| Amorphous alloys are widely used in many fields because of their excellent mechanical,physical and chemical properties.Therefore,the development of bulk amorphous alloys is seriously restricted.The existing research shows that the thickness of shear band formed in amorphous alloy is about 1020 nm,which is much smaller than that of traditional metal material（10500μm）.The great difference in the thickness of shear bands indicates that the formation mechanism of shear bands in amorphous alloys is difficult to be explained by the thermal softening mechanism in traditional metallic materials,and may be associated with the unique atoms of amorphous alloys.Structure（free volume）related.In order to understand the role of free volume in the formation of shear bands in amorphous alloys,the following studies were carried out:（1）A three-dimensional cutting model of Cu50Zr50 amorphous alloy was established by means of molecular dynamics simulation,and a group of orthogonal cutting experiments with five factors and four levels were carried out.The effects of tool geometry and cutting parameters on the free volume in the shear deformation zone and the machined surface were investigated.It is found that the blunt circle radius has the greatest influence on the free volume content in the shear deformation area,and the cutting speed in the machined surface area has the greatest influence on the free volume,and the free volume in both regions decreases with the increase of the tool blunt circle radius.However,with the increase of cutting speed,the free volume content in the machined surface increased obviously,but there was no free volume content in the shear deformation zone.There is obvious trend of change.（2）the evolution process of free volume in cutting process of amorphous alloy is analyzed.It is found that in the initial stage of cutting,the increase of main cutting force will reduce the free volume,but once the chip is formed,the free volume will increase abruptly.It then increases and decreases periodically in the shear deformation zone.The free volume of the machined surface will change violently when the cutting goes up,and the free volume of the machined surface will continue to increase.（3）in view of the fact that the free volume distribution in the cutting process can not be obtained by the traditional free volume algorithm,a method of calculating the free volume in the net format is proposed.The cloud diagram of free volume distribution in the cutting process of amorphous alloy can be obtained.According to the calculated cloud images,it is found that the larger the free volume concentration in the machined surface area is the important reason for the increase of the back force.（4）by analyzing the free volume variation curve in the shear deformation region and the main cutting force variation curve in the cutting process,the formation process of the shear band is observed according to the cloud map of the free volume distribution at each time.It is also found that the periodic aggregation of free volume in the shear deformation region is the main reason for the formation of shear bands. |
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