# If I have an alloy of two materials, will I have a chemical reaction between the two materials

I have always been told that an alloy is a mixture without chemical interference between the materials, but if I look at highly doped silicon (doped with Aluminum via ion implantation and then lattice stabilized via annealing) then my alloy can be written as $Si_x Al_{1-x}$ which is (as I've been told) an alloy. So my question is after annealing when my Al is no longer an interstitial in the lattice but occupies a lattice site, for $x>>0; x<1$, my Al would be $sp_3$ hybridized (which in my opinion) is required for the Si to be a p-type acceptor, if my Al is getting hybridized, isn't this a change in the chemical state of the Al? Or is it only an alloy till my Al dopants behave as an interstitial but once it gets substituted into the lattice it doesn't remain an alloy, in which case graded nanocrystals of the form $Si_x Al_{1-x}$ should not be considered alloys since they are almost always annealed. Kindly help me out here.

• Yes, your first sentence is the problem - it is false. Many, nay almost all, alloys are non-ideal, having mixing terms I the free energy that depend on the various concentrations. – Jon Custer Apr 3 '16 at 16:51
• Ok, thanks a lot for your answer :). I am not a student of chemistry though, could you please point me to some literature about ideal versus non ideal alloys and their mixing terms...etc etc. – ubuntu_noob Apr 3 '16 at 16:55
• The classic book would be Porter and Easterling, Phase Transformations in Metals and Alloys. I recommend the second edition. This is more materials science than chemistry. – Jon Custer Apr 4 '16 at 0:22
• You might be interested in chemistry.stackexchange.com/questions/37635/… and physics.stackexchange.com/questions/196686/… – Jon Custer Apr 5 '16 at 20:46
• @Jon Custer: Thanks a lot, I'll post if I have further questions :) – ubuntu_noob Apr 6 '16 at 15:08