Fabrication and toughening of NbCr2 matrix composites alloyed with Ni obtained by powder metallurgy

NbCr2 Laves phase intermetallics with or without Ni were successfully synthesized by mechanical alloying (MA) and hot pressing (HP) techniques. The mechanical alloyed powders were vacuum hot-pressed at 1250 deg C for 0.5 h. The fracture toughness at room temperature was measured by Anstis' mode and the responded microstructures were analyzed by using scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The results show that the addition of Ni could obviously toughen the matrix. When the content of Ni in NbCr2 is about 5 at.%, the fracture toughness value increases by about 30% more than that of pure NbCr2. The corresponding toughening mechanisms depend on the following: Ni replacing Cr, solid solution toughening, fine-grain, crack deflection, crack microbridging, crack bowing and branching.