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Technical Discussions
Ron Olson
R & D, Aviation
The Best Aviation Company In The World, USA, Joined Feb 2005, 23

Ron Olson

R & D, Aviation
The Best Aviation Company In The World,
USA,
Joined Feb 2005
23
04:54 Oct-04-2005
Conductivity and Resistivity Values

Dear Forum,

Is (are) there an official site(s) of conducitivity and resistivity values?

I define official as being produced by the government.

I have already tried NIST (US). No go.

How about an unofficial sites? Handbook references are good (IMO better) as well.

I am particularly interested in the aluminum series. Thank you.


 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1274

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1274
06:18 Oct-04-2005
Re: Conductivity and Resistivity Values
Conductivity of a metal may be considered a characteristic property but only as a guide if you are quoting an absolute value. Usually comparisons are made to some accepted standard. Although tables such as found in the ASNT Handbook or on the web at locations such as http://www.key-to-metals.com/Article79.htm
provide values, most will caution that the values are nominal. That means for a particular alloy a range of values may be measured depending on other factors (such as heat treatment, cold working, etc.
A good reference is seen at http://www.ndt-ed.org/GeneralResources/MaterialProperties/ET/ET_matlprop_Aluminum.htm
But here is a good example of why the single absolute conductivity value is not to be used as the definitive parameter. This table shows several alloys of Aluminium.
17S Cond. "0", A51S Cond. T4 and T6, 53S Cond. "0" and 61S Cond. "0" are all aluminiums with %IACS identified as 45.00

Alloys of aluminium; 2011-T8, 3003-O, 3003-H14 and -H12, 6062-T4 and 6062-T6 (to name a few) are also found to have the same conductivity or have samples that include values in a range of conductivities that straddle 45.00.

The reference tables in the texts and on the web are handy and some extensive, but not what you might call "official"....but if it is an absolute value you are looking for a confirmation of it will not be found unless you have a sample of 100% pure annealed aluminium. Many of the Periodic Table Of Elements websites include electrical conductivity as one of the parameters of the element. But after it is alloyed and worked the electrical properties are variables

Regards
Ed


----------- Start Original Message -----------
: Dear Forum,
: Is (are) there an official site(s) of conducitivity and resistivity values?
: I define official as being produced by the government.
: I have already tried NIST (US). No go.
: How about an unofficial sites? Handbook references are good (IMO better) as well.
: I am particularly interested in the aluminum series. Thank you.
------------ End Original Message ------------




 
 Reply 
 
Chris Coughlin
Chris Coughlin
06:43 Oct-04-2005
Re: Conductivity and Resistivity Values
Ron,

NDT-ed.org has a good set: http://www.ndt-ed.org/GeneralResources/MaterialProperties/materialproperties.htm .

Hope this helps,
Chris

----------- Start Original Message -----------
: Dear Forum,
: Is (are) there an official site(s) of conducitivity and resistivity values?
: I define official as being produced by the government.
: I have already tried NIST (US). No go.
: How about an unofficial sites? Handbook references are good (IMO better) as well.
: I am particularly interested in the aluminum series. Thank you.
------------ End Original Message ------------




 
 Reply 
 
David Forsyth
R & D
TRI/Austin, USA, Joined Nov 2001, 41

David Forsyth

R & D
TRI/Austin,
USA,
Joined Nov 2001
41
09:38 Oct-04-2005
Re: Conductivity and Resistivity Values
Good points by Ed and Chris. I would use the ASM values from NDT-ed.org with confidence, but not the one from the 1955 publication. Al 2024 is not the same today as it was in 1955. ASM is probably the authoritative source for this info.

As Ed noted, product form (ie. plate, forging, rolled) and temper determine conductivity. There is a paper on ndt.net which I co-authored some years ago, showing the Al 7050 hardness-conductivity relationship with different tempers marked out.

When dealing with aerospace alloys, beware of Al-clad products. 2024T3 sheet, for example, often is sold with one or two sides "clad" with a thin layer of pure Al, which has a big influence on measured conductivity.

Dave.


 
 Reply 
 
Ron Olson
R & D, Aviation
The Best Aviation Company In The World, USA, Joined Feb 2005, 23

Ron Olson

R & D, Aviation
The Best Aviation Company In The World,
USA,
Joined Feb 2005
23
00:34 Oct-04-2005
Re: Conductivity and Resistivity Values
----------- Start Original Message -----------
: Good points by Ed and Chris. I would use the ASM values from NDT-ed.org with confidence, but not the one from the 1955 publication. Al 2024 is not the same today as it was in 1955. ASM is probably the authoritative source for this info.
: As Ed noted, product form (ie. plate, forging, rolled) and temper determine conductivity. There is a paper on ndt.net which I co-authored some years ago, showing the Al 7050 hardness-conductivity relationship with different tempers marked out.
: When dealing with aerospace alloys, beware of Al-clad products. 2024T3 sheet, for example, often is sold with one or two sides "clad" with a thin layer of pure Al, which has a big influence on measured conductivity.
: Dave.
------------ End Original Message ------------

Thank you, all.

Mr. Forsyth (or anyone else) some questions WRT the Al-Cladding.

1. How thin is the al-cladding? I believe it to be a sacrificial layer.
2. How do you remove such cladding? Mechanically? Chemically?
3. Can I include it in my calculations if I choose to keep the al-cladding?
4. How significant is al-cladding to conductivity measurements? I don't think it's that significant.

Thank you.


 
 Reply 
 
David Forsyth
R & D
TRI/Austin, USA, Joined Nov 2001, 41

David Forsyth

R & D
TRI/Austin,
USA,
Joined Nov 2001
41
02:17 Oct-04-2005
Re: Conductivity and Resistivity Values
From work published in various USAF ASIP conferences, I have some info on AL 2024T3 sheet from an older (mid 1970's) Boeing 727:

"As part of the calibration procedure for eddy current NDI, conductivity measurements were taken at several points on the top surface of the specimen. The results revealed an unusually high conductivity of approximately 50% IACS (International Annealed Copper Standard) in the lower sheet of the splice. These measurements prompted a metallurgical study of the material in both sheets to explain this discrepancy. Results are reported in section 3.1."

(from section 3.1) "The large variations in measured conductivity between the top and bottom sheets of the specimen were investigated by metallographic sectioning. It was found that the clad layer, which is a layer of pure aluminum used for corrosion protection, was much thicker on the bottom sheet. The cladding on the top layer is 50 microns, whereas on the bottom layer it is 100 microns. The conductivity of pure aluminum is muchhigher than that of Al 2024. Since the conductivity measurements are performed with an eddy current-based conductivity meter, the higher volume of the higher conductivity pure Al has a significant effect on the eddy current response."

So, to the best of my knowledge,
1. 50 microns is a good start. This info should be available from suppliers. I do not know how much this depends on sheet thickness. It is a "sacrificial" layer for corrosion protection.

2. I am not sure. Any metallurgists out there?

3. Yes, multiple-frequency ET measurements can be used with analytical models to determine thickness and conductivity of clad layer and substrate.

4. Depending on how you measure conductivity, it may be very significant.

Dave.

----------- Start Original Message -----------
: Thank you, all.
: Mr. Forsyth (or anyone else) some questions WRT the Al-Cladding.
: 1. How thin is the al-cladding? I believe it to be a sacrificial layer.
: 2. How do you remove such cladding? Mechanically? Chemically?
: 3. Can I include it in my calculations if I choose to keep the al-cladding?
: 4. How significant is al-cladding to conductivity measurements? I don't think it's that significant.
: Thank you.
------------ End Original Message ------------




 
 Reply 
 

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