Question: What is the hardest material to make stronger?

Alex Leide answered on 12 Nov 2020:

hard question to answer! There are different types of “strong”: hardness, toughness, stiffness, impact… it’s complicated. Generally, you can’t change stiffness much. If you make a material harder, generally it becomes less tough, so cracks more easily.
Probably something like diamond would be impossible to make stronger? It is very hard and stiff, and any modifications you make would make it worse. You might be able to make it tougher with some fibre reinforcement.
Metals are very easy to modify. you just add some other elements, do some heat treatments, and you can tune the properties a lot depending on what you want to use it for.