I saw a thing recently on this, but more specifically about Bronze Age axes. If you are casting and not forging, a thick area of metal would cause issues, and I wish I could remember enough details to look up why. It’s why large cast form axes have that hollow spot in the thick middle part of the axe head. Since this x is in the thickest part of the blade and that sword appears like it was cast, the purpose could be the same. It could also be just to remove weight for better balance.
My guess would be stress concentration from uneven cooling leads to embrittlement and eventual failure. You can get around it if you can do the casting in a kiln that slowly lowers the temperature, but that’s going to be hard with a Bronze Age kiln.
I saw a thing recently on this, but more specifically about Bronze Age axes. If you are casting and not forging, a thick area of metal would cause issues, and I wish I could remember enough details to look up why. It’s why large cast form axes have that hollow spot in the thick middle part of the axe head. Since this x is in the thickest part of the blade and that sword appears like it was cast, the purpose could be the same. It could also be just to remove weight for better balance.
My guess would be stress concentration from uneven cooling leads to embrittlement and eventual failure. You can get around it if you can do the casting in a kiln that slowly lowers the temperature, but that’s going to be hard with a Bronze Age kiln.