Date: Fri, 21 Mar 1997 23:09:39 -0500 (EST) From: JQUESTCOZY@aol.com Subject: COZY: 2024 question Hi all: Wicks sometimes substitutes 2024 T4 aluminum for T3. ie. in the main spar chapter 14 they sent T4 per their chapter breakdown. Anyhow, are these two inter changeable? What are the differences between T3 & T4? (heat treat?same strengh?) I also noticed that the 2024 T3 "bar stock" has a different look than the 2024T3 sheet. Is this from Alcad coating on sheet only? I made my spar hardpoints from 2024 T3 sheet that I cut to the 2 inch width vs.bar stock and would assume it's the same characteristics. Thanks John Wilemski chap.19 Date: Fri, 21 Mar 1997 22:58:49 -0800 From: berkut@loop.com Subject: Re: COZY: 2024 question >Hi all: > >Wicks sometimes substitutes 2024 T4 aluminum for T3. ie. in the main spar >chapter 14 they sent T4 per their chapter breakdown. Anyhow, are these two >inter changeable? What are the differences between T3 & T4? (heat >treat?same strengh?) Just the artificial ageing. Take T-3, let it sit around for a few years and it will become T-4. You're fine >I also noticed that the 2024 T3 "bar stock" has a different look than the >2024T3 sheet. Is this from Alcad coating on sheet only? I made my spar >hardpoints from 2024 T3 sheet that I cut to the 2 inch width vs.bar stock >and would assume it's the same characteristics. Alclad is a thin coating (almost a plating) of pure AL on the surface of an alloy. The pure aluminum corodes less than an alloy, that's the difference in look. Remember, while it's very nice to have the hardpoints in the spar bonded to the glass, the strength of the bolt attachment is depending on the aluminum acting as a washer, forcing the laminate into shear. If the bond failed entirely it wouldn't come apart. -- Czech Sikhs! Richard Riley "Heavier than air flying machines are impossible." Lord Kelvin, President, Royal Society, c 1895 See the Berkut at http://www.berkut.com Date: Wed, 12 Nov 1997 23:21:52 -0500 From: Ian Douglas Organization: WTC Subject: COZY: T3 and T4 What is the difference between T3 and T4 aluminum? It has been a LONG time since I took meteralogey (can't even spell it anymore!). I have a feeling that the attach pieces LWA4 and LWA6 in the centre spar and wings are T4 instead of T3 (I was just about to glass the shear web when I noticed that the pieces were cut out of the wrong material and I am guessing that the centre spar that came with this partially finished project also has T4 instead of T3. -- Ian D.S. Douglas MK0069 (possibly rebuilding a centre spar) From: Marc J. Zeitlin Subject: COZY: T3 and T4 (fwd) Date: Thu, 13 Nov 97 9:01:00 EST Ian D.S. Douglas writes: >What is the difference between T3 and T4 aluminum? >MK0069 (possibly rebuilding a centre spar) The "T" designation on the metal indicates the heat treatment. According to "Mark's Standard Handbook for Mechanical Engineers", here are the differences between 2024-T3 and 2024-T4: Brinell Yield Tensile Elongation Endurance Hardness 1000 psi 1000 psi % 1000 psi -------- -------- -------- ---------- --------- T3 120 50 70 18 20 T4 120 47 68 20 20 As you can see, the differences are marginal, at best. The T4 is not QUITE as strong, but is slightly more ductile. They both have the same endurance (fatigue) limit and hardness. Given that the wing attach fittings (the LWA's) are there to take the bolt load and spread it into the shear web, that the whole wing structure has a large safety margin and that (I would assume) that the wing structure was originally designed using the fatigue (endurance) limit as the limiting stress value, I wouldn't worry - you've got practically identical materials here. I would, however, give both Nat and Burt R. (Mike Melvill) a call and ask their opinion, since I'm only ASSUMING that these things are the case, since it's what I would have done had I designed the wing/center spar structure. -- Marc J. Zeitlin Email: marcz@an.hp.com From: "Fred I. Mahan" Subject: Re: COZY: T3 and T4 (fwd) Date: Thu, 13 Nov 1997 09:27:42 -0500 > Ian D.S. Douglas writes: > > >What is the difference between T3 and T4 aluminum? > Mark replies: > > As you can see, the differences are marginal, at best. The T4 is not > QUITE as strong, but is slightly more ductile. They both have the same > endurance (fatigue) limit and hardness. As a practical matter, you may have purchased 2024-T3 and now have T4. The ACS catalog of T3 is "solution heat treated, the cold worked." Some have also been sent T351, which is "solution heat treated, stress-relieved stretched, then cold worked." For T4, it says, "solution heat treated, then naturally aged." So, you can buy T3, let it set around for ?? years, and it has become T4. This was discussed a while back on one of the newsgroups or on the Canard Aviators list. If I can find the message I'll post it. Fred in Florida Date: Thu, 13 Nov 1997 12:02:25 -0500 From: bil kleb Organization: NASA Langley Research Center Subject: Re: COZY: T3 and T4 Ian Douglas wrote: > > What is the difference between T3 and T4 aluminum? part of the temper designations for aluminum alloys according to american national standard h35, 1-1972, reaffirmed jan 1989: T3 solution heat-treated and then cold-worked: applies to products which are cold worked to improve strength, or in which the effect of cold work in flattening or straightening is recognized in applicable specifications. T4 solution heat-treated and naturally aged to a substantially stable condition: applies to products which are not cold worked after solution heat-treatment, or in which the effect of cold work in flattening or straightening may not be recognized in applicable standards. additional digits: T_51 stress-relieved by stretching: applies to products which are stress-relieved by stretching the following amounts after solution heat-treatment: plate 1.5-3.0% permanent set rod, bar, and shapes 1.0-3.0% permanent set drawn tube 0.5-3.0% permanent set additional notes gathered from the 24th ed. of the machinery's handbook: cold working is also know as strain-hardening or work-hardening. for the non-heatreatable aluminum alloys, this is the only method available for strengthening. for heat-treatable alloys, cold working improves the strength gained by the initial heat/quenching cycle and further improves upon further aging (aka precipitation hardening) which occurs at or above room temperature. sometimes, T4 rivets are stored at freezing temperatures to prevent natural aging in order to preserve workability. -- bil From: "norm & monda" Subject: Re: COZY: T3 and T4 Date: Thu, 13 Nov 1997 15:14:37 -0500 t3 t4 who cares, its just a little different on the hardness and way it was hardened, this isnt the space shuttle afterall. i couldnt get t3 in the sizes when i needed it so allmost all of mine is t4 norm