bending aluminum?

[Guest Nogbad]

Nogbad's annealing to soften previously heat treated material sounds reasonable, but the water quenching afterwards gives me pause. Many alloys will precipitation harden with such treatment. They will get harder, obtain higher yield strengths with with lower ductility with such fast quenching.

 

The heat treatment I suggest is to remove the effects of work (or strain) hardening. This method also anneals precipitation hardening alloys such as the 4000 series. When the alloy is heated, recrystallisation removes the tangles of dislocations resulting from previous plastic strain, reducing the yield stress and rendering the alloy soft once more. Once recrystallisation has occurred, with commercial aluminium it is unimportant whether you let it cool slowly or quench it.

 

In the case of a precipitation hardening alloy, it is necessary to hold the material at the high temperature for sufficient time as to re-dissolve the precipitate in the matrix. Once this has occurred, the metal should be rapidly quenched. This leaves the alloy soft with all the constituents in solid solution. Subsequent hardening is then achieved by an aging treatment where the alloy is heated to a lower temperature for a time sufficient to precipitate the hardening phase in the matrix. If the alloy is held at too high a temperature or for too long a time the precipitates will coarsen too much to be effective and the alloy will soften. Clearly without quenching some re-precipitation will occur and the material will neither be as soft as possible, nor as susceptible to controlled aging later.

 

With steels, the hardening process is entirely different, in that it is based on the conversion of the face centred cubic high temperature "austenite" phase into the body centred tetragonal "martensite" phase. The tetragonality achieved being proportional to the carbon content. The internal crystallographic strain is responsible for the hardness of quenched steel. There are however precipitation hardenable steels (e.g. maraging steel) and various types that exhibit a combination of various mechanisms.

 

You are therefore incorrect when you say that a material could precipitation harden on quenching. Precipitation hardening is a time and temperature dependent diffusion driven process where the precipitating constituent first forms areas of slightly elevated concentration in the matrix known as Guinier-Preston zones, and then forms fine second phase particles. Optimum hardness occurs where these are allowed to reach a size similar to the dislocation spacing. Further coarsening causes harness to be lost again. Note however that although over-aged material will become softer, it will lose considerable ductility due to the coarse precipitate.

[Ryland3210]

John, the anodized extruded aluminum stock WS is speaking about is very soft aluminum. Its ductility is a requirement for all extrusions and it is fairly malleable. T6 (6061), on the other hand, is aircraft grade alloy, brittle and hard, has a tensile strength of 42,000 psi, yield strength of 35,000 psi, is neither ductile, as you mentioned, nor at all malleable. Standard stock aluminum such as extrusion stock at Home Depot will not have properties anything close to T6.

 

Properties of steel alloys with regard to heat treating methods are entirely different than that of aluminum alloys, and I would not expect those used in making a steel screw driver, (which I have also done) to apply to any alloy of aluminum.

 

BTW, the air filter bracket I sent you gratis, postage paid, at your request many months ago (photo below) was made of the same anodized extruded aluminum strap we're speaking of, and is the stuff you get from Home Depot. It has strong, 90-degree bends with no loss of strength. Like I said above, I use this aluminum strap for lots of things. Never heard a single word back from you, John -- not as much as an acknowledgement that you received it. I guess you never received it, but then, since you were expecting it, after all the coordination on shipment -- not a word??

 

I was certain I had thanked you via a personal message for your generosity, especially since I had offered to pay for it. Please accept my abject apologies if you didn't receive my thank you message before.

 

I was also impressed with the meticulous care you took in packing it to protect it during shipment. The situation is that it took my quite some time to acquire the mufflers I was seeking. The reason that is relevant is that I did not want to run the bike with either of those changes without having it dyno tuned and remapped. My plan was to get that done and report back to you. However, John Tavolacci, the local Dyno Jet tech had an accident, and was out of commission for several more weeks. I'm just now getting to the point where I can get that done, but the weather got in the way, then the Holidays.

 

I hope you know me well enough to know I'm not one to ignore the kindness and generosity of others. FWIW a personal message is more likely to get my notice, since I sporadically monitor threads these days.

 

Thanks for the info. on the aluminum sold by Home Depot.

 

PS, I still plan to return the clamp to you (postage prepaid) as soon as I can locate an original airbox cover to carve up. FWIW, I have been waiting to hear from a mutual acquaintance that told me many weeks ago he would get one from his boneyard. Let me know if you want it back post haste, and I'll take it off my bike and send it back.

[Ryland3210]

The heat treatment I suggest is to remove the effects of work (or strain) hardening. This method also anneals precipitation hardening alloys such as the 4000 series. When the alloy is heated, recrystallisation removes the tangles of dislocations resulting from previous plastic strain, reducing the yield stress and rendering the alloy soft once more. Once recrystallisation has occurred, with commercial aluminium it is unimportant whether you let it cool slowly or quench it.

 

In the case of a precipitation hardening alloy, it is necessary to hold the material at the high temperature for sufficient time as to re-dissolve the precipitate in the matrix. Once this has occurred, the metal should be rapidly quenched. This leaves the alloy soft with all the constituents in solid solution. Subsequent hardening is then achieved by an aging treatment where the alloy is heated to a lower temperature for a time sufficient to precipitate the hardening phase in the matrix. If the alloy is held at too high a temperature or for too long a time the precipitates will coarsen too much to be effective and the alloy will soften. Clearly without quenching some re-precipitation will occur and the material will neither be as soft as possible, nor as susceptible to controlled aging later.

 

With steels, the hardening process is entirely different, in that it is based on the conversion of the face centred cubic high temperature "austenite" phase into the body centred tetragonal "martensite" phase. The tetragonality achieved being proportional to the carbon content. The internal crystallographic strain is responsible for the hardness of quenched steel. There are however precipitation hardenable steels (e.g. maraging steel) and various types that exhibit a combination of various mechanisms.

 

You are therefore incorrect when you say that a material could precipitation harden on quenching. Precipitation hardening is a time and temperature dependent diffusion driven process where the precipitating constituent first forms areas of slightly elevated concentration in the matrix known as Guinier-Preston zones, and then forms fine second phase particles. Optimum hardness occurs where these are allowed to reach a size similar to the dislocation spacing. Further coarsening causes harness to be lost again. Note however that although over-aged material will become softer, it will lose considerable ductility due to the coarse precipitate.

 

Thanks for taking the time to write this thorough review. I don't see where I was incorrect, however, in my very brief comment which left out the various heat treatment steps which you included. It was not an explicit statement that precipitation hardening was caused by the quenching stage.

[dlaing]

Anneal the aluminium as follows to render it soft for further bending.

 

Heat gradually with a gas torch to about 400°C. A good guide to the correct temperature is that a matchstick wiped across the surface smokes but does not ignite, leaving a whitish line on the ally.

 

After you get it to this temperature, quench into a bucket of cold water.

 

The material will now be soft and can be further bent.

http://www.suppliersonline.com/propertypages/2014.asp

" Hardening is accomplished by a precipitation heat treatment at 935 F followed by water quench. This produces T4 temper."

I am not sure if the above statement contradicts your statement, but it seems to. I am sure there could be an explanation for both statements being true.

[Guest ratchethack]

PS, I still plan to return the clamp to you (postage prepaid) as soon as I can locate an original airbox cover to carve up. FWIW, I have been waiting to hear from a mutual acquaintance that told me many weeks ago he would get one from his boneyard. Let me know if you want it back post haste, and I'll take it off my bike and send it back.

Glad to at least know it arrived, John, though it seems it won't meet your needs after all. No big hurry on the return, though I would appreciate getting it back if you're not going to use it.

[Guest Nogbad]

http://www.suppliersonline.com/propertypages/2014.asp

" Hardening is accomplished by a precipitation heat treatment at 935 F followed by water quench. This produces T4 temper."

I am not sure if the above statement contradicts your statement, but it seems to. I am sure there could be an explanation for both statements being true.

 

It depends on the alloy. Plain aluminium won't age, the above is for Dural type (Al 4% Cu and similar) although there are now many types and they all require different temperatures and times to get the properties you might want. There is no contradiction there. The scheme is always a high temperature solution treatment followed by quenching, leaving the alloy soft for forming, followed by a lower temperature aging step. The final quench is applied simply to give a sharp cutoff to the aging step, important with heavy sections or forgings that have thin and thick parts that could cool at widely differing rates if naturally cooled.

[dlaing]

It depends on the alloy. Plain aluminium won't age, the above is for Dural type (Al 4% Cu and similar) although there are now many types and they all require different temperatures and times to get the properties you might want. There is no contradiction there. The scheme is always a high temperature solution treatment followed by quenching, leaving the alloy soft for forming, followed by a lower temperature aging step. The final quench is applied simply to give a sharp cutoff to the aging step, important with heavy sections or forgings that have thin and thick parts that could cool at widely differing rates if naturally cooled.

The site I posted has a process for annealing that involves no quenching and slow cooling and a process for hardening that involves quenching, and controlled aging only if a temper other than T4 is desired.

I think Ryland was completely correct when he said:

Nogbad's annealing to soften previously heat treated material sounds reasonable, but the water quenching afterwards gives me pause. Many alloys will precipitation harden with such treatment. They will get harder, obtain higher yield strengths with with lower ductility with such fast quenching.

The result of your recommended quenching easily could be T4, right?

While if one did not quench, there is a greater chance a mysterious alloy would be more bendable after heating, right?

[Guest george in vancouver]

The site I posted has a process for annealing that involves no quenching and slow cooling and a process for hardening that involves quenching, and controlled aging only if a temper other than T4 is desired.

I think Ryland was completely correct when he said:

 

The result of your recommended quenching easily could be T4, right?

While if one did not quench, there is a greater chance a mysterious alloy would be more bendable after heating, right?

 

These Tinman Tech articles go over this. On a workshop level detail, it's about as comprehensive as you need. Their videos are great. Get yourself some aluminum sheet and start bashing!

[Guest Nogbad]

No, the safest route if you want maximum workability is to quench after holding at a suitable time at the solution treatment temperature. Once you have taken all the second phase constituent at room temperature into the solid solution single phase state at elevated temperature the only way to keep it there is to quench rapidly forming a supersaturated solid solution. This represents the most ductile state for precipitation hardenable alloys but not necessarily the softest. An over aged alloy may in fact be softer, but ductility will be impaired.

 

Don't get mixed up between quench hardening alloys e.g. carbon steel, and precipitation hardening alloys. The precipitate that gives the hardening action is a second phase formed by partly bringing the quenched state to toward the 2 phase equilibrium state. The precipitates both directly pin the slip planes and by creating lattice stresses raise the energy needed to move dislocations.

 

To cause precipitation hardening to occur, reheating is needed for a time suitable to allow for the formation of the second phase within the matrix. Precipitation therefore would be more likely to occur with a slow cool than with a fast cool. Obviously if the mysterious alloy you refer to underwent an allotropic transformation like steel, then it might indeed get harder, but this wouldn't be precipitation hardening.

 

Honestly Dave, are you just looking for an argument anywhere just because you don't like my politics?

[dlaing]

These Tinman Tech articles go over this. On a workshop level detail, it's about as comprehensive as you need. Their videos are great. Get yourself some aluminum sheet and start bashing!

Thanks!

It makes me want to replace all that plastic!!!

[Guest george in vancouver]

Thanks!

It makes me want to replace all that plastic!!!

 

Since you're down in that zone, you could do one of their workshop courses. Looks like big-ass fun. Did you check out some of the fairings, wheel pants, etc. those guys are bashing out? Beautiful ....................

 

I won't discount the value of the metallurgical level aspect, but for us down here in the shop, your learning cure is proportional to the size of the discarded / scrap pile & exclamations of "well ............. THAT is surely not the way to do it!" (well ............ up to a point anyway).

 

Will post a picture of a Magni fairing / headlight mounting rig that's the focus in the shop at the moment.

 

G

 

wa-la:

 

 

 

 

More beating and grinding today:

 

 

 

[dlaing]

Hi George,

That bracket looks nice!

Show us more as it progresses!

What are you going to do about the acrylic/polycarbonate screen?

[Guest george in vancouver]

Hi George,

That bracket looks nice!

Show us more as it progresses!

What are you going to do about the acrylic/polycarbonate screen?

 

Got it from Gustafson Plastics per Air Tech's recommendation. Seems like a decent piece.

 

More work on the fairing mount-up tomorrow.

[Guest NotRight]

Hey thumbs up to everyone on the metallurgy discussions. Generally on the mark. So now I wonder why I spent so many years studying metallurgy when its quite apparent that a person doesn't have to be obsessed, in debt with student loans, eyes shot from hours of microscope work, stunted charm from years of female free labs, likely poisoned from heavy metals and noxious fumes. That lung full of sodium gas I inhaled modifying alloys in the furnace and excema [sic] skin from sand binder compounds..........

 

Well it was fun at the time

 

Since we have some knowledgeable folks here with actual practial hands on skills let me ask you:

 

I developed and patented an aluminum casting alloy that had a novel feature in the heat treatment..... It does not need to be quenched after solutionzing. It MUST be solutionized and then artificially aged to be stable but you don't need to quench it between. In fact you could pull it out and stick it in sand to cool with little reduction in properties. The stale air cooled samples actually had the same properties as quenched in water/coolant.

 

Its only useful up to about 170 celcius for a component above that the properties fall off like 356.

 

I was returned the rights to the patent as the company went out of business.

 

Thoughts were it could be useful alternative for parts that warp or crack from traditional quenching in liquids such as wheels.

 

Its very flexible in that you can monkey with the silicon etc for different casting processes and flowability {a made up jargon word} in the die or mold.

 

I haven't had the time to pursue marketing it but that may change as I'm probably going to be downsized soon. I"m not in the metallurgy field these days but do you think it has potential? Or is skipping a quench operation not that helpful in practice?

[dlaing]

Honestly Dave, are you just looking for an argument anywhere just because you don't like my politics?

No, I do my best to keep the politics separate from the Guzzi related.

I suspect you are the one having trouble separating your fellow members from their politics.