Fig. 2

SEM photomicrograph of A1 group showing (57x) multiple crack origins (blue circles, A), (100x) crack propagation direction (red dotted line, B),(250X) mirror-like zone (blue arrow), mist zone (yellow rectangle), velocity hackles (red arrows), twist hackle (yellow arrow), wake hackle (orange arrow), arrest line (black arrow) and (500x) crack lines (white arrows).