Two things to check: Inspect brake pads and make sure that the pad lining hasn't worn done to the extent of metal to metal noise, however, this noise would most likely occur with braking, not turns. Next, there's a metal plate behind the rotor that can make a lot of noise if it contacts the rotor, and sometimes this noise is related to turns. If this is the case, just take a large screwdriver and bend the plate back a little.