The Study On Glass Forming Ability And Plastic Deformation Characteristics Of Amorphous Alloys

Amorphous alloys have attracted considerable interests of researchers owing to their unique structural characteristics,low modulus of elasticity,superplasticity,excellent corrosion resistance,high hardness,and high strength.Thus they have a extensive application in sports,electricity,aerospace and defense.However,poor glass forming ability(GFA)and plastic deformation capacity greatly hinder their practical applicability.The study of GFA and plastic deformation capacity is of great significance for better understanding the nature of glass transition,uncovering the origin of shear strain,but also for improving the plasticity and the GFA of amorphous alloys.It is focused on investigating the numerical relation between fragility and critical cooling rate as well as Poisson's ratio in this paper,and finally reveals the correlation among fragility,glass forming ability and plastic deformation ability.The main research works and innovative results are summarized as follows:(1)By studying influence of thermodynamic and kinetic factors on the glass forming ability of amorphous alloys,it has been found that GFA is positively correlated to reduced glass transition temperature but inversely proportional to fragility.Based on this,a new criterion is proposed to characterize GFA,and the rationality and superiority of this criterion are confirmed by using the linear fitting functions.It can be concluded that the multi-component alloy system with large atomic size difference has better GFA than the low-component alloy system through discussing the relationship among component number,reduced glass transition temperature and fragility,which provides a theoretical basis for the development of novel amorphous alloys.(2)By combining theoretical derivation and numerical analysis,the correlation between fragility and poisson's ratio has been systematically studied.And then a quantitative relationship(v=0.7-22/(0.4m?42)or v=0.2751g(m)-0·121)has been proposed,which shows that there is a positive correlation between fragility and plastic deformation ability.The fragility value reflects the amount of free volume that is 'inherited' during the formation of the amorphous alloys,and the amount of plastic deformation extremely depends on the original free volune.Based on the free volume model and the shear transition zone model,the study of the deformation process of amorphous alloys found that the amount of free volume is positively correlated with the plastic deformation capacity when it is widely distributed but that the amount and the capacity exhibits the opposite trend under the condition of concentrated distribution.Accordingly,it is proposed to inject uniformly distributed free volume or other heterogeneity such as second phase particles and dendritic solid solution into the amorphous alloy body as an effective measure for improving the plastic deformation capacity of the amorphous alloy.(3)The relation among fragility,component number,critical cooling rate and poisson's ratio was studied by statistical analysis.It has been found that amorphous alloys satisfies that the larger the number of components,the better the glass forming ability but the worse the plastic deformation ability.On the other hand,as the fragility value increases,the glass forming ability of the amorphous alloy decreases,but the plastic deformation ability shows an increasing trend.That is to say,there is a mutual restriction between the GFA and the plastic deformation ability of the amorphous alloy.