Fatigue crack growth behavior and plane-strain fracture toughness of a multicomponent Nb–Ti–Al alloy

A study has been conducted on the cyclic fatigue crack growth and the plane-strain fracture toughness of a 44Nb–35Ti–6Al–5Cr–8V–1W–0.5Mo–0.5Hf (at.%) bcc-solid solution strengthened alloy, via compact tension testing of fatigue pre-cracked specimens at room temperature. The fatigue crack growth behavior clearly identifies a ΔKth=7 MPa√m. The da/dN−ΔK trend is essentially the same as shown for a (same category) 50Nb–37Ti–13Cr alloy and unalloyed niobium. Hence, this type of alloying has no influence on ΔKth; rather the influence is on KC. The plane-strain fracture toughness, K1C=36 MPa√m. When considered with the ΔKth=7 MPa√m, it provides a wide range to accommodate damage tolerance with respect to intrinsic or service generated defects. A comparison is made with results for various γ-TiAl alloys.