1. Chemical Services Routine Request JUL13187
Horizon Aluminum Conductor
Thread Cross Section
Composition, Hardness, Silver Plating Thickness July 24, 2013
Page 1 of 6
BACKGROUND
S. Nelson submitted a sample of the Horizon Aluminum Conductor to Analytical Services for
analysis. Reportedly, the device had been electrically tested. The threads cross section is
illustrated in Photo #1. The aluminum conductor has been silver plated.
Photos have been removed for size consolidation.
Photo #1 10X
The request was made to check the material hardness on the threads and plating thickness. The
material composition was also checked to determine the composition of the aluminum substrate.
Note the missing or damaged threads from the electrical test.
TEST PROCEDURES AND EQUIPTMENT
 Chemical Composition
The chemical composition was obtained with the Bruker SRS 3000 X-ray Florescence (XRF)
instrument. M. Dwyer completed the analytical work under Chemical Services Routine Request
Number JUL13187. The results are reported in the body of this report
 Hardness, Microhardness and Microstructures
A transverse cross section of the thread was mounted in Buehler Epomet ® epoxy compound.
Microhardness testing was done on the threads. The section was polished with silicon carbide
media ranging from 120 to 600-grit and a Buehler ®-polishing wheel until planar. The final
finish polish was obtained using Buehler Metadi ® Diamond compounds ranging from 9 to 1
micron in particle size. The sample was prepared in accordance with good metallographic
practice and ASTM E3, or the “Standard Practice for Preparation of Metallographic Samples”.
The microhardness values were obtained near the apex, the pitch diameter and at the root of the
threads with the Wilson MO microhardness tester. The Knoop hardness values were converted
Rockwell Hardness “B” or HRB.
The microhardness was also obtained from the microstructure away from the threads in order to
determine the effect of heat.
Images of the microstructures were obtained at 100-times magnification to illustrate the effects
of heat.
 Plating Thickness
After the sample was mounted, the plating thickness measurements were obtained with the
Nikon Stereo Zoom Microscope at 400 times magnification.
RESULTS AND DISCUSSION
1. Chemical Composition

2. Chemical Services Routine Request JUL13187
Horizon Aluminum Conductor
Thread Cross Section
Composition, Hardness, Silver Plating Thickness July 24, 2013
Page 2 of 6
Table I reports the chemical composition of the sample. The sample was compared to a 6061
aluminum alloy per ASTM B-211 or the “Standard Specification for Aluminum and Aluminum-
Alloy, Bar, Rod, and Wire”.
Table I
Element and Chemical
Symbol
Aluminum Alloy 6061 per
ASTM B-211
Horizon Aluminum
Conductor
Lab Reference No. JUL13187
Minimum Maximum
Aluminum, Al Remainder Remainder
Silicon, Si .40 .8 .8
Iron, Fe .7 .32
Copper, Cu .15 .40 .28
Manganese, Mn .15 .098
Magnesium, Mg .8 1.2 1.1
Chromium, Cr .04 .35 .098
Zinc, Zn .25 .13
Titanium, Ti .15 .03
The sample satisfies the chemical composition for Aluminum Ally 6061 per ASTM B-211.
2. Hardness, Microhardness and Microstructures
The microhardness was obtained at five (5) sites. Three (3) measurements were taken along the
thread. A fourth measurement (1) was taken in the middle of the thread. The fifth measurement
(1) was taken at the root of the thread. The measurements were taken in micrometers, converted
to Knoop hardness (KHN) values and then converted into Rockwell Hardness “B” or HRB
values. The HRB values ranged from 57.5 to 63 HRB. The average Microhardness value was
measured to be 60.3 HRB.
Photo # 2 illustrates the microstructure near the thread were microhardness values were obtained.

3. Chemical Services Routine Request JUL13187
Horizon Aluminum Conductor
Thread Cross Section
Composition, Hardness, Silver Plating Thickness July 24, 2013
Page 3 of 6
Photo # 2 100X
Photo # 2 illustrates the microstructure of the material near the threads. Note the large clusters of
intermetallic compounds that were observed. These large intermetallic clusters are probably the
result of heat around and thru the threads. Photo # 3 further illustrates the nominal
microstructure from an area that does not appear to have been heated.

4. Chemical Services Routine Request JUL13187
Horizon Aluminum Conductor
Thread Cross Section
Composition, Hardness, Silver Plating Thickness July 24, 2013
Page 4 of 6
Photo # 3 100X
Photo # 3 illustrates the microstructure of the aluminum from an area that does not appear to
have been heated. Note that the intermetallic clusters are much smaller.
The conventional material hardness was collected from the end of the conductor away from the
threaded opening and further away from the heat. The HRB values ranged from 57 to 58.3 HRB.
The average material hardness value was measured to be 57.6 HRB.
The material hardness appears to be slightly higher around the thread area.
3. Plating Thickness
Photo #4 illustrates the silver plating thickness of the sample.
Photos have been removed for size consolidation.
Photo # 4 400X
The plating thickness was taken at the top of the thread. The silver plating thickness of the
sample ranges from .00041 inches to .00074 inches. The average measured plating thickness
was .00056 inches.
CONCLUSIONS
Based on the results discussed in this report, the following conclusions are suggested.
1. S. Nelson submitted a sample of the Horizon Aluminum Conductor for analysis of the
threaded opening. The device had been electrically tested and missing or damaged
threads were observed.

5. Chemical Services Routine Request JUL13187
Horizon Aluminum Conductor
Thread Cross Section
Composition, Hardness, Silver Plating Thickness July 24, 2013
Page 5 of 6
2. The chemical composition of the Conductor satisfies the 6061 Aluminum as per ASTM
B-211.
3. The microhardness measured on the threads averaged to 60.3 HRB near the heated
threads. Large clusters of intermetallic compounds were observed near the heated area.
4. The conventional hardness of the Conductor averaged about 57.6 HRB. The heat near
the thread appears to have increased the material hardness slightly.
5. The average silver plating thickness on the threads was .00056 inches. This appears to be
a reasonable thickness considering that this is the plating thickness inside of a cavity.
6. The localized thread damage suggests that the current transfer is not uniform. The
interface between the stud and thread may be problematic for electrical transfer.
Metallurgical notations and observations were conducted under the guidance of Assistant
Laboratory Manager B. Kirk.

6. Chemical Services Routine Request JUL13187
Horizon Aluminum Conductor
Thread Cross Section
Composition, Hardness, Silver Plating Thickness July 24, 2013
Page 6 of 6
KEY WORDS
Horizon, Aluminum, 6061, Composition, Microhardness, Plating Thickness, ASTM B-211,
Conductor, missing, damaged, threads