Effects And Differences Of Annealing And Annealing With Pressure On The Rejuvenation Of Cu₅₀Zr₅₀

Because of the special disordered structure,excellent performance and wide application prospects,metallic glass has attracted much attention.However,its spontaneous aging leads to deterioration of properties.Rejuvenation is an effective structural excitation method to deal with aging,which can restore the high energy state and excellent properties of metallic glass,by inputting external energy.However,the current research on the rejuvenation of metallic glass mainly focuses on how to obtain the rejuvenated metallic glass,the improving of mechanical properties and microscopic reasons for its rejuvenation are rarely explored.In this paper,molecular dynamics simulation was used to explore effects of annealing and annealing with pressure on the rejuvenation of Cu₅₀Zr₅₀metallic glass,and the influence of annealing temperature,annealing rate and load pressure during the annealing process on the microstructure of metallic glass.The influence of the change of microstructure on the rejuvenation was discussed.The main work and conclusions of this paper are as followed:(1)The effects of different annealing temperatures on the rejuvenation and aging of Cu₅₀Zr₅₀metallic glass were investigated when the annealing rate was 10¹²K/s.It was found that the metallic glass samples did not get rejuvenated at this cooling rate,but aged,and the sample was the most seriously aged when the annealing temperature was around the glass transition temperature.The aged metallic glass samples have low,energy state,poor plasticity and increased density.The fraction of densely packed polyhedron<0,0,12,0>and<0,2,8,5>increased,and the fraction of loosely packed polyhedron<0,3,6,4>and<0,2,8,1>decreased.(2)The effects of different cooling rates during annealing on the rejuvenation and aging of Cu₅₀Zr₅₀metallic glass was investigated.It was found that the lower annealing rate could not make the metallic glass samples rejuvenated.When the annealing rates were at 10¹³K/s and 10¹⁴K/s with the annealing temperature exceeded the melting temperature,the metallic glass samples would get rejuvenate.The Zr-centered structure of the metallic glass get stimulated through annealing treatment,which made the samples come into being more free volume that causes the increase of energy,better plasticity and smaller density of the metallic glass sample.All above is the reason why metallic glass get rejuvenate after high cooling rate and temperature annealing.(3)The effect of different pressures on the rejuvenation and aging of Cu₅₀Zr₅₀metallic glass during annealing was investigated.It was found that when annealing was carried out around the glass transition temperature and the load pressure was more than 20 GPa,the metallic glass got rejuvenated.The rejuvenated metallic glass is mainly excited by the Cu-centered structure inside the metallic glass through annealing thermal-pressure treatment,which causes more negative free volume and leads to the increase of the energy of the metallic glass sample,better plasticity and higher density.All above is the reason why metallic glass get rejuvenate after high pressure annealing treatment.