As an aside, this is so much so the often used phrase "aerospace grade" whatever, especially on Kickstarters is just bull. There's nothing special in the materials, what they are concerned about is the ability to track every piece to where it comes from.
They're standard alloys with special process controls. "Aerospace grade" aluminum is commonly just 2024. "Aerospace grade" titanium is often 6Al-4V. What makes them special isn't the alloy at all but things like traceability, continuous monitoring and testing of critical material properties, and supply chain.
And you are sure about that? Because that would mean I purchased a lot of the wrong raw materials in my life, and if so I really, really should tell my collegues in engineering, procurement and quality control about it.
Not anymore, as it is quite a while I bought them. After all, it was just a P/N. Given that we had a full blown lab doing samples for all raw materials we bought to make sure tze alloy, heat treament and other properties were correct, yes, it definetly was different alloys. Quite a few actually.
Depends on the actual use case of course: requirements for safety critical parts are higher than for less critical parts, say part connecting rotor blades to the rotor head had higher requirements than the door handle (both which were actual titanium in one case, and please don't ask why a door handle would be titanium to begin with...).
Generally so, to come back to your question:
I remember three different titanium alloys with different heat treatment we used back then. And at least five different alumium alloys. The Titanium ones were primarily aerospace, and export controlled depending in which form you bought it. And one particular steel alloy, not aerospace specific but also export controlled because it was dual use.
I think I see what you're saying - however I'm not hearing anything indicating a different aerospace-specific material, but rather aerospace-specific process. The raw stock with certs has a different P/N than that without certs, but not it's not a different material. For instance, we might procure aluminum 7075, which has a published spec in the form of ASTM B209 (and several others, this is one I've seen called out in drawings commonly). 7075 is available in multiple different tempers - you can get 7075-O (not heat-treated), 7075-T6, 7075-T651, and a few other less commonly used ones. When used for aerospace, that material will generally come with a cert from an independent test lab showing that a specimen from the batch meets the yield strength, ultimate tensile strength, yield at rupture, composition, and other critical properties. At the end of the day, the piece of round bar or sheet is the same thing you'd purchase otherwise, but you've paid quite a bit extra to be SURE that it's exactly what you expect. The same applies to steel, titanium, nickel alloys like Inconel or Monel, tungsten, magnesium, and pretty much everything else I can think of.
Following procurement, we might do in-house testing before machining (composition with XRF, physical properties with a tensile tester), possibly our own heat treatment (e.g. 13-8PH, 15-5PH, 17-4PH are "precipitation hardening" steels, generally delivered soft), and surface treatment (passivation, conversion coating) before delivering a finished product. None of this is unique to aerospace either, although it's certainly unlikely you'd want to spend the money for it otherwise.
So yes, you procure a different item, possibly from a different supplier, but physically there's unlikely to be any difference in my experience. The exception I'm aware of would be electronic components, particularly semiconductors, which are manufactured using different processes for radiation hardening (e.g. sapphire substrate). Export control like ITAR/EAR aren't really about aerospace but rather restrictions imposed by the US Government.
Of course there is no "aerospace only" alloy. There are a whole bunch of specialized alloys that get primarily used in aerospace so, and those are a far cry from your average construction material alloys (those get used to, but pose their own kinds of challenges). That's the whole point. Also, P/N were internal, of course the supplier had different PNs, including or excluding certificates and such things.
And before some asks, no, those inventories, the ones with and without certificates and paper work, never get mixed. That they don't is actualy audited.
If go away from metalic materials, there is only a limited number of suppliers for aerospace grade carbon fibres: Torray and two others I can't remember the names. And those fibres actually are different from the non-aerospace ones in some cases, while in others they quite similar to the non-aerspace ones technically.
Overall I think we agree so. And yes, people tend to oversell the "aerspace grade" stuff. As they do with "mil-spec".
ITAR is a pain in the ass, on top of being a US government thing not limited to aerospace.
Surface treatment is tricky, as a special process (for QA purposes, those have rigorous standards) they take ages to get certified.
One of the first thing an old hand told me in my first days on the job, in aerospace, was: If you have a part, but have no paper work you can match against the part that tells you what it is, you can throw the part away. So, never loose documentation.
I took that to heart. Took a case of a switcheroo, mixing items that looked similar but aren't, to really drive the point home.
As an aside, this is so much so the often used phrase "aerospace grade" whatever, especially on Kickstarters is just bull. There's nothing special in the materials, what they are concerned about is the ability to track every piece to where it comes from.