Fabrication Of Bulk Metallic Glasses And The Mechanism By High Frequency Ultrasonic Beating

Amorphous alloy is a kind of metastable metallic material,in which the atoms lose the long-term order and maintain the short-term order in the three-dimensional space when the metal melts are frozen rapidly under the condition of rapid cooling.Compared with traditional metal,amorphous alloy is a new type of fluid-like material at the microscopic scale.Due to amorphous alloys combine the unique physical,chemical and mechanical properties of metals and glasses benefiting from the absence of crystalline defects such as dislocation and grain boundary,it has attracted extensive concern in the scientific and industrial,which becomes one of the most active materials in the field of materials and physics.However,the traditional methods of preparing amorphous alloys requires a large cooling rate,which can't fundamentally solve the major problem of insufficient-size,and becomes a long standing issue for their engineering applications.Therefore,the critical challenge in this field is to overcome the glass forming ability and develop efficient fabrication technique.To address this challenge,new methods such as thermodynamics-based alloy design,3D printing and artificial intelligence guided alloy design have emerged based on the traditional preparation methods and connection technologies of amorphous alloys.This paper proposes a simple and effective new fabrication method is proposed for bulk amorphous alloys without an external heat source--the high frequency ultrasonic beating method,basing on the ultrasonic plasticization technique.The ultrasonic welding head with high power transfer efficiency and frequency coupling was designed and manufactured according to the requirements of vibration frequency and working condition in the experiment,and a self-designed amorphous alloy preparation mold was built on the platform of the ultrasonic welding equipment.The effects of parameters such as amorphous ribbons size,welding energy,vibration time and welding pressure on the forming quality of amorphous alloys prepared by the high frequency ultrasonic beating were also analyzed in this paper.Single-phase and multi-matrix composite amorphous alloys without appearance defects such as pores and cracks and without crystal transformation were prepared successfully.A series of studies on the density,hardness and mechanical properties of bulk amorphous alloys prepared by the high frequency ultrasonic beating were carried out by using copper die suction casting amorphous bar as a control.The results show that there is no essential difference between the properties of bulk amorphous alloys and the control samples.On the basis of the intrinsic structure and performance test,this paper reveals the principle of high frequency ultrasonic vibration compacting the bulk amorphous alloy,and analyzes the interaction mechanism between the inhomogeneous structure of the amorphous alloy and the high-frequency ultrasonic beating.High-frequency dynamic loading fully activates the stress relaxation within the ultrathin surface layer,accelerates the internal atomic migration,and the stress superposition and softening effect enable the interface of the amorphous alloy ribbon to reach a state where the atomic spacing can bond at a temperature far below the glass transition point,until the atomic bonding forms a tight connection.In principle,the proposed technique evades the glass forming limit of the amorphous alloy,and has no size restrict faced by the traditional method,which provides a new ideas for the fabrication of bulk composite amorphous alloy with different properties from the composition,phase and shape design,it can promote the deeper scientific research and extend considerably the application scope of this new type of metallic materials.