There was a difference in burr shape between the steel and light alloy samples. The burrs formed on the steel samples did not follow the shape of the die, instead forming a ‘v’ shape between the die tip and the bottom of the burnished section (Fig. 5a). The burr formed in both the aluminum and magnesium alloys closely followed the shape of the die, with the burr forming a right angle to the sheet/part (Fig. 5b).
There was also a difference in the profile shape of the fracture region between the steel and light alloy samples. The profiles of the steel fracture surfaces were relatively straight from the bottom of the burnished region to the bottom of the burr as shown in Fig. 5a. The fracture profile over the same region on the aluminum alloy, however, was curved (Fig. 6); convex on the part and concave on the scrap. The most notable characteristic of the magnesium alloy was the presence of a zig-zag upper fracture surface profile (Fig. 7). The lower fracture surface profile was curved, similar to the aluminum alloy (convex with respect to the part).