Crystallization kinetics and spark plasma sintering of amorphous Ni53Nb20Ti10Zr8Co6Ta3 powders prepared by mechanical alloying

Amorphous Ni53Nb20Ti10Zr8Co6Ta3 powders were successfully fabricated by mechanical alloying. The glass-forming ability and crystallization behavior of the synthesized alloy powders were investigated by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The non-isothermal crystallization kinetics were analyzed by the Johnson-Mehl-Avrami equation. The crystallization of the amorphous Ni53Nb20Ti10Zr8Co6Ta3 powders exhibits two distinct steps, and the values of the Avrami exponent n implies that the crystallization of the first and second steps are dominated by interface-controlled three-dimensional growth as well as the volume-diffusion-controlled two-dimensional growth, respectively. In addition, the bulk crystallized alloys consolidated from the amorphous powders by spark plasma sintering exhibit high fracture strength of 3169 MPa and ultra-high hardness of 1069 HV. The compressive fracture strength and fracture strain of the as sintered alloy at 1073 K reach 2020 MPa and 7.6%, respectively. (C) 2015 Elsevier Ltd. All rights reserved.