Going too slow can be as bad a going too fast. When you are in the right speed zone the chips will help to carry away some of the heat with them. So getting nice sized chips helps. In wood this is the “dust” vs “chips” thing you may have seen people talk about.
Also when going too slow the bit can keep moving over the same spot on the material after it has been cut. This is called rubbing and it can build up a TONE of heat very fast. This is what causes burning or scorching when cutting wood. The cutting edges speed is a combo of both the feed and rpm. Which is why when working with wood turning down your RPM is the easiest way to adjust for any charing mid cut.
For aluminum GWizard recommends a feed rate of 35 inches per min for a 1/4" endmill when going at 18,000rpm (#3 on the dewalt) if that is too aggressive a cut try reducing the depth of cut rather than the speed. (I have been running mine at .13mm which is around .005 inches)
If you search the board for “aluminum” you can see other posts about people’s aluminum feeds and speeds and see what may work for you.
Some people are using mist coolers or just compressed air to blow aluminum chips away and cool the cut. I am planing on setting one up myself. Gantry Upgrade to C-Beam