In steel that is 0.65% carbon by weight, barely one in 34 atoms is carbon (assuming no other additives/impurities). How can such an outnumbered constituent make such a big difference? Surely many of the iron atoms are not touching any carbon.

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    $\begingroup$ Hint: crystal boundaries; edge vs. bulk properties $\endgroup$ Jun 16 '20 at 22:22
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    $\begingroup$ en.m.wikipedia.org/wiki/Steel Discusses it. A few precipitates have a large effect. $\endgroup$
    – Jon Custer
    Jun 17 '20 at 0:50
  • $\begingroup$ Think about the big strength difference 0.1 % C makes in "micro alloyed "steels. $\endgroup$ Jun 17 '20 at 16:42

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