Novel TiCuNiCo composites with high fracture strength and plasticity

Ti60Cu30Ni10−xCox (x = 0, 2, and 4) alloys with high fracture strength and large compressive plasticity have been investigated. The microstructure and fracture morphologies have been studied by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The largest compressive fracture plastic strain of 32.5% with the fracture strength of 2480 MPa is achieved for Ti60Cu30Ni10Co4 alloy composite. The enhanced plasticity is attributed to the addition of Co element having a positive heat of mixing with Cu element, and the retardment for the shear band propagation resulted from the dendrites, which are homogeneously distributed in the matrix. The high fracture strength of the alloys is resulted from work hardening character due to a series of dislocations in the dendrites and the unique microstructure of the Ti60Cu30Ni10Co4 alloy, i.e., the coexistence of amorphous phase, nanocrystals, and micron-scale dendrites.

► Co is selected as additional element to TiCuNi alloy system. ► Increasing Co content will increase the strength and plasticity of the composite. ► Clear “work-hardening” feature is observed in the studied composites. ► The large plasticity is related to the positive heat of mixing between Co and Cu.