The Research on Forming Ability and Crystallization Behavior of (Cu50Zr42Al8)100-xYx Bulk Amorphous Alloy
|School||Lanzhou University of Technology|
|Keywords||Cu-based bulk amorphous alloy REE Y glass-forming ability thermal stability thermal crystallization isothermal crystallizatio|
The rod shape with diameters 3mm of bulk metallic glasses（BMGs） that atom percentage is (Cu50Zr42Al8)100-xYx （x=0,1,3,4,5） were prepared by using magnetic-suspending melting alloy ingots and copper-mold casting . By demarcating with X-ray diffraction （XRD）, there is main amorphous structure except Cu10Zr7. The analysis by differential scanning calorimetry （DSC） indicates that the thermal stability and the glass forming ability of Cu50Zr42Al8 has been enhanced with the affiliating of REE Y .It is calculated that the glass transition activation energy （Eg） of the three sample is 417.19KJ/mol、403.4KJ/mol、512.34KJ/mol, the activation crystallization energy（Ex） is 332.18KJ/mol、304.5KJ/mol、372.44KJ/mol, and the activation crystallization apex energy （Ep） is 327.70KJ/mol、360.5KJ/mol、404.5KJ/mol by non-isothermal crystallization analysis of amorphous alloy (Cu50Zr42Al8)100-xYx （x=0,3,4）. When the velocity of ascending temperature quicken, Tg、Tx、Tp will excursion to the field of high temperature and the three sample show the obvious kinetics Mechanical property . By calculating the activation phase crystallization energy of the three sample , found the activation phases crystallization energy of (Cu50Zr42Al8)96Y4 is higher than Cu50ZR42Al8’s. The activation phases crystallization energy of (Cu50Zr42Al8)97Y3 is smaller than Cu50Zr42Al8’s, when the percentage of crystallization is less than 50%,because there is crystal that is exist in the former and can become into the particle of forming crystal. The difference of activation phases crystallization energy of (Cu50Zr42Al8)97Y3 and Cu50Zr42Al8 is not too much, when the percentage of crystallization is more than 50%.Placing the sample of Cu50Zr42Al8 in the DSC equipment, then ascending temperature to the 753K、773K that are in the between of Tg-Tx and to 793k、813K、833K that are higher than Tx for isothermal annealing 30min . It were found that the five annealing sample both show the different extent crystallization and Cu10Zr7 and CuZr3 is the main crystal by using XRD and WDS.Ascending the temperature of Vacuum tube annealing equipment to 657K that is lower than Tg、to 697K、737K that are in the between of Tg-Tx and to 777K、817K that are higher than Tx for isothermal annealing for 30min . X-ray diffraction （XRD） was used to study these samples. The results present that there are no obvious crystallization in the former three samples. These samples were compared with Cu50Zr42Al8 that have experienced the isothermal annealing temperature that is lower than Tx. It was found that structural relaxation can be a important influence on the crystallization of amorphous alloy. Namely when the isothermal annealing is processed in the below of Tx ,if time relaxation is enough, amorphous alloy also can present crystallization. The two sample that were annealed in 777K、817K were analyzed by XRD and WDS. The results are found that the sample present obvious crystallization and the amount of crystallization increase when the temperature of isothermal annealing that is higher than Tx enhance. The Cu10Zr7 and CuAl2 is the main crystal.