I always found it funny how people say that AL is crap for house wire, or it's never used anymore. Although it is not the prefered method of wiring a house and often frowned upon, it would work fine, imo, if sized properly. Same as with feeders; which, incidently, are mostly AL. Why? Cheaper and easier to work with. But, it was sized accordingly.
I'm sure there are a million other reasons not to use it in a house, this was just an opinion.
I welcome corrections and education on the subject.
The wire size has really very little to do with the failures of aluminum.
While this also goes for copper, almost all wire failures are at the termination point, two of the biggest differences between aluminum and copper is the type of corrosion, when copper corrodes it forms copper sulfide which is conductive, when aluminum corrodes it forms aluminum oxides which is not very conductive, thus as it looses connection from aluminum oxide it starts to heat, till it just melts down, Aluminum oxidizes very easily with just a slightly moist environment, this is where sealing the connection is very effective if the compound doesn't dry out over time, I find a good dielectric grease to be more effective then no-lox because of this.
The other problem with termination is aluminum can cold flow when terminated in a dissimilar metal terminal without any spring to allow expansion, because of the different expansion rates the aluminum will expand faster then the other metal and if there is no spring to give and to maintain a constant pressure like a expansion joint, the aluminum will cold flow out from under the terminal so when it cools you no longer have a tight connection, many terminals had a spring clip/plates that was tightened down on the conductor, but today very few terminals are made like this, never understood why? as this problem happens with larger terminals and conductors also, so I try to only use aluminum conductors where the terminals are also aluminum or have the spring tension clips/plates, and use dielectric grease.
The problem with branch circuit wiring is, to do the job properly will make the cost and labor of it not worth what you would save using it.
And the fact it would be hard to find in small AWG's as well as that many insurance companys refuse to insure a house with small branch circuits wired with it.