Study On The Preparation And Thermoplastic Forming Technique Of Zr-based Bulk Metallic Glasses

Bulk metallic glass?BMG?,also known as bulk amorphous alloy?BAA?,is a new class of advanced material with a series of excellent properties,thus making it attract attention of scientists over the world.In this paper,we choose Zr₅₇Nb₅Cu_15.4Ni_12.6Al₁₀?Zr₅₅Ti₂Nb₅Cu_15.4Ni_12.6Al₁₀?Zr_41.2Ti_13.8Cu_12.5Ni₁0Be_22.5?Zr₆₄Nb₃Cu₁₇Ni₆Al₁₀?Zr₃₅Ti₃₀Be_27.5Cu_7.5 fabricated with the copper mold casting to investigate their mechanical performance at room temperature and glass forming ability?GFA?.Also we have made the comparison of crystallization kinetics and thermal stability among the five BMG systems and established the processing windows for thermoplastic forming.In addition,we choose as-cast Zr₃₅Ti₃₀Be_27.5Cu_7.5 with wide SCLR as our specimen and make research of the rheological law and characteristics of microstructures after thermal compression.Under the optimal parameters we have experimentally found out,we conduct the thermoplastic imprinting and joining.Results indicate that:all of the five kinds of metallic glasses with the diameter of 6 mm prepared by us have complete amorphous structures and have good mechanical performance;among them,Zr₃₅Ti₃₀Be_27.5Cu_7.5 with lowest Tg value has the largest ?T,S,?T/Tg,? and KH,showing that this system has great glass forming ability and thermoplastic formability as well;according to DSC curves,we have found out that all the characteristic temperatures will move up towards the high-temperature region with the heating rate increasing,and the width of SCLR will be larger as well,which shows significant kinetic effect;we adopt several parameters?Tg,?T,KH,Tx,Ekissinger,EOzawa,K0,?Hx and ?Hm?to characterize the thermal stability of the five BMGs,the results will differ according to different parameters and Zr₃₅Ti₃₀Be_27.5Cu_7.5 exhibits the strongest thermal stability and largest crystallization enthalpy;according to the transformed Kissinger equation,we have fitted continuous heating transformation?CHT?curves of the five systems and found out that the processing time-temperature window for Zr35Ti30Be27.5Cu7 5 is largest;Besides,we have performed the isothermal hot compression in Zr₃₅Ti₃₀Be_27.5Cu_7.5 BMG system at 370?,390? and 410?,respectively,finding out that the rheological law in as-cast Zr₃₅Ti₃₀Be_27.5Cu_7.5 BMG system will change greatly with different temperatures in SCLR and strain rates;we also test the microstructures of the specimen after hot compression through XRD technology and we draw the conclusion that the deformation temperature cannot be too high and strain rate cannont be too low in order to suppress crystallization,and in order to reduce the deformation force,we cannot compress the system at relatively low temperature and high strain rate.Under the condition of?390?,5×10-3s-1?,we have successfully conducted the hot imprinting and joining in as-cast Zr₃₅Ti₃₀Be_27.5Cu_7.5 BMG system,obtaining the complete duplication surface,the distinguishable and clear morphology texture and tight interface joint.