Best Aluminum Grades for RC

[RonShaw]

Hey,

I wanted to get an update on the best grades of aluminum to use for different areas of our hobby. I have traditionally in the past used either 7075 or 6061 in the following areas. Any ideas or advice would be appreciated.

7075- running hardware such as brackets, mounts, rudder, struts, pipe mounts, etc

6061- head buttons, flywheels, collets, pipe stingers, headers, etc. I have also used this grade for some of the items above but usually heat-treated before use.

Thanks in advance.

 

[Hydro Junkie]

This is from the Online Metals website:

6061 Aluminum is, by most any measure, the most commonly used aluminum alloy. It is specified in most any application due to its strength, heat treatability, comparatively easy machining, and weldability. If that were not enough, it is also capable of being anodized, adding a layer of protection for finished parts.

The main alloy ingredients of 6061 aluminum are magnesium and silicon.

6061-T6 Aluminum

Physical and Mechanical Properties

Ultimate Tensile Strength, psi 45,000

Yield Strength, psi 40,000

Brinell Hardness 95

Rockwell Hardness B60

Chemistry

Aluminum (Al) 95.8 - 98.6%

Chromium (Cr) 0.04 - 0.35%

Copper (Cu) 0.15 - 0.40%

Iron (Fe) 0.70%

Magnesium (Mg) 0.8 - 1.2%

Manganese (Mn) 0.15% max

Silicon (Si) 0.4 - 0.8%

Zinc (Zn) 0.025%

7075 is the other "aircraft grade" aluminum that is carried by OnlineMetals. Its principal alloying ingredients are zinc and copper, which make it one of the highest-strength aluminum alloys that are available. In fact, its typical strength in the T6 temper is higher than most mild steels.

7075 also has average-to-good ratings for machinability, corrosion resistance, and anodizing response. Like 2024, however, it is not considered to be weldable.

7075-T6 Aluminum Physical and Mechanical Properties

Ultimate Tensile Strength, psi 83,000

Yield Strength, psi 73,000

Brinell Hardness 150

Rockwell Hardness B87

Chemistry

Aluminum (Al) 87.1 - 91.4%

Zinc (Zn) 5.1 - 6.1% max

Copper (Cu) 1.2 - 2.0%

Chromium (Cr) 0.18 - 0.28%

Iron (Fe) 0.5 max

Magnesium (Mg) 2.1 - 2.9%

Manganese (Mn)

0.3% max

Based on the above:

7075 is best for turn fins and brackets where flex needs to be avoided

6061 is best for areas that require welding or are not subject to flexing loads

2011 is the most machinable of the commonly available aluminum alloys. Machining this alloy can produce excellent surface finishes on your product, and small, broken chips.

Weldability, strength, and anodizing response are all rated as average at best, and this alloy does not have a high degree of corrosion resistance.

If the ability to make your part quickly is important to you, and strength is not the primary desire, 2011 represents a good choice if you're using aluminum.

Copper is the main alloying ingredient in 2024. It is very strong compared to most aluminum alloys, and has average machinability, but the copper component of this alloy makes it susceptible to corrosion (many items in this alloy are produced with a clad surface to protect the underlying material.) In addition, 2024 is not considered to be weldable.

Finally, the fatigue resistance of 2024 make it a primary choice when the application is expected to be under stress or strain for prolonged periods. It is commonly used in aerospace applications.

 

[JimZaremski]

2024 is also more brittle and can't be drawn/formed as easily.

 

[RonShaw]

This is from the Online Metals website:

6061 Aluminum is, by most any measure, the most commonly used aluminum alloy. It is specified in most any application due to its strength, heat treatability, comparatively easy machining, and weldability. If that were not enough, it is also capable of being anodized, adding a layer of protection for finished parts.

The main alloy ingredients of 6061 aluminum are magnesium and silicon.

6061-T6 Aluminum

Physical and Mechanical Properties

Ultimate Tensile Strength, psi 45,000

Yield Strength, psi 40,000

Brinell Hardness 95

Rockwell Hardness B60

Chemistry

Aluminum (Al) 95.8 - 98.6%

Chromium (Cr) 0.04 - 0.35%

Copper (Cu) 0.15 - 0.40%

Iron (Fe) 0.70%

Magnesium (Mg) 0.8 - 1.2%

Manganese (Mn) 0.15% max

Silicon (Si) 0.4 - 0.8%

Zinc (Zn) 0.025%

7075 is the other "aircraft grade" aluminum that is carried by OnlineMetals. Its principal alloying ingredients are zinc and copper, which make it one of the highest-strength aluminum alloys that are available. In fact, its typical strength in the T6 temper is higher than most mild steels.

7075 also has average-to-good ratings for machinability, corrosion resistance, and anodizing response. Like 2024, however, it is not considered to be weldable.

7075-T6 Aluminum Physical and Mechanical Properties

Ultimate Tensile Strength, psi 83,000

Yield Strength, psi 73,000

Brinell Hardness 150

Rockwell Hardness B87

Chemistry

Aluminum (Al) 87.1 - 91.4%

Zinc (Zn) 5.1 - 6.1% max

Copper (Cu) 1.2 - 2.0%

Chromium (Cr) 0.18 - 0.28%

Iron (Fe) 0.5 max

Magnesium (Mg) 2.1 - 2.9%

Manganese (Mn)

0.3% max

Based on the above:

7075 is best for turn fins and brackets where flex needs to be avoided

6061 is best for areas that require welding or are not subject to flexing loads

2011 is the most machinable of the commonly available aluminum alloys. Machining this alloy can produce excellent surface finishes on your product, and small, broken chips.

Weldability, strength, and anodizing response are all rated as average at best, and this alloy does not have a high degree of corrosion resistance.

If the ability to make your part quickly is important to you, and strength is not the primary desire, 2011 represents a good choice if you're using aluminum.

Copper is the main alloying ingredient in 2024. It is very strong compared to most aluminum alloys, and has average machinability, but the copper component of this alloy makes it susceptible to corrosion (many items in this alloy are produced with a clad surface to protect the underlying material.) In addition, 2024 is not considered to be weldable.

Finally, the fatigue resistance of 2024 make it a primary choice when the application is expected to be under stress or strain for prolonged periods. It is commonly used in aerospace applications.

Thanks Mark. Looks like there are a couple more choices that I need to consider. I really appreciate the feedback.

 

[RonShaw]

2024 is also more brittle and can't be drawn/formed as easily.

Thanks Jim. I'm sure others will chime in as well.

 

[Bob Kensill]

This my secret so don't tell anyone. I use 3003 H12 for my tuned pipes. It needs to be annealed before stamping. I use a kiln to bring it up to 775 degrees then cool it naturally

 

[RonShaw]

This my secret so don't tell anyone. I use 3003 H12 for my tuned pipes. It needs to be annealed before stamping. I use a kiln to bring it up to 775 degrees then cool it naturally

Thats cool Bob. I think thats how Equi used to do it as well. Thanks for sharing.

 

[Chris Wood]

yep 7075 for hardware.. also ( hydro guys ) on the turn fins.. 6061 has its place in certain areas.. struts.. drive dogs. but not on a rudder.

 

[Brad Christy]

Ron,

At least for hydros, if you make a rudder out of 6061, you will get one run out of it and it will be bent. 7075 will hold up to just about anything we throw at it. 2024 is actually better than 7075 for turn fins as it will withstand the bending and curling we put them through while making them.

2011 is the material of choice for head buttons, as I understand. It is considerably stronger than 6061 (though, not as strong as 7075), so the threads are solid. I don't understand all I've heard about it, but something about the chemical make-up makes 2011 a better choice than 2024 (detonation and such). I don't make head buttons, so I'm not the authority on the matter. I am fairly certain, though, that most OEM head buttons are made from 6061.

I make my entire rudder ass'y from 7075 because it is a very minimized, dainty looking ass'y. I use 6061 for the entire strut ass'y, and it seems to be plenty strong enough. About all the rest of my hardware is made from Delrin.

It really boils down to this: 6061 is fairly inexpensive, and therefore is the most widely used and most readily available. 2024/2011 has great thermal properties and is considerably stronger and more expensive than 6061, and 7075 is considerably stronger than 2024, but is fairly expensive, as compared to other aluminum alloys.

Titanium is the next step up from 7075, in strength-to-weight comparison, but it's a completely different animal, and several factors must be considered if you want to go that route. It is considerably more flexible than aluminum, but has great "memory", meaning it has to be severely distorted before you permanently change it's shape. Machining it is really not that big a deal, but your speeds and feeds must be right and you must keep everything cool. Slower spindle speed, higher chip load, carbide tooling and a heavy spray mist or full flood coolant is best. You don't really want to have to tap it.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine and Precision LLC

 

[El Zorro]

A lot of good information in the above posts. I have always used 2024 T3 aluminum for my turn fins. It is much stronger than 6061 but a bit more expensive. You can still put quite a bit of hook in the rigger fins without the material cracking. 7075 aluminum is harder material and more expensive than the 2024 and is much tougher to bend a hook in a rigger fin. I do use 7075 material for some of the larger rigger fin braces. Rudders are more durable when made from 7075 material or else they are prone to bending when the boat takes a hard dump ( that doesn't sound right, does it? ). As far as making head buttons or inserts I always used 2011, which contains a bit more copper in it that the other aluminums previously listed. It machines easily and I felt like it would seal better in this application because of the amount of copper in the material. It worked for me.

Dick Tyndall

 

[RonShaw]

I agree Dickie. Lots of great information, and from you as well. Thank you for sharing.

 

[BobLondress]

I am not an expert in AL alloys but in my working past we found 2024 to be the best to use in high vibration , fast cycling transfer presses. 6061 wound not last at all in these machines. I always saved scraps of the 2024 bar stock and used it for all of my hardware . I never had a failure with it in R/C boating. Now there were some failures with my driving !

 

[Glenn Gates]

The T designation following the alloy is very important. Dick uses T-3 on fins as it can be bent. T-6 is not good for bending. If the material alloy is followed by a O it means it is annealed.