Microstructure of multilayer interface in an Al matrix composite reinforced by TiNi fiber

• The multilayer interface in TiNif/Al composite was studied by TEM.
• Three layers have been found: TiNi–B2 layer, Ti–Ni compounds layer and Ti–Al compounds layer.
• Ni5TiO7 phase was formed between TiAl3 and NiTi2 phase.
• The composite with excellent ductility exhibited typical ductile fracture pattern.

A multilayer interface was formed in the Al matrix composite which was reinforced by 30% volume fraction of TiNi fiber. The composite was fabricated by pressure infiltration process and the interface between the TiNi fiber and Al matrix was investigated by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). When the TiNi fiber was pre-oxidized in the air at 773 K for 1 h, three layers have been found and characterized in the interface: TiNi–B2 layer near the TiNi fiber, Ti–Al compound layer with Ti and granular TiO2 near the Al matrix, and Ti–Ni compound layer between TiNi–B2 and Ti–Al compound layers. The effect of the multilayer interface on the mechanical properties of the composite was also discussed. The result showed that the uniaxial tensile strength of the composite at room temperature was 318 MPa, which was very close to the theoretical calculation value of 326 MPa. Moreover, the composite with good ductility exhibited a typical ductile-fracture pattern.