Yes you can do that, however some cautions apply-
You did not say, but I assume you are going to use them with step sticks or a controller board having chopper logic to regulate the phase current?
If so, you should be just fine.
However if you run them on 12 volts directly (such as driving them with switches, transistors or relays without using chopper drive logic or limiting resistors) they will overheat quickly and be destroyed.
You will not be able to get as much speed out of them using 12 volts because there will be less overhead voltage to counteract the back EMF that they generate as they are moving.
And especially if using TMC2100 driver sticks they may become noisy and/or erratic in operation because those particular chips do not play well at lower voltages (been there, done that, and also I have a neighbor who is a Trinamic rep and he has told me the same thing).
So stick with A4988 or DRV8825 step sticks or driver chips when operating at 12 volts.
Sorry for the somewhat complex explanation but without knowing exactly how you are planning to drive them the answer is slightly less certain.......