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Thread: Chemistry of alloy metals

  1. #1 Chemistry of alloy metals 
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    When I look up the composition of a metal like 303 stainless, I can only find the percent mixture of the various ingredients, but not an actual chemical formula of the metal, like "H2O". When creating alloys, is a new molecule even formed? or does it derive its resultant properties elsewhere?


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    Alloys are really solid solutions and chemical reactions are mostly not intended to occur to produce new molecules. However in stainless steels their corrosion resistance depends on a tightly adhering film of chromium oxide which you could say is a new molecule, and forms by reaction of the chromium with oxygen in the air. This is a desirable reaction. An undesriable reaction is the combination of some of the carbon in the alloy with some of the chromium, forming new molecules of chromium carbide at grain boundaries. This depletes the chromium from the solution and increases the alloy's susceptibility to a type of corrosion called intergranular corrosion.

    The corrosion resistant properties of stainless steels could be said to be dependent on new molecules being formed, but their mechanical properties of tensile strength and so on are dependent on the grain microstructure of the solution.


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    Alright....so you are saying that when you alloy say, aluminum with the elements necessary to make it 7075 aluminum, you aren't creating a new molecular formula, but are using those elements to solely alter the micro structure of the aluminum? So it would be like mixing hydrogen and oxygen together and still having 2 separate gasses, instead of forming water.
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

    -Einstein

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    Use your computing strength for science!
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    Forum Isotope Bunbury's Avatar
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    Yes, I think thatís right. The analogy isnít perfect because you can elevate the temperature of an alloy and still get no chemical reaction, whereas if you heat up your hydrogen/oxygen mixture it will eventually react.

    Some metals can form compounds with other metals, but thatís generally not what you get in most alloys. Also, iron does combine with carbon to form cementite in steels, which is a molecular formula that wasnít there in the raw materials. But I think your question was about whether the entire mass of the alloy is considered a ďnewĒ chemical and the answer is no.

    Iím not a metallurgist Ė but I think this is correct.
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    I find it fascinating that although a new chemical is not created...it still has unique properties as a mixture. It indicates that simple proximity between elements in an alloy generates these properties. I wonder if QM has a model for this?

    As strange as it sounds, I think you are correct though. If a new molecule were created, then how could you have alloys with 99% one material per 1% other? That would require a molecule with 99 atoms of the base element and one atom of the mixing element. 100 atoms? I've never heard of such a metallic molecule...so it makes sense that new molecules are not created.
    Of all the wonders in the universe, none is likely more fascinating and complicated than human nature.

    "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe."

    "Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence"

    -Einstein

    http://boinc.berkeley.edu/download.php

    Use your computing strength for science!
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  7. #6  
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    It is interesting. Glad you brought it up. See the link, section 4.3, for examples of metal-metal compounds.

    http://www.hull.ac.uk/chemistry/intr...anic/Chap4.htm
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