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Nonferrous Metals
       Nonferrous metals are those that do not have iron as the primary
element. Aluminum alloys are the most common. Aluminum is one
third the weight of steel, yet some of the aluminum alloys exhibit
strength superior to low carbon steel. Aluminum is not nearly as
strong or wear resistant as alloy steel, but has unique vibration
damping properties that make it a desirable choice for connecting
rods in certain high end applications. Most pistons are aluminum,
too.                                                                                              

 Like steel, common wrought aluminum alloys use a four digit
designator. The 1xxx series basically is 99 percent pure aluminum
without any major alloying elements. The 2xxx through 9xxx series
are structural alloys. The first digit indicates the major alloying
element. The second digit indicates alloy modification. If the second
digit is 0, it indicates the original alloy; digits 1-9, assigned
consecutively, indicate alloy modifications and the last two digits
serve only to identify different alloys in the group. The type of heat
treating process is indicated by a "-T" followed by one or more digits
that indicate the method used to produce stable tempers. Aluminum
alloy series and their major alloying elements used in engines
include:                                                                                            
Copper; when properly solution heat treated and
artificially aged, its mechanical properties are equal
to low carbon steel. Used in high end pistons today
and to make aluminum rods back in the 1960s.
2xxx
Silicon; when properly heat treated these high temp
aluminums make good, durable piston material with
a low coefficient of expansion.
4xxx
Magnesium and silicon; less strong than 2xxx and
7xxx aluminum; has good formability and is OK for
semistructural use, but not for critical parts.
6xxx
Zinc; when combined with a smaller percentage of
magnesium, results in higher strength alloys than
even the 2xxx series. Trace copper and chromium
must be added to improve ductility. Requires both
solution heat treatment and artificial aging. Modern
aluminum rods basically use modified 7xxx alloys.
7xxx
Cast aluminum alloys have a different three digit
designator system. 356 through 390 are used to
make cast pistons. Properties are close to 6061.
3xx
          Many of the standard alloys (steel as well as aluminum) were
originally developed for airframe use, then adopted for automotive
engines. In aircraft structure, low temperature, corrosion resistance
and extremely long fatigue life are priorities, where in an automotive
engine, higher temperatures and tensile strength are more important.
For these reasons, many of the leading manufactures have evolved
proprietary (and closely held) variations of the standard alloys that
may not have a specific standard numerical designator.                

       Really exotic applications have experimented with titanium
alloys. Titanium rods have been used in F1 cars. Some titanium
alloys posses the highest strength to weight ratios of all structural
metals. Titanium's fatigue properties are higher than any other
nonferrous metal, as long as there aren't any surface imperfections.
But titanium is extremely notch sensitive; any scratch or nick creates
a stress riser that can cause a crack to from. Titanium surfaces gall
easily' so they need some kind of surface treatment to run against
other parts. And titanium cost really big bucks.                                   

       The latest developments are composite materials that contain
aluminum with some nonmetallic fiber or compound, such as
ceramics (clay). Such designer materials have greater potential but
are just now finding their way into the civilian market. Ultralloy
actually is a high tech composite aluminum ceramic material that is
ultralight and ultrastrong, yet unlike similar aluminum matrix
composites can be machined without costly diamond tooling.