Effect Of Nb Content On Thermal Stability And Bending Plasticity Of Zr-based Amorphous Alloys

Amorphous alloys have a wide range of applications due to their excellent mechanical,physical and chemical properties.However,since it is thermodynamically metastable,it is unstable at room temperature and has little macroplasticity,which limits its application in various aspects,so it is necessary to improve its thermal stability and room temperature plasticity.In this paper,Zr₅₅Al₁₀Ni₅Cu₃₀bulk amorphous alloy was used as the research object to study the influence of different content of Nb on its thermal stability and bending plasticity.In this paper,the sheet samples of(Zr₅₅Al₁₀Ni₅Cu₃₀)_100-xNb_x?x=0,1,3,5,7?alloy with a thickness of 1 mm were prepared by copper die casting method,and their structure were characterized by XRD.The continuous heating experiments of the alloy at different heating rates and the isothermal experiments at different temperatures were carried out by differential scanning calorimetry?DSC?;then the three-point bending experiments were carried out,and the fracture of the samples were observed by scanning electron microscopy.By analyzing and discussing the relevant experimental results,we got the following conclusions:(Zr₅₅Al₁₀Ni₅Cu₃₀)_100-xNb_x?x=0,1,3,5,7?bulk amorphous alloy under continuous heating conditions,with the increase of heating rate,its glass transition temperature T_g,crystallization begins Both the temperature T_xand the crystallization peak temperature T_pmove to the high temperature region,and the supercooled liquid phase region increases,and the glass transition and crystallization process of the amorphous alloy sample have dynamic characteristics.The addition of an appropriate amount of Nb can increase the glass transition activation energy of the amorphous alloy.When the content of Nb element is x=5,the alloy has the largest glass transition activation energy Eg=344.9 k J?mol-1,which has the best thermal stability and amorphous forming ability.The isothermal crystallization process of(Zr₅₅Al₁₀Ni₅Cu₃₀)_100-xNb_x?x=0,1,3,5,7?alloy is a three-dimensional growth process of diffusion control with increasing nucleation rate with time,and the addition of Nb element has no influence on the nucleation and growth mechanism of the crystal phase of Zr₅₅Al₁₀Ni₅Cu₃₀alloy.The addition of appropriate amount of Nb can increase the incubation time and crystallization peak width of Zr₅₅Al₁₀Ni₅Cu₃₀amorphous alloy,and reduce the reaction rate constant k and Avrami index n,improve the thermal stability of amorphous alloys and inhibit crystallization nucleation.When the content of Nb element reaches x=5,the alloy has the longest crystallization time,the widest crystallization peak and the lowest reaction rate constant k and Avrami index n,indicating that it has the best thermal stability.It can be known from the three-point bending experiment that as the Nb content increases,the maximum bending stress of the Zr₅₅Al₁₀Ni₅Cu₃₀bulk amorphous alloy increases gradually,that is,the bending strength increases,and the bending plasticity also increases.When the content of Nb element reaches x=7,the alloy has the maximum bending stress of 346.07 N and the maximum bending strength of 3893.26 Mpa.At the same time,the plastic deformation displacement of the alloy does not break when it reaches 3.70 mm,and has the best bending plasticity.