| In this work, Ti40Zr25Ni3Cu12Be20and Zr55Cu30Ni5Al10(at.%) bulk metallicglasses (BMGs) have been prepared and treated by electropulsing. The effect ofelectropulsing treatment (EPT) on the microstructure and mechanical properties ofBMGs have been systematically studied. The electropulsing processing parametershave been also optimized.The microstructure of as-cast and EPTed Ti-based and Zr-based BMG sampleshas been investigated by using synchrotron radiation, X-ray diffraction(XRD),scanning electron microscopy(SEM), and transmission electron microcopy (TEM).The calculation results of the autocorrelation function(ACF) of high-resolutionTEM(HRTEM) images indicated that, with increasing the applied voltage, the orderdegree of both Ti-based and Zr-based BMGs gradually increases, whereas the sizeof fluid-like flow units firstly increase and then decreases, yielding a largest valuewhen the order degress reaches~15%. When the applied voltage is larger than3900V, Ti-based BMGs will crystallize. For Zr-based BMG, no samples crystallizein this work. The synchrotron radiation results demonstrated that, with increasingthe applied voltage, both Zr-based and Ti-based BMGs possessed smaller atomicdistance, indicating that the BMGs exhibited denser atomic configuration after EPT.Thermal properties of two BMGs before and after EPT have been studied. Bothglass transition temperature (Tg) and the activation energy of glass trasformation(Eg) increase after EPT. It means that EPT will induce the structure relaxation ofBMGs and increase their thermal stability.The room temperature compressive tests of BMG samples have beenperformed before and after EPT. Proper voltage of EPT could remarkably increasethe deformation capacity of BMGs. For Ti-based BMG, plastic strain increases from0.9%for as-cast sample to7.6%for3000V EPTed BMG sample. For Zr-basedBMG, plastic strain increases from near zero for as-cast sample to2.53%for3600V EPTed sample. The enhanced plasticity can be attributed to the increase ofthe size of flow units at proper EPT voltageNanomechanical behaviors of BMGs before and after EPT have been detectedby using nanoindentation. After EPT at proper voltage, the load of first pop-inenvent decreases and the number of pop-in events on their load-displacement (p-h)curves increases. This suggested that during nanoindentation, shear bands can easilynucleate within BMG samples EPTed at proper voltage. |
