Assuming you were asking about cutting 3/4" X 3/4" X 1/8" standard hardware store angle.
Have you considered a fine tooth hacksaw? They work great. Clean up with a file loaded with chalk or soapstone after. If not, then...
Use the highest tooth count you can find. 10 teeth per diameter inch. Tooth count and configuration depends on the alloy and thickness. The thicker the aluminum material is, the fewer teeth you typically need. (TCG) Triple chip grind tooth profile with a negative tooth angle is best. Like -5 degrees. You can use a wax to lub the blade to prevent welding of the material to the teeth of the blade. The aluminum will melt instead of cut if you go to fast and will make for a very ugly cut. Make sure you have your entire body covered in clothing, gloves, face shield, hearing protection. Use a very firm grip or clamp. One side of the angle against the fence and the other side against the table. Maybe put up some cardboard to contain the metal shavings from getting everywhere. Cover any glass in the line of fire.
This high quality blade has everything you need for your project, meets the requirement of your saw, and is readily available. I was unable to find an economical alternative with adequate specs.
You will not want to use this blade later for cutting crown molding or any lumber or boards down the road. Sorry you can not upgrade your current saw blade with this aluminum project of yours. There are wood/metal combo blades, but those are for ferrous metal. A blade made for composite decking like Trex could work if you were planning that type of work ahead. Aluminum is a specialty product and should be treated as such. I know a blade like this is expensive for small projects. I own many dozens of different types of saw blades, maybe even a hundred types. They are not a one fits all kind of thing. Sometimes you just use them once. Please do not buy a 10" saw blade for your 12" saw and attempt to cut aluminum with it. It won't cut all the way through anyway. You would need to build up your fence first. Please do not turn your saw blade backwards and cut with it. Leave that to the siding crew. It would not apply here. Buy the right tools, buy the right accessories, do it safe. If you would like to save yourself some money, get a smaller size saw for special projects and the blades will be much cheaper. Like this
I have been trained, educated, you can trust what I say to be true. I do not deny that there are other real alternatives and suggestions you will hear that will actually work, but those typically originate from having a lack of something else. Some of those can cause damage to material, damage to equipment, or even loss of bodily function. I am just trying to give the best advice I can.