For starting out I would strongly suggest 6061 or 6075. The 6xxx series is specifically designed to provide excellent milling characteristics while providing an excellent strength/weight trade off.
Stay away from 7xxx - they are near steel in hardness - and the 2xxx series too - they are high strength alloys.
Online Metals is a good US source. YMMV.
Do consider getting ZrN or TiB2 coated end mills. This will decrease the cutting resistance and allow for less heat, less end mill wear and faster feeds and speeds.
The Onsrud 63-604 is an awesome choice for milling Al alloy.
Please see:
My short term plan is to build my own vice as a learning exercise.
Truly a worth project. It’s FAR from non-trivial to make a good vise (which is why we usually buy them) but it’s also far from rocket science too!
Do consider a program like G-Wizard to deal with the feeds and speeds and cut depth.
mark
P.S.
6061 and 6075 on the Nomad as relatively easy. They can be machined dry - slowly - or with a bit of hand spray on (soy based) lubricant. It’s all about using the right depth and feeds and speeds. Comes out just fine; no need to hesitate.
I’m milling 2" x 2" x 2" blocks and 0.125" sheets of 6061-T651 right now… dust head for my Nomad 883 Pro.
When I’m done, I will do a Turner’s cube, just for grins.
P.P.S.
Mill rigidity is about accuracy and precision AND being able to maintain those at maximum rate when cutting the expected materials. The Nomad 883 was designed for Al (6061). The Nomad 883 Pro is arguably a bit better at it but not hugely so.
The Nomads are very rigid; non-ferrous metals are fine. @ApolloCrowe did Titanium (which is much harder than 6061)! Run the Nomad properly with shallow depth and the rigidity isn’t an issue.
All that said, slowing a feed isn’t the correct solution. One has to machine for RPM, feed, speed and depth simultaneously. Then Al alloy isn’t hard.