639283.fig.001a
(a)
639283.fig.001b
(b)
639283.fig.001c
(c)
639283.fig.001d
(d)
Figure 1: Microstructure of heat-treated (a) reference steel at 1100°C, (b) reference steel at 1200°C, (c) modified steel at 1100°C, and (d) modified steel at 1200°C (etched with 40% glycerin, 40% nitric acid, and 20% hyrochloric acid).