it depends on if you have 14 or 12 awg wire if its 12 just puling in  a 20 amp will fix it, it could be a bad beaker to as a beaker gets old it starts tripping at a lower amp draw, when hes going to do when he comes out is put an amp probe in your panel and see how amps your pulling on that circuit. as for all the hatting on aluminum wire its fine it wont start a fire any more then  cooper if its in good shape, the only thing that it does is you have to ues a larger gauge then you would whit copper to get the same amps