# Why dont we see many Magnesium parts



## TheRedMantra (Jan 12, 2004)

Why dont any of the big companies use magneisum that much? Avid used to. There are the vuelta mags but those are not really production brakes. Some stems are magnesium. Some companies make magnesium frames. Now that I think about it bontrager makes mag barends. Why dont many companies use it? Is it hard to work with? Burn too easily? Couldnt one make very light parts with it like seatposts or rigid forks?


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## bike_freak (Dec 24, 2003)

TheRedMantra said:


> Why dont any of the big companies use magneisum that much? Avid used to. There are the vuelta mags but those are not really production brakes. Some stems are magnesium. Some companies make magnesium frames. Now that I think about it bontrager makes mag barends. Why dont many companies use it? Is it hard to work with? Burn too easily? Couldnt one make very light parts with it like seatposts or rigid forks?


 Aren't alot of Fork Lowers made out of magnesium? Also I know a couple of seat rails that are magnesium. I'm guessing the main reason is that there must be better materials around, I might be wrong, but when they use magnesium lowers on forks, it's usually cheap forks.
Then again, I have no clue....


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## TheRedMantra (Jan 12, 2004)

I know about fork lowers but I was talking about parts like seatposts or cranks, not things that you dont really upgrade ( some people do though - nino).


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## Disaster (Jan 15, 2004)

*Magnesium has it's uses but it isn't perfect.*

Magnesium is much more prone to corrosion than aluminum or titanium. Titanium really kicks but when it comes to corrosion resistance.

Magnesium is very light, casts great and machines great, however it isn't as strong as some of the forged, drawn and heat treated aluminums and titaniums.

Magnesium does not have as high a fatique strength as the better aluminum alloys or titanium.

Magnesium doesn't weld well...it's strength lies in how close it can be cast to it's final shape...very little maching is required with magnesium alloys.

Complex, thin walled designs are where magnesium really shines, like deraileur castings or shift housings. However, if strength isn't an issue with these parts, plastic will be chosen because it is so much cheaper.

Danny


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## eric (Jan 22, 2004)

*Agree there*

Also, few corrections:

1. Magnesium frames aren't actually magnesium - just like Scandium frames aren't make from Scandium. They just have a slightly elevated percentage of magnesium in the aluminium alloy. Whatever Merida says.

2. Magnesium isn't used for saddle rails. The Mn on the rails indicated use of Manganese, which is a different material than magnesium (Mg). It's commonly used in steel alloys.


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## DeeEight (Jan 13, 2004)

*A couple Bzzzzt Wrongs !!! and thanks for playing...*

Eric :

1. Magnesium frames ARE made from a magnesium alloy. Yes that means the primary element of the base alloy is magnesium. It is NOT the same as aluminium alloys that have magnesium added to them in the alloy mix. There are quite a few grades of structural magnesium. suitable for bicycle frames including WELDABLE ones. Merida uses 'em and Lodestar/MgLitech (same company) used 'em. Also Kirk Precision was casting magnesium frames 2 decades ago.

2. The so called manganese saddle rails are actually steel alloys where the primary additive to the alloy is manganese. Manganese steel alloys were quite commonly used for bicycle frame tubing a couple decades ago, before chromoly alloys became popular. Classic Reynolds 531 and Tange Mangaloy are examples of that.

Disaster :

The structural grades of magnesium alloys, both the castable ones and the weldable ones compare quite closely to 6061T6 and 7005T6 aluminium in terms of strengths, and this is quite suitable to making frames from. The reason more parts aren't made from it is a question of lack of demand.

Magnesium doesn't need a high fatigue strength since unlike all aluminium alloys outside the 5xxx series, it has a defineable fatigue limit. Meaning a designer can safely predict WHEN a magnesium part will fail and design it accordingly. Its not neccessarily to add on lots of extra material as with aluminium in order to keep the stiffness up and thus limit the number of fatigue cycles it endures.

There are weldable magnesium alloys that weld just as easily as some aluminium alloys do.


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## Motivated (Jan 13, 2004)

*Numbers*



DeeEight said:


> Eric :
> 
> 1. Magnesium frames ARE made from a magnesium alloy. Yes that means the primary element of the base alloy is magnesium. It is NOT the same as aluminium alloys that have magnesium added to them in the alloy mix. There are quite a few grades of structural magnesium. suitable for bicycle frames including WELDABLE ones. Merida uses 'em and Lodestar/MgLitech (same company) used 'em. Also Kirk Precision was casting magnesium frames 2 decades ago.
> 
> ...


The strength of structural magnesium alloys are significantly less than 6061 and 7075. Typical yield strenght for these aluminums is 40,000 psi. Maximum for magnesium is 22,000. DeeEight, if you know of a mg alloy that closely matches that of 6061 please post about it.

Stiffness (Young's Modulus) of aluminum alloys on bikes is also significantly higher than magnesium alloys. Typical for aluminums is 10,000 ksi. Maximum for magnesium alloys is 6600 ksi.

Of course magnesium alloys are less dense (.066 lb/in^3 vs. .098 lb/in^3) and that is the main reason it is used in aerospace (second is maybe damping characteristics) but typical bike aluminums have better strength to weight and stiffness to weight ratios.

One significant reason Mg alloys are not used for frames is that it is extremely difficult to make tubing, much less the fancy butted, profiled and shaped tubes on modern bikes. Yes Merida does make a Mg alloy frame but look at it - all the tubes are basically straight. There is clearly demand in the high-end niche as customers spend >$2,000 on frame, so the reason magnesium isn't employed is lack of performance relative to aluminum, titanium and graphite composite. I think there are other parts which are good candidates for magnesium: crankset, derailleurs, brake calipers and fork tubes.

A friend of mine raced a magnesuim frame single speed. I was very impressed until the frame broke, however it was replaced. He refused to reveal who made it. It was not a Merida.


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## Ultra Magnus (Jan 13, 2004)

You have one inaccuracy in your post regarding the strength of magnesium alloys. There are a few alloys that exceed the tensile strengths of 6061. Check out matweb.com. The have a HUGE database of materials and their properties. You can also do property searches. Do one for magnesium alloys with a minimum yeild tensile strengths of 39,000 psi and see how many alloys come up. I was very surprised. They may cost an arm and a leg, though! Also, the shear modulous of magnesium is lower than aluminum too. 

I actually found two aluminum alloys that are FAR stronger than 7075. 7075 has a tensile strength in the neighborhood of 70k psi, and I think it was like 7001 Al that was greater than 90k psi. That site makes for some very interesting browsing..


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## Motivated (Jan 13, 2004)

*Thanks*



bmadau said:


> You have one inaccuracy in your post regarding the strength of magnesium alloys. There are a few alloys that exceed the tensile strengths of 6061. Check out matweb.com. The have a HUGE database of materials and their properties. You can also do property searches. Do one for magnesium alloys with a minimum yeild tensile strengths of 39,000 psi and see how many alloys come up. I was very surprised. They may cost an arm and a leg, though! Also, the shear modulous of magnesium is lower than aluminum too.
> 
> I actually found two aluminum alloys that are FAR stronger than 7075. 7075 has a tensile strength in the neighborhood of 70k psi, and I think it was like 7001 Al that was greater than 90k psi. That site makes for some very interesting browsing..


My materials handbook data was a bit outdated. So there are magnesiums that approach 40,000 psi yield strengh, which I consider typical for aluminum. I was aware that some aluminums (i.e. 7075) have higher strengths, but have never seen anything up near 90,000 psi.

Despite the advances in magnesium it remains true (based on searching matweb) that aluminum still poseses slightly better stiffness to weight ratio:
6061 T6: 10,000 ksi / .098 lb/in^3 = 102E6 (some aluminums have stiffness ~ 11,000 ksi)
Mg alloy: 6530 ksi / .066 lb/in^3 = 99E6 (this is the maximum stiffness I've seen for Mg alloy)

But it is easier to design and machine parts with lower density due to the thicker sections, so it makes sense to use magnesium alloy for parts like crankarms.


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## DeeEight (Jan 13, 2004)

Motivated said:


> The strength of structural magnesium alloys are significantly less than 6061 and 7075. Typical yield strenght for these aluminums is 40,000 psi. Maximum for magnesium is 22,000. DeeEight, if you know of a mg alloy that closely matches that of 6061 please post about it.


First of all I said 7005 NOT 7075 !!!

Secondly I could post a couple dozen Mg alloys that exceed 40ksi yeild strength. That's one of the reasons why Mg is used in fork leg castings (which includes the fork brace btw). Its replaced 6061T6 which was the previous choice alloy for most fork makers doing sliders and braces.



> Stiffness (Young's Modulus) of aluminum alloys on bikes is also significantly higher than magnesium alloys. Typical for aluminums is 10,000 ksi. Maximum for magnesium alloys is 6600 ksi.


Stiffness isn't a problem. As I said, Magnesium alloys don''t have the problem of an undefined fatigue limit like aluminium alloys do (which is why Al parts and frames are overbuilt if they're items subject to repeated flexing like a seatpost, stem, or frame). Magnesium frames are specifically popular because they ride better than aluminium frames. The lower density is just a bonus. Magnesium also dampes vibrations better than
aluminium. This is a property of the material. This is why Easton makes magnesium stems. And since they rate those stems for DH riding, strength isn't something they're lacking in.



> One significant reason Mg alloys are not used for frames is that it is extremely difficult to make tubing, much less the fancy butted, profiled and shaped tubes on modern bikes.


No its not. You can easily extrude the tubes into different shapes.

http://www.merida.com/s0_global/main_control.php?group0=tech&group1=shotgun


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## Ultra Magnus (Jan 13, 2004)

Check out these:

http://matweb.com/search/SpecificMaterial.asp?bassnum=MA9WELD8
http://matweb.com/search/SpecificMaterial.asp?bassnum=MA7001T6

I don't think these alloys are truly comercially available, so to design parts out of this stuff would probably be a bit pricey.


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## novice (Jan 14, 2004)

DeeEight, why do you keep talking about stiffness and fatigue?

While you try to think of an answer, I'll tell you. They have nothing to do with each other, fatigue life is a function of loading, not deflection. Therefore, stiffness isn't as important as you think.

The reason Al frames are overbuilt is to try to increase the fatigue life by adding more material.

I had a talk to a material science professor a few months ago about this, if I can remember I'l lpost what he said.


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## Motivated (Jan 13, 2004)

*I think that is actually what DeeEight is saying*



novice said:


> DeeEight, why do you keep talking about stiffness and fatigue?
> 
> While you try to think of an answer, I'll tell you. They have nothing to do with each other, fatigue life is a function of loading, not deflection. Therefore, stiffness isn't as important as you think.
> 
> ...


Since some magnesiums approach the properties of typical aluminums, but are more fatique resistant the frames do not have to be overbuilt. That is where the weight savings comes from. Similarly, as I mention above it is easier to design and machine parts from lower density material because the thin sections which don't carry much load don't have to be made as thin as they do from more dense material.


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## DeeEight (Jan 13, 2004)

novice said:


> DeeEight, why do you keep talking about stiffness and fatigue?
> 
> While you try to think of an answer, I'll tell you. They have nothing to do with each other, fatigue life is a function of loading, not deflection. Therefore, stiffness isn't as important as you think.


Because with ALUMINIUM, which has no clearly defined fatigue limit (unlike magnesium, titanium, and steel), the fatigue life is totally dependant on deflection. The load size makes very little difference because EVERY SINGLE deflection the part made of aluminium undergoes, brings it one step closer to a fatigue failure, regardless of how much of a load is placed on it. You absolutely HAVE TO overbuild Al structures for extra stiffness if you expect them to survive a reasonable amount of time.

With Steel, Ti or Mg, which have defineable fatigue limits, you can build a part to withstand a near infinite number of cycles for a given load. You might want to go back and talk to that materials professor again and have him explain to you about the difference between aluminium and steel.


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## ThaFurnace (Jan 12, 2004)

novice said:


> DeeEight, why do you keep talking about stiffness and fatigue?
> 
> While you try to think of an answer, I'll tell you. They have nothing to do with each other, fatigue life is a function of loading, not deflection. Therefore, stiffness isn't as important as you think.
> 
> ...


Agreed.

I would like to clarify that fatigue life is a function of the magnitude of cyclical loading, and the number of cycles to be endured. The design criterion is to find out how many cycles of a respective load your part is to endure. The same part can have an infinite fatigue life at small loads and a fatigue life of 2 cycles if the load is large.

Also, bikes do not only experience one type of loading. They must endure shear loading, compressive/tensile loading, torsion loading as well as bending. The designers have to decide which criteria to use (von mises, tresca, etc) to determine the fatigue life of the design. All of this is entirely independent of the stiffness of the material. Stiffness is a desired trait in a frame so that you don't feel like you're riding on a wet noodle and must be taken into consideration when building a frame. For example, you could build a super light frame made of thin kevlar/cf composites that would have an infinite fatigue life, yet would not be rideable because your bottom bracket would be shifting side to side at every turn of the crank.


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## Motivated (Jan 13, 2004)

*please oblige*



DeeEight said:


> 1) I could post a couple dozen Mg alloys that exceed 40ksi yeild strength.
> 
> 2) Magnesium frames are specifically popular because they ride better than aluminium frames.
> 
> 3) Magnesium also dampes vibrations better than aluminium. This is a property of the material. This is why Easton makes magnesium stems.


1) Please oblige - I'd like to see just 6 magnesium alloys that have ultimate and yield strength higher than AL7005 T6. I figure I can learn something here.

2) So above you said there isn't demand for Mg frames - here you say they are specifically popular. Which is it?

3) Yeah, I said that. Now, if Mg has a defined yield, is light, dampens vibrations AND is easy to extrude, then please find a magnesium baseball/softball bat.


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## BadHabit (Jan 12, 2004)

This reply is so subjective it's almost OT. I sure enjoy the riding characteristics of my mg ht frame (Lodestar). It employs shaped (oversized, ovalized) tubes, by the way. Corrosion isn't an issue for me. Light (2.7 lbs 17"), stiff and vibration-damped. D8 knows whereof he speaks about mg. I seem to recall that mg has to be welded in a special gas environment?


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## Motivated (Jan 13, 2004)

*Oh yeah, pics*

Here are the top Merida MTB frames. One is magnesium the other is 7005 aluminum.


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## novice (Jan 14, 2004)

I think the reasons for the lack of mg parts was due to toughness, which is not a direct material property, but directly related to ductility. The less ductility a material has, the lower the toughness, and the easier for a small defect to cause a complete failure. This a simplified theory based upon the pricinples of linear elastic fracture mechanics. I believe this is also reflected in the notch sensitivity factor(q) involved in stress concentrations for fatigue, as the low toughness corresponds to a low q value. This then lowers the fatigue limit.

edit:
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MMAM50AF
after reading that, toughness must not be the reason.

edit, again:
if you want to compare apples to apples, then compare high-zoot alloys to other ones. In this case look at high strength, low density al alloys, specifically al-li (8XXX, 209X, and weldalite).
http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MA8090T511


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## DeeEight (Jan 13, 2004)

*Bzzzzt Wrong! Again, thanks for playing....*



Motivated said:


> 1) Please oblige - I'd like to see just 6 magnesium alloys that have ultimate and yield strength higher than AL7005 T6. I figure I can learn something here.
> 
> 2) So above you said there isn't demand for Mg frames - here you say they are specifically popular. Which is it?
> 
> 3) Yeah, I said that. Now, if Mg has a defined yield, is light, dampens vibrations AND is easy to extrude, then please find a magnesium baseball/softball bat.


READ WHAT I SAID. Don't make up stuff that I supposedly said to suit your lame theory. READ EXACTLY what I said.

Stupid statement/question #2..

Five hours ago...

The structural grades of magnesium alloys, both the castable ones and the weldable ones compare quite closely to 6061T6 and 7005T6 aluminium in terms of strengths, and this is quite suitable to making frames from. The reason more parts aren't made from it is a question of lack of demand.

I CLEARLY SAID MORE PARTS AREN'T MADE FROM IT IS A QUESTION OF LACK OF DEMAND.

Stupid Statement/Question #1...

One hour ago...

Secondly I could post a couple dozen Mg alloys that exceed 40ksi yeild strength. That's one of the reasons why Mg is used in fork leg castings (which includes the fork brace btw). Its replaced 6061T6 which was the previous choice alloy for most fork makers doing sliders and braces.

NOWHERE DID I SAY I WAS GOING TO POST A COUPLE DOZEN ALLOYS THAT HAVE ULTIMATE AND YEILD STRENGTHS HIGHER THAN 7005T6.

Now since you're obviously a lazy moron who can't be bothered to use the matweb material property search form, which is pretty damn simple to use when you ask for a list of Mg alloys with an Ultimate Tensile strength of at least 310MPa and an Ultimate Yeild Strength of 275MPa (which are 6061T6's numbers), but the matweb site (which isn't totally complete of all alloys out there - its missing several hundred russian alloys, probably because their designation systems are different than US designations) came up with 5 matches to the search, and four of those matches beat 7005T6's properties (which are 350MPa UTS and 290MPa YTS).

In order of the search, the five results were

1. http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MMAZ80 (380MPa UTS / 275MPa YTS)

2. http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MMEA51 (425MPa UTS / 370 MPa YTS)

3. http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MMEA53 (515MPa UTS / 460 MPa YTS)

4. http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MMZC73 (360MPa UTS / 340MPa YTS)

5. http://www.matweb.com/search/SpecificMaterial.asp?bassnum=MMZK60 (365MPa UTS / 305MPa YTS)

If you search for equal or better on one or the other properties, 15 Mg alloys came up on the search.

Stupid statement/question #3...

As to baseball bats. 3 seconds and a google search...

http://www.tgoemall.com/shop/baseball/Worth_Youth_Aluminum_Bats.html

scroll halfway down, copperhead MG46 alloy baseball bats.

I'm now awaiting your next stupid question/statement?


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## Ultra Magnus (Jan 13, 2004)

I found five, I hope that sufices.. 7005-T6 has a yeild tensile strength of 42,100 psi, here are 5 (or 4, Items 3 and 4 are basically the same alloy, just made by different process) mag alloys and their yeild tensile strengths. There are many more that are barely weaker, like in the 38,000 psi tensile strengths, that could maybe make the 12, although they aren't technically stronger.

1 Magnesium EA55RS-T4, Extruded 53700 
2 Magnesium EA65RS-T4, Extruded 66700 
3 Magnesium ZC71-T6, Extruded Bars/Shapes 47000 
4 Magnesium ZC71-T6 49300 
5 Magnesium ZK60A-T5, Extruded 44200

What the hell, I thought I'd post the other alloys that are close but not quite as strong as 7005. Closer to 6061.. anyway, here they are:

1 Magnesium AZ80A-T5, Extruded 39900 
2 Magnesium AZ80A-F, Extruded 36300 
3 Magnesium AZ80A-T5, Forged 36300 
4 Magnesium AZ80A-T6, Forged 36300 
5 Magnesium HM31A-T5, Extruded Solid Shapes 39200 
6 Magnesium ZK40A-T5, Extruded 37000 
7 Magnesium ZK60A-F, Extruded Solids 37700 
8 Magnesium ZK60A-T6, Forgings 39200


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## DeeEight (Jan 13, 2004)

bmadau said:


> Check out these:
> 
> http://matweb.com/search/SpecificMaterial.asp?bassnum=MA9WELD8
> http://matweb.com/search/SpecificMaterial.asp?bassnum=MA7001T6
> ...


The first on the list is an Al-Li alloy used in military aircraft and INCREDIBLY expensive (plus you basically have to be a defence contractor to buy it as I recall, in otherwords, they'd probably sell it to Burt Rutan, but not to Gary Klein).

The second is 7001T6 which isn't readily weldable as I recall, is pretty damned expensive, and a lot of 7xxx series alloys are actually really annoying to have to machine parts out of (which is why you see a lot more machined 6xxx series parts in bicycle land).


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## Ultra Magnus (Jan 13, 2004)

Yeah, I've gotten a lot of greif for using 7075 on a lot of things. I've gotten so used to it that I've been guilty of spec'ing it by habit for parts that could be 6061. I'd say 90% of the 5th element air is made from 7075....


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## Motivated (Jan 13, 2004)

*Never seen a magnesium bat . . .*

. . . in a store, so was curious about the one you found. Seems it is "magnesium enhanced" (I assume aluminum) and is not truely a magnesium alloy - especially not for $85.

Now, I'm hoping to learn some things about magnesium here. So, on your list of 5 (actually the first has a lower yield strength than 7005 T6 which makes a list of 4) which are weldable and extrudable? Where are you looking for this info? I still maintain that magnesium is not common because it does not have any structural benefits over aluminum. Yes it does have better damping characteristics.

I see what you were saying regarding the structural magnesiums being suitable for making frames, SO the reason more parts aren not made from magnesium is due to lack of demand. Now if that is the case then why do only two major frame manufacturers use magnesium but many parts manufacturers do use it? As you indicated my Marzocchi fork has a magnesium crown, plus Easton makes stems, there are some brake calipers, etc.


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## DeeEight (Jan 13, 2004)

manufacturing costs/issues have as much to do with it as material costs. Look at seatposts. You either setup the equipment to custom draw/extrude/forge/cast EACH individual seatpost shaft size, or you machine them using a bunch of lathes but the same machine can make every size of shaft with a simple reprogramming. Depends on the production volume involved. Kalloy extrudes their chromoly seatpost shafts (in fact most CrMo post shafts are extruded the same way different diameter frame tubes are). Thomson which produces on a far smaller scale, and Syncros also as an older example, machines their post shafts. Thomson though might make 1/100th as many seatposts in a year as Kalloy does, and in Thomson's own tests a few years ago, the kalloy 4130 CrMo post was the fourth strongest on the market at the time. This is also why many brands only offer certain sizes of high-end machined parts. Its just not cost effective to have a wide range of sizes. Easton only offers three or four casting sizes for their Magnesium stems as I recall. Thomson only offers like 7 total seatpost diameters as I recall (26.8, 27.0, 27.2, 28.6, 30.9, 31.6, and 31.8 - those being the 7 most popular sizes for the market they're trying to sell to).


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## DeeEight (Jan 13, 2004)

Motivated said:


> . . . in a store, so was curious about the one you found. Seems it is "magnesium enhanced" (I assume aluminum) and is not truely a magnesium alloy - especially not for $85.
> 
> Now, I'm hoping to learn some things about magnesium here. So, on your list of 5 (actually the first has a lower yield strength than 7005 T6 which makes a list of 4) which are weldable and extrudable? Where are you looking for this info? I still maintain that magnesium is not common because it does not have any structural benefits over aluminum. Yes it does have better damping characteristics.
> 
> I see what you were saying regarding the structural magnesiums being suitable for making frames, SO the reason more parts aren not made from magnesium is due to lack of demand. Now if that is the case then why do only two major frame manufacturers use magnesium but many parts manufacturers do use it? As you indicated my Marzocchi fork has a magnesium crown, plus Easton makes stems, there are some brake calipers, etc.


Sigh, do I have to keep going over this...pretty much any structural grade alloy that can be cast can also be extruded, or forged. Its just a question of the manufacturers equipment. And even if it can't be welded, you can bond a frame together from it just fine. Or cast as 1-piece (as Kirk precision used to do). Trek used to make 7075T6 aluminium frames for about 8 years, that were bonded together. What a manufacturer chooses to use has more to do with whatever production facilities they have, and what end result they're trying to achieve, than what alloy (of any material) is better than any other alloy. 6061T6 is basically the WEAKEST structural aluminium alloy used in bicycle parts/frames, and even though there are far better alloys, cannondale has never chosen to use anything but 6061 for their frames.

The Mg46 alloy used in the bats IS a magnesium (primary element) alloy. WorthSports is the originator of aluminium baseball bats and still basically one of the leaders in the industry. They make the Mg bats. They also used to make titanium bats too (and those got banned by the major softball associations).


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## Jm. (Jan 12, 2004)

if it was simply just a case of demand the aircraft industry then Mg would obviously be the metal of choice.

It is not, most of it has to do with the corrosion properties, and yes it is used in aviation, but it's to a very limited extent, there is simply no demand to make an aircraft out of magnesium. I


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## ThaFurnace (Jan 12, 2004)

Jm. said:


> if it was simply just a case of demand the aircraft industry then Mg would obviously be the metal of choice.
> 
> It is not, most of it has to do with the corrosion properties, and yes it is used in aviation, but it's to a very limited extent, there is simply no demand to make an aircraft out of magnesium. I


Mg is used in aviation for wheels, casings, etc. No structural parts of airplanes are made of magnesium. This is probably due to a couple of things: namely the fact that magnesium is usually cast, and that magnesium has a tendency to creep. Structurally, the yield strength of magnesium is about half that of an aluminum alloy, and a quarter of carbon fiber's. For a structural application, CF+AL are superior to Mg. That's why you don't see Mg airplane wings.


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## DeeEight (Jan 13, 2004)

ThaFurnace said:


> Mg is used in aviation for wheels, casings, etc. No structural parts of airplanes are made of magnesium. This is probably due to a couple of things: namely the fact that magnesium is usually cast, and that magnesium has a tendency to creep. Structurally, the yield strength of magnesium is about half that of an aluminum alloy, and a quarter of carbon fiber's. For a structural application, CF+AL are superior to Mg. That's why you don't see Mg airplane wings.


depends on the alloy, a couple of the Mg alloys we provided links for above are superior to 6013 in strength, and that's an Al alloy that is extensively used in fuselages and wings. The reason for no Mg wings is again, corrosion, and expense, not to mention, melting points and thermal conductivity.


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## PSTOST (Feb 27, 2004)

There is no big problems with mag in bicycle parts - but as d8 says it has corrosion problems and is not widely used in any industry. To use mag you have to do some more R&D compared to just use the "normal" alloys such as 6061, 7005 and 7075 - and without any real benefit .
But mag parts in the car industry is getting alot bigger these years - so I think this will help on the pricing and "not-commonly-used" issue...
I find strange that 6061 and 7075 alloy is used so much in bikeparts (I think 7075 is min 20years old) 
Much better alloys is in the market with 15-20% more strenght. It looks like most just use 7075 because everybody else is using it - instead of trying to go with something better for an small extra charge for the final product. (the bat industri use more super alloys than the high end bike industri ?)

Sugino made a crankset where alot was done to min. the corrosion. A speciel bottomb. was made with an oversize aksel and special alloy insert in the arms etc.
Weight was 845gr - so not really light.
Vuelta is also doing a 6 spoke wheel(not light !) - Many pedals are partly made of mag - Pinarello is doing frames as well - American Classic is doing a rim (I see big potencial here !)
Lets hope for more mag parts/bikes in the future


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## Ultra Magnus (Jan 13, 2004)

I ran across a link a couple of weeks ago, researching mag, and it seems that I found a site where they explained a lot about the "secrets of magnesium" because as you all are finding out, there isn't a lot of public information about mag. What I remember is that magnesium isn't manufactured in NEARLY the qty's of alumin (world production in tons produced annually) and that magnesium is produced from primarily sea water. I guess the salts in the ocean contain magnesium, at the very least, they stated the becaus of the oxidation of magnesium, there isn't any chunks of magnesium in the ground that can be mined like copper, steel, al, etc... It all has to be collected through some complex process of electrolysis or some thing I didn't fully understand. I was very intrigued though. I'll look up the link and see if I can find it. Oh, also they said that the majority of the worlds production of magnesium was sold as an alloying ingredient, not as a raw material for manufacturing.


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## Ultra Magnus (Jan 13, 2004)

Here's a link to some information on magnesium...

http://www.members.tripod.com/Mg/mggen.htm


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## rapwithtom (Feb 26, 2004)

*Now just tell me...*

Guys -

I am happy to see a bunch of materials science geeks have a huge pissing contest. It was interesting reading, thanks I learned a lot.

However, I am still confused as to whether the Easton Mg Stem I have on my XC racer is a good thing or not (I am 200lbs, so value strength, but I am still a weight weenie!).

Let me know!

Tom


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## DeeEight (Jan 13, 2004)

*The Easton Mg stem is plenty strong enough...*

for 200 pound riders doing XC. Its not actually that light a stem compared to some of the wonderlight Al and Ti XC stems. The Easton stem isn't designed as an XC stem mind you, its designed as a DH stem, and compared to most DH stems, it is damn light.


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## Jm. (Jan 12, 2004)

DeeEight said:


> for 200 pound riders doing XC. Its not actually that light a stem compared to some of the wonderlight Al and Ti XC stems. The Easton stem isn't designed as an XC stem mind you, its designed as a DH stem, and compared to most DH stems, it is damn light.


it had a severe problem with corrosion.


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## Duckman (Jan 12, 2004)

I have one. Stiff is right. Around 180gms maybe? No corrosion probs yet. Ugly tho, as its that natural color deal.


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## eric (Jan 22, 2004)

Okay, my apologies here. I didn't realize Merida actually does use magnesium tubing.


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## Max (Jan 13, 2004)

eric said:


> Okay, my apologies here. I didn't realize Merida actually does use magnesium tubing.


actually their LRS XC-duallies come with an ordinary alloy tubing this year. the old ones made from some Mg-alloy were too expensive and broke all the time. just like the hardtails..... i got 5 fellow riders on meridas (racers, just like me) and 4 frames were broken during one season...... i'm no longer a team merida austria rider but i used to and so i know about many cases with broken seat-stays etc.


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