**2.2 Preparation of metal specimen**

The iron specimens have a composition (wt%) of 0.200% C, 0.500% Si, 1.600% Mn, 0.035% S, 0.035% P, 0.040% Nb, 0.012% N, 0.020% Al, and remaining Fe. This sample was analyzed in the Atomic Energy Commission and abraded with a series of emery papers 400, 1200, 1500, and 1800 grades. The samples were then washed thoroughly with distilled water and dried in air.
