4.4. Mechanism of part burr formation—magnesium alloy
Despite the unique zig-zag fracture during trimming of the magnesium alloy samples, the burr formation mechanism appeared to be very similar to that of the aluminum alloy. Rapid crack propagation occurred after crack initiation (Fig. 13), and the lower part of the fracture surface profile was curved, with the burr closely following the shape of the die. The burr height of the magnesium alloy was lower than the aluminum alloy at most clearances, which can be attributed to the lower penetration on both the punch and die-side when crack initiation occurred (as shown by the lower rollover at all clearances for the magnesium alloy compared with the aluminum alloy).