Abstract
A range of experimental titanium carbide (TiC)/nickel aluminide (Ni3Al) composites have been developed. The Ni3Al content has been varied from 15 to 40 vol.%, for two different alloy compositions. The fracture behaviour of these composites was assessed in situ, within the chamber of a field emission gun scanning electron microscope. An applied moment double cantilever beam test geometry was employed, which allowed determination of the materials fracture resistance curve (or R‐curve), while simultaneously monitoring crack–microstructure interactions. All of the tested materials exhibited a pronounced R‐curve, with fracture resistance increasing with increasing crack length, up to a steady‐state plateau value. The highest steady‐state toughness values (up to 15 MPa m−1/2) were obtained for composites prepared with the highest Ni3Al binder content. In addition, these materials exhibited the highest strength and Weibull modulus. In‐situ examination of the fracture process demonstrated considerable crack wake bridging by ductile Ni3Al ligaments, with bridging zone length of >100 μm often observed. The use of a displacement mapping technique has demonstrated that Ni3Al plastic deformation is highly localized around the crack, typically within one TiC grain width (i.e. ≈3–5 μm) away from the crack.
Published Version
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