For instance, a typical Nichrome alloy has a resistance of $1.0 \times 10^{-6} \Omega \cdot m$, which is much higher than that of pure Nickel ($7 \times 10^{-8} \Omega \cdot m$) or Chrome ($1 \times 10^{-7} \Omega \cdot m$).
[Physics] Why do some alloys have much higher electrical resistance than their constituent elements
electrical-resistancemetals
Best Answer
A perfect crystal lattice of ions at very low temperatures would offer very little impediment to the free electrons i.e. it would have a very low resistance.
Add some imperfections like making the lattice ions vibrate as a result of them being at a higher temperature will result in more interaction between the free electrons and the ions - the resistance goes up. Dislocations in the crystal and impurities also increase the resistance. So in an alloy you have two species of ions and hence a situation which is far from a perfect crystal lattice. So there are lots of interactions between the lattice ions and the free electrons leading to a high resistance.
A free electron only "sees" imperfections and it is the interaction between the free electrons and the imperfection which is the origin of resistance. Free electrons are scattered off imperfections and alloys have many more of them than pure metals.