furthermore, the aluminium and titanium percentages change up the grain boundaries so they obstruct cracks from spreading – either when initiated at the surface or internally.
What’s it all mean? Next-level endurance for the demands of modern aerospace hardware…without being heavyweight like old alloys. So improved fuel efficiency, less emissions, happier accountants – everybody wins. Well, except for metallurgists having to memorise yet another intricate alloy designation! But progress never sleeps, I suppose.
Now this is all jolly interesting from a geeky metals perspective. But how exactly does an alloy like AMS 5663 make it from lab benches onto actual flight assemblies? Turns out, quite an arduous journey indeed. Extensive controlled testing first validates AMS 5663 specimens meet not only chemical composition requirements, but also exhibit sufficiently high tensile, yield, fracture and crack growth measurements across a spectrum of thermal and mechanical conditions. Engineers bang, bend, dent, heat, freeze and abuse those samples in every way possible – simulating anything aircraft alloys might endure from the cruise to the hangar during routine maintenance.
Only once a new alloy passes this battery of qualification assessments with flying colours do aerospace manufacturers finally weave it into their approved material indexes. From there, it might find use in precision cast engine components or become precision-milled fasteners holding vital bits together. Usage slowly ramps up over successive generations of aircraft too, as design engineers gain confidence with incorporating newfangled alloys like AMS 5663. Of course airplane models must undergo their own arduous multi-year certifications as well – so no quick routes here! But eventually, today’s shiny new alloy could end up almost ubiquitous 20 years hence.