Study On The Relationship Between Cooling Rate,Sample Location And Zr-based Amorphous Mechanical Properties Based On High Rheological Rate Forming (HRRF)

Metallic glass has been widely concerned for its excellent mechanical and physical and chemical properties.However,the brittleness and forming difficulty of bulk metallic glass(BMGs)greatly limit its practical application.To overcome these two application bottlenecks,the author's team invented the high rheological rate forming(HRRF)method.The method can be used to form BMGs components in a time of 20 ms,and improve its plasticity effectively at the same time.In order to further improve the method,this paper takes amorphous alloys such as Zr57Cu20Ni8Al10Ag5 are mainly studied,the influence and rule of different HRRF process conditions and forming component factors on mechanical properties and distribution were deeply explored.It mainly includes the effect of mold cooling rate,component size,radial and height position on the plasticity and microhardness of BMGs samples after molding.In addition,the intrinsic physical nature of the macroscopic performance change is revealed through DSC's exothermic enthalpy,density,fracture morphology and other differences.The main research results are as follows.1.By adjusting the cooling rate of the molds,the experimental results show that the compression plasticity of the amorphous sample after high rheological molding is obviously higher than that of the suction cast amorphous sample under the same cooling rate.The validity of HRRF plasticizing method was verified.With the increase of cooling rate,the compression plasticity of both the traditional cast formed sample and the amorphous sample after HRRF increases with the cooling rate.It is especially worth emphasizing that the plasticity of the HRRF samples increases with the cooling rate higher than that of the as-cast samples.The microhardness of HRRF formed samples is lower than that of suction-cast amorphous samples,The decrease rate decreases with the increase of cooling rate.2.SEM fracture reveals that,with the increase of cooling rate,the vein-like veins in the fracture of samples after high rheological molding keep increasing.It is suggested that the density of shear banding increases with the cooling rate,which is consistent with the increase of plasticity.DSC analysis data showed that the increase of cooling rate significantly increased the exothermic enthalpy of amorphous samples formed by HRRF and cast It is revealed that the free volume increase in amorphous structure is in good agreement with the results of density analysis.On the other hand,the HRRF molding process introduced more free volume into the amorphous than that of the traditional suction casting forming.3.It is found that the compression plasticity of HRRF formed amorphous specimen is obviously higher than that of as-cast amorphous sample.Among them,the compression plasticity of amorphous samples formed by HRRF decreases with the change of height;SEM fracture analysis revealed that the density of vein-like veins at the top,middle and bottom three positions was the same as the plastic variation trend.DSC analysis shows that the free volume of the lower amorphous structure is the largest and the upper is the smallest.4.The analysis of samples intercepted from different radial positions of the amorphous samples after HRRF shows that with the change of radial position,the plasticity of amorphous increases gradually from inside to outside,the change rule of microhardness is opposite.The changes of vein-like veins in SEM fracture were consistent with the plasticity.This paper reveals the distribution and rule of mechanical properties of amorphous components after HRRF,which provides a technical basis for the practical application of the method and enriches the basic science of amorphous field.