Microstructure evolution and mechanical properties of intermetallic Ni–xSi (x = 5, 10, 15, 20) alloys

In this study, the microstructure and mechanical properties of conventionally solidified Ni–xSi (x = 5, 10, 15, 20) alloys were investigated. The microstructures of the Ni–Si alloys were characterized by SEM and the phase composition was identified by XRD analysis. The phase transition during the solidification process was studied by DTA under an Ar atmosphere. The results show that the microstructure and solidification behavior are closely related to the composition of Ni–Si alloys. The hardness and tensile strength of specimens at room temperature were examined. The tensile properties of the Ni–Si alloys were also improved and the alloy containing 20 wt.% Si exhibited the highest tensile strength. Experimental results showed that the mechanical properties of Ni–Si alloys were enhanced, which can be attributed to significant changes in the microstructure. Vickers micro-indentation tests were performed on the samples with different peak loads at room temperature. It was found that the hardness and effective elastic modulus values increased with Si-addition and these values showed peak load dependence.

► The solidification behavior is closely related to the composition of Ni–Si alloys.
► The α-Ni phase is the stable phase for these compositions.
► Si contends for Ni–Si alloys have a strong impact on the microstructural evolution.
► The strengthening effect is enhanced with the increasing of Si content.
► Hardness and elastic modulus values of the samples were obviously load depended.