Table 1. Comparison of fracture toughness in UFG-iron and UFG-nickel. The results of Ni were re-calculated into equivalent critical stress intensities derived from crack tip opening displacement measurements [17].

Iron	KIC (MPa m1/2)	Nickel	KIC (MPa m1/2)
A	14.2	A	63.2
B	36.2	B	108.1
C	49.0	C	72.3