The fracture toughness values for Ni-W alloy were calculated, assuming a linear elastic behaviour, from the fracture loads of the cantilever beams using the following equations: K_k=(6PL)/(bh~2)·(πa)~(1/2).F(a/h) F(a/h) =1.12-1.39(a/h) +7.32(a/h)~2-13.1(a/h)~3+14.0(a/h)~4 where, P is the load at fracture, L is the distance between the notch and the point of application of load, b is the beam width, h is the beam height, a is the depth of the notch, and F(a/h) is given in [24]. The length, I, was determined from an image saved whilst positioning the tip in the nanoindenter. The width, b, was measured from the SEM image taken before testing. Notch depth, a, was measured from SEM images taken after testing. The distribution of fracture toughness values thus obtained is shown in Table 3 and lies within the range of 1.49-5.14 Mpam~(1/2).
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