I've always regarded Japanese alloy frames as being made of non heat treatable aluminium. It's the 'safest way' to proceed when working with them.
When the first alloy frames (of course, alloy swingarms appeared even earlier) came out - to the best of my dim dark memory, the GSXR400s (any Oz blokes remember Robbie Phillis' GSX1100 shoe horned into a GSXR400 chassis for the Swan Series? Talk about upspecing the engine!) were the first mass production alloy framed bikes to arrive in OZ - I wondered if /when we would see a lot of frame problems. But, giving thought to the major companies fear of liability, I thought that it would be done well/properly.
Time has proved that trusting naivety right. All things considered, I've seen bugger all problems with Japanese aluminium frames, even the early, small section GSXR1100 frames are still out there going well.
You will find on many frames different grades of alloy - even strange mixtures of heat treatable and non HT types. But , for the most part, they will be in, as much as possible, in the same series, eg - 7000.
A series of alloy , will have a multiplicity of grades within it, catering for forgings , castings, extrusions etc, etc. And for a wide variety of loads etc.
The major manufacturers will have proprietary alloy grades made for them - and metallurgists can create some amazing blends of alloys, in all sorts of non ferrous & ferrous metals.
There are alloys out there that even we who have made our living from fabrication and design would be stunned by.
7005 aluminium is THE workhorse material in Asia, it's used in the vast majority of applications, especially the cycling world. The big thing about it, and many non heat treatable alloys, are the savings in not having to go through the heat treatment process. It represents a massive saving in production costs - you just weld the sucker up, re-align the fabrication up if required, and it age hardens (actually, nearly all aluminium grades / series are age hardening, the extent of such being vast in range) back to it's original specs.
In my bicycle frame making, I have a lot of people coming to me to repair their frames. For the most part, I tell them no. Bicycle frames are made at such a level of minimalism, they are right on the edge of material limits at the upper level, so they definitely have a very finite life (aluminium in general has a very finite life, if it approaches it's design / materials limits, that is why MC frames are so substantial and so , relatively, heavy for what they are) and once such light gauge material starts cracking etc, you'll just keep on chasing other failures. I tell them, to thank the frame for not exploding, and hang it up as a souvenir. To often I've been at races, to only see blokes racing with dodgy repairs, or the same dodgily repaired frame sold onto someone else.
A fellow who'd bought a repaired frame, that failed and seriously hurt him, tried to sue me as the previous owner had told him it had been repaired by Bear Bikes - it didn't get to far as I certainly had not repaired the thing. Record keeping and proprietary ID'ing jobs is a good thing to have!
As for a formerly much touted individual heat treating his frames - well , I think, with his record that any claims he made would be in doubt by now. Mind you, I'm not aware of the extent of his claims of heat treatment, it could well have been him just glorifying artificial age hardening his frames, and not solution heat treating it ( do that with many aluminium alloys and you can count your days as numbered). A 7000 series frame should, if done carefully, not suffer by the heat levels / times needed to 'age' a section of 6061 put in as frame rails / inserts, if indeed, that was done at all.
Cryzsurfer , I think, posted his test results / opinions quite a long time ago, and has restated it recently. He has stated he works in heat treating / metallurgy, and I believe him. As I've said, I've always regarded Japanese frames as being made in non heat treatable alloys - it's the safest way to deal with them.
As for the bicycle tubing available - certainly , don't go there!, Way too thin for frame rail usage. Mind you, the materials ( specifically steels) and butting / profiles are leading edge.I'm currently awaiting some very expensive Reynolds 953 ( a very trick grade of SS) tubing for my XC and 4X frames, and am trying to get the same grade in straight gauge tubing for MC projects. Last night I was welding .2mm thick 853 tubing at the seat tube/seat stay junctions of an XC frame - that makes for high stress levels in this old, half blind, unsteady blokes mind. A triple scotch made me relaxed enough to fire up the Miller
And the precision fabrication levels / stds in top level bicycle frame manufacture make production motorcycle stds look pathetic. It can be very sobering to check the alignment of many MC frames............
