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<p>[QUOTE=&quot;mithril21, post: 3459867, member: 102153&quot;]This is definitely an interesting case. </p><p><br /></p><p>It appears the fracture initiated on the obverse side and propagated towards the reverse side. This lines up with the bending. The bending stresses will put the obverse side in tension and the reverse side in compression. The compressive strength is significantly higher than the tensile strength, so you would expect the fracture to initiate on the observe side. There could be some bending fatigue. I see what might be ratchet marks and beachmarks, but it is hard to tell because the fracture surface is heavily oxidized. Fatigue is a brittle failure that can occur in ductile metals, including copper, due to cyclic stresses. I just don&#039;t know how a coin would be used in a way to subject it to such stresses. Maybe the coin was used as some type of wedge, but I would expect a lot more surface damage if that were the case. </p><p><br /></p><p>The strike at 2:00 on the reverse shows a lot of deformation and ductility without any evidence of cracking, so the material does not appear to be inherently brittle.</p><p><br /></p><p>Bismuth and lead impurities would result in precipitation of detrimental phases at the grain boundaries leading to brittle intergranular fracture. Again, it is hard to tell from the photos, but it does not seem like an intergranular fracture. You might be able to determine the fracture morphology on the SEM if it’s not completely obscured by the oxide layer.[/QUOTE]</p><p><br /></p>

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