Nickel steel partially pre-alloyed, .7% C, 7.5% Ni, .4% Mo, 1.5% Cu, 7.2-7.5 g/cm3.FP= fine pearlite, D= Diffusion zone around plain iron carbon from the nickel, P= normal pearlite from plain iron, A= retained austenite, M=martensite platelet, E-E= eutectoid from pre-alloyed steel and Ni= an austenitic nickel-rich region.