http://www.precisionsheetmetal.com/home/materials.htm

Alum has a grain, if you bend with it it will crack, always bend across the grain, rule of thumb is the bend radi is 2 times the material thickness (1/8 = .125 x 2 = 1/4"r) up to 3/32", then it's 4x,,you can go tighter on the R depending on what the Alum is, a simple brake can be made using a 2 or more ton Hyd jack and some ingenuity.