Molybdenum/Tungsten alloy armor piercing round As we all know, the military's use of depleted uranium in armor piercing rounds and shells is very dangerous as far as health concerns, and an alternative is needed. Tungsten is already a very dense metal, but molybdenum is widely used to harden metals, and also has a very high density. Would a molybdenum and tungsten alloy work for armor piercing capabilities? If so, why not?
Probably not. Molybdenum and Tungsten are both hardening alloys to steel, they perform the same function, though differently. I suspect a Mo - W alloy would have the fragility of both molybdenum and tungsten while not hardening each other especially much nor increasing density.

The answer is: Sure, it would be hard, heavy and likely armor piercing, but very inefficient use of both Mo and W. Just use W alone, or alloy it with elements that are lighter, but melt within reasonable ranges. A quick glance at wikipedia confirms that Fe, Ni and Co are usual alloying elements. Tungsten carbide is also used.

Creating this Mo-W alloy would also be very difficult, usually you solvate the high mp material in the liquid low mp material but these both do not melt within reasonable limits so you would have to use some seriously high temperature equipment, we are talking beyond bright white heat - or rely on very, very slow processes (diffusion - and these are large atoms...).