Study On Ultrasonic Assisted Extrusion Process Of Zr-based Bulk Metallic Glass

With the increasing application of miniature components in the fields of electronics,communications,and micro-electromechanical systems,the forming process of micro parts has received extensive attention.Micro-plastic forming technology has become one of the key technologies for the manufacture of miniature parts because of its advantages of high precision,high production efficiency,low cost,and net forming.Bulk metallic glasses（BMGs）,with their unique amorphous structure,can avoid grain size effects during the microforming process and possess excellent plastic forming ability in the supercooled liquid region.Therefore,amorphous alloys have broad application prospects in the field of microplastic forming.In the current BMGs micro-plastic forming process,there are still problems such as poor micro-fillability and large contact friction of amorphous alloy materials,which directly affect the micro-forming ability of amorphous alloys.In order to improve the micro-forming properties of amorphous alloys,ultrasonic vibration was introduced into the amorphous alloy forming process.The Zr₃₅Ti₁₀Cu_26.75Be_8.25 bulk amorphous alloy was used as the object of study.Ultrasound-assisted uniaxial compression and micro-extrusion of amorphous alloys were studied.The pressure process was used for the forming test to study the uniaxial compression plastic deformation characteristics of the amorphous alloy in the supercooled liquid region and the plastic forming characteristics of the die extrusion molding.The ABAQUS finite element software was used to simulate the forming process to analyze the mechanism of ultrasonic vibration on the extrusion process of BMGs.The study is as follows:1.The Zr₃₅Ti₁₀Cu_26.75Be_8.25 BMG rod with a diameter of 3mm was prepared by acopper mold suction casting method.The temperature range of the supercooled liquid zone was determined to be 308-456°C.Using the principle of overall removal and placement of the mold,design the micro-extrusion forming mold.The ultrasonic vibration system was built using the ultrasonic vibration platform developed by the research group.The test results show that the overall resonance frequency of the ultrasonic vibration system is 19969.3Hz,which can achieve stable ultrasonic vibration loading and meet the test design requirements.2.Ultrasound-assisted uniaxial compression forming tests of amorphous alloy specimens under different ultrasonic power output,supercooling temperature and extrusion speed were performed to obtain the corresponding true stress-true strain curve and the maximum stress of the uniaxial compression of the amorphous alloy.,final forming area and forming height.The results showed that:（1）When the cold temperature increases and the extrusion speed decreases,the flow stress of the material in the uniaxial compression process gradually decreases,the extrusion forming area increases sequentially,and the height gradually decreases.When the ultrasonic power output is 40%,the forming temperature is 380°C,and the extrusion speed is 0.12mm/min,the flow stress of the amorphous alloy is reduced by32.8%,the area of the formed part is increased by 55.6%,and the forming height is reduced by 50.0%.（2）At a forming temperature of 380°C and an extrusion speed of 0.24 mm/min,when the ultrasonic power output increases from zero to 60%,the maximum flow stress is reduced by 57.8%and the extrusion area is increased by 266.1%.This indicates that With the increase of the ultrasonic amplitude of the tool,the plastic forming ability of the amorphous alloy is improved;the uniaxial compression process and the stretching process under different ultrasonic amplitudes are simulated by ABAQUS and it is found that the ultrasonic vibration can be accelerated compared with the conventional compression process.The rheological rate of the amorphous alloy in the forming process increases the free volume concentration and reduces the viscosity,so that the plastic deformation of the amorphous alloy is easier.3.Ultrasonic-assisted microextrusion of different ultrasonic power output,supercooling temperature and extrusion speed for amorphous alloy specimens was performed.And the corresponding true stress-true strain curves and micro-extruded lengths of the amorphous alloy specimens were obtained.And the corresponding equivalent fill length is calculated.The results showed that:（1）At a forming temperature of 380°C and an extrusion speed of 0.24 mm/min,when the ultrasonic power output increases from 0 to 60%,the maximum stress decreases by 60.17%,and the equivalent filling length of the sample increases by810.9%.This shows that the greater the ultrasonic amplitude of the tool,the more pronounced the ultrasonic softening effect,and the more remarkable the micro-forming ability of the amorphous alloy.At the same time,using ABAQUS to simulate and analyze the micro-extrusion process under different ultrasonic amplitudes,it was found that the application of auxiliary ultrasonic vibration can also reduce the equivalent friction coefficient of the forming process.（2）With the increase of the micro-extrusion forming temperature and the decrease of the extrusion speed,the forming flow stress of the amorphous alloy gradually decreases,and the equivalent filling length of the sample increases.When the ultrasonic output power is 40%,the forming temperature is 380°C and the extrusion speed is 0.12mm/min,the extrusion flow stress of the amorphous alloy is decreased by 31.88%,and the equivalent filling length of the sample is increased by 264.2%.（3）The study also shows that increasing the forming temperature and loading the ultrasonic vibration can enhance the amorphous alloy in the micro-extrusion forming ability,but the ultrasonic vibration can get relatively better improvement.（4）The ABAQUS was used to optimize the process parameters of the amorphous alloy micro-extrusion process.The results show that when the ultrasonic vibration frequency is 60kHz,the contact surface friction coefficient is between 0 and 0.1,the supercooled forming temperature is 380°C,and the extrusion speed When0.12mm/min and ultrasonic amplitude is 24μm,better softening effect of ultrasonic and micro-extrusion quality of amorphous alloy can be obtained.