Study On Fracture Behavior For Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 Bulk Metallic Glasses Under Impact Loading

Based on the modified Split Hopkinson Pressure Bar?SHPB?device,the single edge notched-three point bending test for Zr_41.2Ti_13.8Cu₁₀Ni_12.5Be_22.5?Vit 1?bulk metallic glass?BMG?was carried out.The sensitivity of the mode I/III dynamic notch toughness?K_Q^d?to the loading rate was studied.Different from a mode I fracture,a disordered vein-like pattern was found in the fracture surface under the mode I/III condition,indicating the existence of a complex stress state.The complex stress state is considered to promote the generation of denser shear bands.Quantitative analysis revealed that the shear band number?N_s?increased and the spacing between the primary shear bands???decreased with the increasing loading rate.A power law relationship,K_Q^d=C₁?N_S?^0.5,was noted with K_Q^d and N_s,which was similar for various BMGs under the quasi-static loading condition,and?also showed an excellent power law correlation,_QK^d=C₂?l?^0.35,withK_Q^d.The shear band might act as a bridge between the dynamic notch toughness and loading rate.Moreover,based on the theory of self-organized criticality?SOC?,additional shear bands and a smaller spacing between the primary shear bands enhance the interactions of the shear bands,which can buffer large changes,resulting in an effect on the dynamic notch toughness.The difference of fracture behavior between BMGs with mode I/III notch and BMGs with mode I notch is found.By comparing with mode I fracture,it is found that crack initiation time of Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 BMG under mode I/III fracture are obviously delayed under impact loading.And the unloading process in mode I/III fracture is obviously hindered.The peak load acting on Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 BMG was found to increase with the increasing impact velocity.The mode I/III fracture bears a greater peak load than mode I fracture under similar impact velocity.Through an analysis of SEM for specimen,experimental results are explained from shear band formation mechanism and morphology.The finite element method of dynamic three-point bend experiment for Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 BMG was carried out by Abaqus.The load-time curve,displacement-time curve and stress distribution diagram of specimens under the impact velocity of 20m/s were obtained.Compared with the experimental results,the validity of the model is verified.The stress distribution at the notch of the two kinds of specimens was found to be consistent with the crack initiation position and propagation path in the experiment.It is proved that both mode I fracture and mode I/III fracture of zr41.2ti13.8cu12.5ni10be22.5 BMGs are driven by stress.