Enhanced mechanical properties of NbCr2 Laves phase by spark plasma sintering

•Bulk NbCr2 Laves phase alloy was successfully fabricated by vacuum sinter.•Small amounts of Cr solid solution and Nb solid solution occurred in the microstructure.•An explanation on the formation of the Cr solid solution and Nb solid solution is proposed.•The Cr and Nb solid solutions can enhance the fracture toughness of NbCr2 Laves phase.

Bulk NbCr2 Laves phase with improved mechanical properties was successfully fabricated by spark plasma sintering (SPS). The hardness of the SPS-processed NbCr2 Laves phase measured by a Berkovich nanoindenter operated with the continuous stiffness measurements (CSM) mode attains 14.35 ± 0.53 GPa, which is increased by about 63% over the as-cast NbCr2 Laves phase. More importantly, the room-temperature fracture toughness of the SPS-processed NbCr2 Laves phase is increased to 6.7 MPa m1/2, which is 5.6 times higher than that of the as-cast NbCr2 Laves phase (1.2 MPa m1/2). The microstructure analysis indicates that during the SPS process, the grain size of NbCr2 Laves phase is significantly refined and trace amounts of Nb and Cr solid solutions are observed to distribute among the grain boundaries. In this condition, the remarkable enhancement in hardness and fracture toughness of the SPS-processed NbCr2 Laves phase is attributable to fine grain toughening and dual ductile phase toughening, which can bear large deformation to absorb the crack energy and resulted into substantial increases in the hardness and fracture toughness of the NbCr2 Laves phase matrix. In addition, the formation mechanism of the Nb and Cr solid solutions during the SPS is discussed in terms of the intrinsic characteristics of NbCr2 Laves phase and the unique atomic diffusion under pulsed current during the SPS.