Re: What Is Alloy?

Agent Smith wrote:
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Agent Smith wrote:
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Agent Smith wrote:
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Agent Smith wrote:
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Agent Smith wrote:
Does anybody know the name (or names) of the famous alloy from
which high- end racing components are made? :] Whenever I see
it referred to in books and articles, it is just called
"alloy," but apparently there's a whole branch of engineering
that's embodied in that single word, and writers gloss over the
whole subject when they say that.
Alloys are chosen or created with the intention to reliably fit
the function that engineers planned for in design. My guess is
the word alloy is used as representing a variety of alloys
suitable for a given design/application. Example: valves in a
high performance engine, be the valve stems hollow or solid, may
be made from 6-4 titanium (heat treated to 160KSI), while domed
piston heads may be made from 6061 aluminum; piston head pins
may be made from 7075 aluminum, assembled on connecting rods
which may be forged from 6-6 titanium (heat treated to 180KSI).
Various stainless steel and/or titanium parts may be made from
sintered stainless steel or titanium, where loads are low, below
the limits of sintered material yield. Then there's ceramics
...... (shrug)

I supposed you've already done an Internet search? I'll guess
again and say if you've done a search, you may have found alloys
having proprietary designations.
Until you said "7075," I didn't have a keyword to search for, but
I googled it last night, and now I've got the details. I would
have thought that it was alloyed with nickel, but it turns out to
be zinc. Compared to steel, 20+ KSI yield stresses are pretty pathetic,
but I guess that it's sufficient for the loads a component is likely to
experience in bicycling. I wonder who Campagnolo's suppliers
are, for that stuff, and who forges it.
Nickel is not a good alloying agent with aluminum.
Do you know why? :]
I can't recall the exact reason but I do recall meeting with metallurgists working for Allegheny saying their macro's showed poor
grain structure. I don't know, perhaps never did know, the alloy
blend they tested. That was back in the early 60's when titanium
sponge was gaining popularity. The industrial titanium alloy widely
was (and perhaps still is) 6Al-4V titanium heat treated to 160Ksi
-180Ksi Ultimate, with 95Ksi min shear. 6Al-6V Titanium can be heat
treated to 180Ksi min but its elasticity is lousy.

In this context, do Al & V stand for what I think they stand for?

Al = Aluminum

V = Vanadium

I thought that titanium alloys were steels.

(cough - cough ... gulp)

No, a titanium alloy is a titanium alloy. In a titanium alloy, titanium sponge is the principle material. Steel alloys are mostly iron and carbon with iron being the principle material. Titanium alloys, like steel alloys can be sintered if investment castings are to be made. When attending a school to learn metallurgy, the Iron-Iron theory is the first thing that must be learned. If you don't learn that, pass on learning metallurgy.

There's no carbon added to a titanium alloy and I'll guess if there is iron added it must be extremely low. Might be somewhere between 0.1% to 1.0%; that's a guess. If iron is added (of some quantity), it surely will affect the titanium alloy ductility properties, which is not normally good in airframe/missiles/space hardware. In such program use, I don't know where this type alloy would be used 'cause I'll bet its not only the fatigue properties are a joke, the material would also be very brittle. Might not be able to even roll-thread the material at room temperature.

As it is now, Titanium with just 6% vanadium, heat treated to 180Ksi-200Ksi does not have much elasticity but it might be used where compression loads are high. As an example: Take two 1/4 dia. rods, one 6-6 titanium and one 6-4 titanium. place the 6-6 titanium in a machinists vise and try to bend it. It will probably bend about 20 to 30 degrees then break, but the break will start at the elongation side of the rod. Do the same thing to 6-4 titanium heat treated to 160Ksi to 180Ksi (95 Ksi shear min.) and you'll bend that material to a full 90 degrees, with no breaks or cracks showing on the elongation or the compression sides of the titanium rod. However, neither alloy is good at elevated temperatures. To use titanium at elevated temperatures, remove vanadium and use tin (with magnesium, etc. etc.) and titanium could be used at something like 600 degrees F.; but you lose much (probably too much) of the room temperature mechanical properties that are inherent with 6-4 and 6-6 titanium alloys.

In the design engineering field, compositions of alloys are not memorized; there are tomes of published material that are commonly used by engineers, should they be interested in knowing such things. Normally, interested engineers would be metallurgists and quality control engineers, who would be responsible for making test specimens, over-viewing specimen testing, and following publication data, that board/designer (and ahem, program managers) engineers would use such as reference material. Design engineers would be over-viewing large assemblies undergoing fatigue testing or testing assemblies to be used in space vacuum. Life-cycle or seal capability is what they would want to know.

Aside:

Hey Agent, have to tell you I'm retired. Left the airframe/missiles/space business about 17 years ago. I'm no longer a designer, nor a manager of special programs, or a member of a team working on special programs. The information you're getting from me is from my memory banks (which I hope has its file draws and folders on open). I'm not interested in regurgitating what I left behind me so long ago. In fact, I actually like being retired. In effect, I'm probably technically obsolete by now. I haven't a clue as to what the mills are turning out and don't want to know. I once raised an eyebrow when learning cadmium could be bonded to glass. (Pssst, it's done in a vacuum chamber.) Of course you know Cadmium is only a solid in earths atmosphere.

I just thought of something. The only published tome I have seen that's larger than Mil-HDBK-5, is the material HDBK published by NASA. Lay that sucker on your chair and instantly you'll become a big-big man.

You would be wise to get in contact with someone who is still in the business and is technically up to date.


.

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  • Re: What Is Alloy?
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