Standard Romex is a three-strand, solid core wire, individually insulated, in a common sheath to make it easier to pull. For a short time, some manufacturers were making romex with aluminum because the cost of copper was so high, but the aluminum wire was not as good as the copper, and the practice was discontinued.
No, do not mix aluminum wire with copper wire.
Copper is preferable to aluminum and the size of wire should be the same or the next size down if copper is used.
In the electrical trade aluminum wire is equivalent to copper wire as it is also used to carry current. To carry the same current as copper wire aluminum wire is up sized to meet the same ampacity.
Aluminum and Copper Wire
Copper or aluminium.
Aluminium wire has high resistance than Copper.
Romex is a manufacturer's wire cable trade name, the 10 refers to the size of the wire inside the cable set. A #10 AWG copper conductor with an insulation factor of 90 degrees C is rated for 30 amps.
When compared by volume, copper is best, then aluminum and finally iron. When compared by weight, aluminum is better than copper. You have to compare by volume because aluminum is so much lighter than copper, an aluminum wire that weighed the same as a copper wire would be much bigger and harder to work with.
#1 copper thhn
copper, aluminum, and steel
A #10 copper wire in a NMD90 cable is rated at 30 amps.
copper plated aluminum wire