Preparation And Crystallization Behaviors Of Co-based Amorphous Alloys Without Metalloid

The ribbons of Ni-Co-Nb-Ti、Co-Nb-Ti-M(M=Zr、Y、Hf、Mo、Ta、Fe) and Co-Zr-Ta-M(M=Nb、Y、Hf、Mo、Ti、Fe) alloy systems were prepared by melt-spun method. The glass formation ability (GFA) and the crystallization kinetics of the alloy systems were studied by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The results as follows:(1) With increasing content of Co from30to60at.%, the GFA of Ni-Co-Nb-Ti alloy systems was reduced. The results showed that the microstructure of Ni30Co30Nb25Ti15and Ni10Co50Nb25Ti15alloy ribbons were all amorphous phase. But the structure of Co60Nb25Ti15alloy ribbon consisted of amorphous phase and crystalline compound Nb1.08Co1.92.(2) The DSC curves of Ni3oCo3oNb25Ti15indicated the crystallization process undergoes one stage and showed an obviously dynamic effect. Its crystallization process was eutectic crystallization with multi-crystalline phases. The activation energy of the onset and peak of crystallization was165.7kJ/mol and168.4kJ/mol respectively.(3) The appropriate content of Zr and Y(5at.%)had improved the glasses forming ability of Co60Nb25Ti15alloy, but same content of Hf、Mo and Ta were exactly opposite. The system alloys of Co60Nb25-xTi15Zrx exists a narrow amorphous forming regime, in at.%,0<x<5with cast amorphous alloys ribbons.(4) The crystallization process of Co60Nb20Ti15Zr5amorphous ribbons undergoes one stage and the Co60Nb20Ti15Y5undergoes two stages. They all had obvious dynamic effect and had same crystallization behavior. The activation energy of the onset and peak of crystalization of Co60Nb20Ti15Zr5was149.5kJ/mol、126.2kJ/mol respectively. The crystallization activation energy of Co60Nb20Ti15Y5as follows:Exl=474kJ/mol、 Epl=332.5kJ/mol; Ex2=727kJ/mol、Ep2=344.6kJ/mol.(5) A ternary Co-Zr-Ta alloy systems existed a narrow amorphous forming regime, in at.%,50<Co<55and40<Zr<35with cast amorphous alloys ribbons. The subsequent addition of appropriate amounts(10%) of Nb、Y and Ti to Co50Zr30Ta20alloy respectively resulting in the improvement of GFA, while Hf、Mo and Ta addition deteriorated the GFA. The range of parameter x in quaternary Co60Zr30-xNbxTa10alloys system is from10to20at.%。(6) The crystallization process of Co60Zr20Nb10Ta10amorphous ribbon undergoes two stages. And this alloy had an obvious dynamic effect. The crystallization activation energy of Co60Zr20Nb10Ta10as follows:Exl=167.9kJ/mol、Epl=158.4kJ/mol; Ex2=315.5kJ/mol、Ep2=244.6kJ/mol.(7) The alloy systems of Co60-xFexNb2oTi,5Zr5(x=10,20,30; at.%) and Co50Fe10Zr20Nb10Ta10alloy ribbon were fail to forming the amorphous.It turned out that the addition of Fe deteriorated the GFA.