This is something I have wondered for a long time. Why are some materials like steel, diamond, and even light materials like graphene stronger than others? Is it due to the strength of the electromagnetic/static fields that repel two binding atoms? Or is it something else?
[Physics] What makes materials hard and strong
atomselectromagnetismelectronsmaterial-science
Best Answer
For crystal materials like diamond, this is a result of extremely stable bonds between the constituent atoms of the material. These bonds are only formed under immense pressure because inter-atomic repulsive forces keep the atoms from coming close enough to be forced to arrange themselves in that crystal structure.
Metals alloys like steel are much harder than elemental metals because they are a mixture of different elements like iron, nickel, chrome, etc. Basically, when a metal is composed uniformly of the same atom, they fit together very tightly and slide over each other easily. This is why pure gold is so soft and malleable.
A steel alloy, on the other hand, is composed of a few different elements. The different sized atoms mixed around in the bond structure cause irregularities in the atomic organization of the material, which makes it makes harder for slips and other deformations to occur.