Dynamic strength behavior of Zr51Ti5NiloCu25A19 bulk metallic glass (BMG) up to 66 GPa was investigated in a series of plate impact shock-release and shock-reload experiments. Particle velocity profiles measured at ...Dynamic strength behavior of Zr51Ti5NiloCu25A19 bulk metallic glass (BMG) up to 66 GPa was investigated in a series of plate impact shock-release and shock-reload experiments. Particle velocity profiles measured at the sample/LiF window interface were used to estimate the shear stress, shear modulus, and yield stress in shocked BMG. Beyond confirm- ing the previously reported strain-softening of shear stress during the shock loading process for BMGs, it is also shown that the softened Zr-BMG still has a high shear modulus and can support large yield stress when released or reloaded from the shocked state, and both the shear modulus and the yield stress appear as strain-hardening behaviors. The work provides a much clearer picture of the strength behavior of BMGs under shock loading, which is useful to comprehensively understand the plastic deformation mechanisms of BMGs.展开更多
Room-temperature mechanical properties of Cu50Zr40Ti10-xNix(0≤x≤4,mole fraction,%) bulk metallic glasses (BMG) with aspect ratios in the range of 1:1-2.5:1 and loading rates in the range of1×10^-5-1×...Room-temperature mechanical properties of Cu50Zr40Ti10-xNix(0≤x≤4,mole fraction,%) bulk metallic glasses (BMG) with aspect ratios in the range of 1:1-2.5:1 and loading rates in the range of1×10^-5-1×10^-2s^-1were systematically investigated by room-temperatureuniaxialcompression test.In the condition of an aspect ratio of 1:1, the superplasticity can be clearly observed for Cu50Zr40Ti10BMG when the loading rate is1×10^-4s^-1, while for Cu50Zr40Ti10-xNix(x=1-3, mole fraction, %) BMGs when the loading rate is1×10^-2s^-1. The plastic strain (εp), yielding strength (σy) and fracture strength (σf) of the studied Cu-based BMGs significantly depend on the aspect ratio and the loading rate. In addition, theσyof the studied Cu-based BMGs with an aspect ratio of 1:1 is close to the σfof those with the other aspect ratios when the loading rate is1×10^-2s^-1. The mechanism for the mechanical response to the loading rate and the aspect ratiowas also discussed.展开更多
Dynamic response and damage evolution of Zr_(70)Cu_(13)Ni_(9.8)Al_(3.6)Nb_(3.4)Y_(0.2) bulk metallic glass(Zr-based BMG)under impact pressure ranging from 4.03 GPa to 27.22 GPa were studied.The Hugoniot Elastic Limit(...Dynamic response and damage evolution of Zr_(70)Cu_(13)Ni_(9.8)Al_(3.6)Nb_(3.4)Y_(0.2) bulk metallic glass(Zr-based BMG)under impact pressure ranging from 4.03 GPa to 27.22 GPa were studied.The Hugoniot Elastic Limit(HEL)and the spalling Strength(σ_(sp))were measured as 7.09 GPa and 2.28 GPa,and the curve of impact velocity(D)and particle velocity(u)were also obtained.Under the strain rate of~10^(5)s^(-1),local crystallization phenomenon was observed.As increasing the impact pressure,the failure mode of Zr-based BMG changed from spallation to fragmentation caused by the combination of spalling cracks and longitudinal cracks.Cone-cup structures were also observed in the internal spalling zone via nano-CT characterization.When increasing the impact pressure,the thickness of Zr-based BMG increased after impact and the remelting and cladding layers were also observed on the fracture surfaces.The fragments of the specimen were welded after impact due to the high temperature remelting,which causes plastic deformation of Zr-based BMG under shock loading.展开更多
The dynamic mechanical behaviors of hollow Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metal glass (BMG) are investigated using a splitting Hopkinson pressure bar (SHPB) in this study. Upon dynamic compressive loading, the ho...The dynamic mechanical behaviors of hollow Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metal glass (BMG) are investigated using a splitting Hopkinson pressure bar (SHPB) in this study. Upon dynamic compressive loading, the hollow specimen exhibit lower strength and poor ductility, caused by the higher stress concentration for the hollow one through FEM modeling. The different strain-rate responses for the hollow specimen are compared and explained. On the fracture surface of the hollow samples, there are highly dense vein patterns, many liquid drops and fishbone-like patterns.展开更多
The advanced fabrication of in-situ dendrite/metallic glass matrix (MGM) composites is reviewed. Herein, the semi- solid processing and Bridgman solidification are two methods, which can make the dendrites homogeneo...The advanced fabrication of in-situ dendrite/metallic glass matrix (MGM) composites is reviewed. Herein, the semi- solid processing and Bridgman solidification are two methods, which can make the dendrites homogeneously dispersed within the metallic glass matrix. Upon quasi-static compressive loading at room temperature, almost all the in-situ composites exhibit improved plasticity, due to the effective block to the fast propagation of shear bands. Upon quasi-static tensile loading at room temperature, although the composites possess tensile ductility, the inhomogeneous deformation and associated softening dominates. High volume-fractioned dendrites and network structures make in-situ composites distinguishingly plastic upon dynamic compression. In-situ composite exhibits high tensile strength and softening (necking) in the supercooled liquid region, since the presence of high volume-fractioned dendrites lowers the rheology of the viscous glass matrix at high temperatures. At cryogenic temperatures, a distinguishingly-increased maximum strength is available; however, a ductile-to-brittle transition seems to be present by lowering the temperature. Besides, improved tension-tension fatigue limit of 473 MPa and four-point-bending fatigue limit of 567 MPa are gained for Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 MGM composites. High volume-fraction dendrites within the glass matrix induce increased effectiveness on the blunting and propagating resistance of the fatigue-crack tip. The fracture toughness of in-situ composites is comparable to those of the toughest steels and crystalline Ti alloys. During steady-state crack-growth, the confinement of damage by in-situ dendrites results in enhancement of the toughness.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11172281)
文摘Dynamic strength behavior of Zr51Ti5NiloCu25A19 bulk metallic glass (BMG) up to 66 GPa was investigated in a series of plate impact shock-release and shock-reload experiments. Particle velocity profiles measured at the sample/LiF window interface were used to estimate the shear stress, shear modulus, and yield stress in shocked BMG. Beyond confirm- ing the previously reported strain-softening of shear stress during the shock loading process for BMGs, it is also shown that the softened Zr-BMG still has a high shear modulus and can support large yield stress when released or reloaded from the shocked state, and both the shear modulus and the yield stress appear as strain-hardening behaviors. The work provides a much clearer picture of the strength behavior of BMGs under shock loading, which is useful to comprehensively understand the plastic deformation mechanisms of BMGs.
基金Projects(50874045,51301194)supported by the National Natural Science Foundation of ChinaProject(2144057)supported by the Beijing Natural Science Foundation,China
文摘Room-temperature mechanical properties of Cu50Zr40Ti10-xNix(0≤x≤4,mole fraction,%) bulk metallic glasses (BMG) with aspect ratios in the range of 1:1-2.5:1 and loading rates in the range of1×10^-5-1×10^-2s^-1were systematically investigated by room-temperatureuniaxialcompression test.In the condition of an aspect ratio of 1:1, the superplasticity can be clearly observed for Cu50Zr40Ti10BMG when the loading rate is1×10^-4s^-1, while for Cu50Zr40Ti10-xNix(x=1-3, mole fraction, %) BMGs when the loading rate is1×10^-2s^-1. The plastic strain (εp), yielding strength (σy) and fracture strength (σf) of the studied Cu-based BMGs significantly depend on the aspect ratio and the loading rate. In addition, theσyof the studied Cu-based BMGs with an aspect ratio of 1:1 is close to the σfof those with the other aspect ratios when the loading rate is1×10^-2s^-1. The mechanism for the mechanical response to the loading rate and the aspect ratiowas also discussed.
文摘Dynamic response and damage evolution of Zr_(70)Cu_(13)Ni_(9.8)Al_(3.6)Nb_(3.4)Y_(0.2) bulk metallic glass(Zr-based BMG)under impact pressure ranging from 4.03 GPa to 27.22 GPa were studied.The Hugoniot Elastic Limit(HEL)and the spalling Strength(σ_(sp))were measured as 7.09 GPa and 2.28 GPa,and the curve of impact velocity(D)and particle velocity(u)were also obtained.Under the strain rate of~10^(5)s^(-1),local crystallization phenomenon was observed.As increasing the impact pressure,the failure mode of Zr-based BMG changed from spallation to fragmentation caused by the combination of spalling cracks and longitudinal cracks.Cone-cup structures were also observed in the internal spalling zone via nano-CT characterization.When increasing the impact pressure,the thickness of Zr-based BMG increased after impact and the remelting and cladding layers were also observed on the fracture surfaces.The fragments of the specimen were welded after impact due to the high temperature remelting,which causes plastic deformation of Zr-based BMG under shock loading.
文摘The dynamic mechanical behaviors of hollow Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metal glass (BMG) are investigated using a splitting Hopkinson pressure bar (SHPB) in this study. Upon dynamic compressive loading, the hollow specimen exhibit lower strength and poor ductility, caused by the higher stress concentration for the hollow one through FEM modeling. The different strain-rate responses for the hollow specimen are compared and explained. On the fracture surface of the hollow samples, there are highly dense vein patterns, many liquid drops and fishbone-like patterns.
基金the financial support of the National Natural Science Foundation of China(No.51101110)the Youth Science Foundation of Shanxi Province.China(No. 2012021018-1)+2 种基金the Research Project Supported by Shanxi Scholarship Council of China(No.2012-032)Technology Foundation for Selected Overseas Chinese Scholar Ministry of Human Resources and Social Security of Chinathe Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi
文摘The advanced fabrication of in-situ dendrite/metallic glass matrix (MGM) composites is reviewed. Herein, the semi- solid processing and Bridgman solidification are two methods, which can make the dendrites homogeneously dispersed within the metallic glass matrix. Upon quasi-static compressive loading at room temperature, almost all the in-situ composites exhibit improved plasticity, due to the effective block to the fast propagation of shear bands. Upon quasi-static tensile loading at room temperature, although the composites possess tensile ductility, the inhomogeneous deformation and associated softening dominates. High volume-fractioned dendrites and network structures make in-situ composites distinguishingly plastic upon dynamic compression. In-situ composite exhibits high tensile strength and softening (necking) in the supercooled liquid region, since the presence of high volume-fractioned dendrites lowers the rheology of the viscous glass matrix at high temperatures. At cryogenic temperatures, a distinguishingly-increased maximum strength is available; however, a ductile-to-brittle transition seems to be present by lowering the temperature. Besides, improved tension-tension fatigue limit of 473 MPa and four-point-bending fatigue limit of 567 MPa are gained for Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 MGM composites. High volume-fraction dendrites within the glass matrix induce increased effectiveness on the blunting and propagating resistance of the fatigue-crack tip. The fracture toughness of in-situ composites is comparable to those of the toughest steels and crystalline Ti alloys. During steady-state crack-growth, the confinement of damage by in-situ dendrites results in enhancement of the toughness.