Tensile and fatigue behaviour of Ni–Ni₃Si eutectic in situ composites

A Ni–Ni₃Si composite was fabricated via a eutectic reaction (Ni–Ni₃Si) using a rapidly cooled directional solidification technique at a solidification rate of 40 μm s⁻¹. The composite consisted of approximately 62.2% Ni–Si solid solution and 37.8% Ni–Ni₃Si eutectic phase in volume. Four-point bend fatigue tests were carried out on the composite. The fatigue strength of the alloy was measured to be 520 MPa (maximum cyclic stress). It was found that the fatigue cracks were preferably initiated in the Ni–Ni₃Si eutectic phase, and that the Ni matrix was fractured in a cleavage fashion. It was probably attributed to the high level of supersaturated Si in the Ni matrix, which led to inducing the embrittlement of the Ni matrix.