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Per Wikipedia:

An amorphous metal (also known as metallic glass or glassy metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure.

In real life, metallic glasses are usually produced as thin films or tiny droplets because their formation requires extremely rapid cooling, and only thin films or tiny droplets have a surface-area-to-volume ratio that allows heat to be removed fast enough. Metallic glasses thicker than 1 millimeter are called "bulk metallic glass" (BMG). Production of BMG typically requires the use of complicated alloys of multiple metals with different atomic radii, such that the atoms are unable to form a crystal lattice during the cooling period. Pure single-metal or simple-alloy glasses require rapid cooling "in the order of millions of degrees Celsius a second" to prevent crystallization.

The magic system I am developing would allow for essentially instantaneous cooling of a large (on the order of centimeters thick, or even meters thick, not just millimeters thick) volumes of molten metal from white-hot to ice-cold. Because of this, mages should be able to produce, for example, a bronze or iron sword or anvil made entirely of bulk metallic glass. Would this actually be useful in a pre-industrial society, as cutting implements or other tools? Basically, would the properties of bulk metallic glass bronze/iron be better or worse than regular crystalline bronze/iron?

Wikipedia claims (without citation) that "batches of amorphous steel with three times the strength of conventional steel alloys have been produced", and that "the material structure also results in low shrinkage during cooling, and resistance to plastic deformation." Citing the paper "Microhardness and abrasive wear resistance of metallic glasses and nanostructured composite materials", which "reports on as-cast bulk zirconium-based, lanthanum-based, and palladium-based metallic glasses and on melt-spun aluminum-based amorphous ribbons", it claims that "the absence of grain boundaries, the weak spots of crystalline materials, leads to better resistance to wear and corrosion."

I essentially want to know if these properties carry over to theoretical bulk glasses like an entire sword made from glassy bronze or steel. I've found sources claiming that metallic glasses are brittle, which would not be a good property in a sword, unless the force required to cause brittle fracture was greater than the forces experienced in combat. However, such sources are referring to complex-alloy glasses rather than single-metal or simple-alloy glasses.

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    $\begingroup$ Given most standard modes of plastic deformation rely on dislocation movement, which is not possible in glasses, then the result is brittle failure. But swords should be used in the linear elastic regime and not hit plastic deformation. Net difference for a weapon is, really, not that much. $\endgroup$
    – Jon Custer
    Commented Nov 9, 2021 at 23:46
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    $\begingroup$ As a side note, one of the main commercial uses of bulk metallic glasses is golf club heads - a slightly better coefficient of restitution giving the ball very slightly more range, and a clientele that doesn't care much about price... $\endgroup$
    – Jon Custer
    Commented Nov 9, 2021 at 23:48
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    $\begingroup$ I will refrain from voting on this question because I know nothing about metalworking. However, it does seem that you are asking multiple questions within the same query. The WB.SE rules limit the number of questions per query to 1. Would you mind editing your question? Perhaps it would make sense to ask one question about the usefulness of the suggested technology in a pre-industrial society (although, you will need to think of the exact criteria of usefulness) and another question about specifics related to sword forging. $\endgroup$
    – Otkin
    Commented Nov 10, 2021 at 16:09
  • $\begingroup$ FWIW, I don't know that this is answerable in any real-world kind of way -- the properties of most metals in amorphous form are more likely to be calculated than tested, as most metals are very difficult (ranging to almost impossible) to produce even in thin films in this condition (as noted in the question). This make bulk amorphous metal a form of "handwavium" that can have whatever properties your story needs, as long as it's not grossly implausible. $\endgroup$
    – Zeiss Ikon
    Commented Nov 10, 2021 at 18:27

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