What’s the difference that makes melted iron particles stick together into a solid shape vs simply gathering a pile of loose iron particles into a shape that can easily scatter apart?
In: Physics
Metal particles are made up of smaller crystals. When you put them in a jar, the crystals don’t bond together, the metal powder stays a powder.
Heat can soften the crystals and make them stick to each other better under pressure. This is called “sintering”, and it’s like making a snowball. The snowball isn’t a uniform solid, but the internal structures have been forced to link with each other.
Enough heat/pressure can cause the crystals to merge, a process called “forging”, where new crystal boundaries can be formed. This is like soaking your snowball in water and letting it refreeze. It’s much more solid.
Add enough heat, and you can melt the metal. The liquid can then be formed into any shape you want through casting, like wax or plaster. To overdo the analogy, this is melting the snow and freezing a new ice-sphere.
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