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J Z Jiang - One of the best experts on this subject based on the ideXlab platform.
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effect of loading rate on creep behavior and shear transformation zone in amorphous alloy thin films and its correlation with Deformation Mode transition
Thin Solid Films, 2019Co-Authors: Q P Cao, X D Wang, D X Zhang, C. Wang, S.y. Liu, Libin Sun, J Z JiangAbstract:Abstract The effects of loading rate on creep behavior and shear transformation zone (STZ) in magnetron sputtered La-Co-Al and Zr-Cu-Ni-Al amorphous alloy thin films were characterized through instrumented nanoindentation with a spherical indenter. It was revealed that with an increase in loading rate, both thin films became harder with a narrower distribution of mechanical response, and exhibited more pronounced creep displacement with higher creep strain rate. Based on cooperative shear Model, both STZ volume and activation energy were calculated by measuring the strain rate sensitivity during creep, showing an increasing tendency with loading rate. However, the strain rate sensitivity was found to decrease with loading rate. Furthermore, structural heterogeneity density, estimated by analyzing the stressed volume at yielding, decreased with loading rate. Therefore, with increasing loading rate, the STZ event can only be activated at detectable structural heterogeneities with relatively larger volume, and the number of available fertile sites was decreased, resulting in postponed shear band formation and suppressed Deformation Mode transition.
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surface compressive and softening effect on Deformation Mode transition in ni nb metallic glassy thin films a molecular dynamics study
Journal of Applied Physics, 2018Co-Authors: Lianyi Chen, Q P Cao, Hao Zhang, X D Wang, D X Zhang, J Z JiangAbstract:Size-dependent Deformation Mode transition in metallic glasses (MGs) attracts a lot of interest due to potential application in micro-devices, but the underlying mechanisms are still unclear from the perspective of structure, e.g., how the chemical composition affects the Deformation Mode transition in a particular system is mysterious as well and needs to be addressed. Here, a series of NixNb100−x (x = 30, 50, 62, and 70 at. %) MG thin films has been studied by molecular dynamics simulations for better understanding the thickness-dependent tensile behaviors. The results show that the Deformation Mode transition from highly-localized to non-localized occurs as the film thickness (t) approaches the critical size, tc, which strongly correlates with the chemical composition, i.e., a Ni-rich specimen with higher modulus has smaller tc. It is revealed that the softening and compressive effect of surface layers with about 0.4 nm thickness in terms of Voronoi volume is the key factor for this transition regardless of composition. We illustrate the surface softening effect in various MG thin films by introducing a softening coefficient (Ψ) parameter reflecting the structural difference between the surface layer and the internal part. It is found that the higher the Ψ, the severer the surface softening effect, and the larger the tc in the Ni-depleted specimen, indicating the importance of Ψ as an indicator for the Deformation Mode transition.Size-dependent Deformation Mode transition in metallic glasses (MGs) attracts a lot of interest due to potential application in micro-devices, but the underlying mechanisms are still unclear from the perspective of structure, e.g., how the chemical composition affects the Deformation Mode transition in a particular system is mysterious as well and needs to be addressed. Here, a series of NixNb100−x (x = 30, 50, 62, and 70 at. %) MG thin films has been studied by molecular dynamics simulations for better understanding the thickness-dependent tensile behaviors. The results show that the Deformation Mode transition from highly-localized to non-localized occurs as the film thickness (t) approaches the critical size, tc, which strongly correlates with the chemical composition, i.e., a Ni-rich specimen with higher modulus has smaller tc. It is revealed that the softening and compressive effect of surface layers with about 0.4 nm thickness in terms of Voronoi volume is the key factor for this transition regardle...
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anomalous Deformation Mode transition in amorphous mg zn ca thin films
Scripta Materialia, 2018Co-Authors: Q P Cao, X D Wang, D X Zhang, S.y. Liu, Changyao Wang, H J Fecht, J Z JiangAbstract:Abstract Deformation Mode transition (DMT) from highly-localized to non-localized in amorphous alloy thin films (AATFs) was expected to depend on the homologous temperature. Here, DMT in Mg-Zn-Ca AATF with high homologous temperature but intrinsic brittleness was monitored during film/substrate co-bending, and its critical size for DMT is much low compared to other compositions. Intrinsically brittle nature of Mg-based AATF that facilitates the shear band to unstable crack transition may be responsible for unexpected low critical size despite of high homologous temperature.
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The influence of glass transition temperature on the critical size for Deformation Mode transition in metallic glassy films
Scripta Materialia, 2014Co-Authors: Q P Cao, X D Wang, D X Zhang, C. Wang, S.y. Liu, J Z JiangAbstract:The size effect on the bending Deformation behaviour of magnetron-sputtered La 57 Al 25 Co 18 , Cu 50 Zr 50 and Fe 70 Y 8 B 22 glassy films was investigated. The transition of the Deformation Mode from highly localized to non-localized occurs as the film thickness reduces below the critical value, which does not exhibit a distinct dependence on Poisson’s ratio. By combining the already-reported critical size for Deformation Mode transition in various metallic glasses, it is found that the critical size is primarily proportional to the homologous temperature.
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stress state dependent Deformation behavior in ni nb metallic glassy film
Acta Materialia, 2012Co-Authors: Q P Cao, X D Wang, D X Zhang, J Z JiangAbstract:Abstract The transition in Deformation Mode from highly localized to non-localized Deformation was investigated in Ni 60 Nb 40 glassy film by monitoring the reduction in thickness during film/substrate co-bending. It is revealed that in addition to the film thickness, the Mode of plastic Deformation depends on the stress state. With the reduction in thickness of thin film, tensile stress can efficiently suppress the change in Deformation Mode from highly localized to non-localized Deformation in comparison with compressive stress. A mechanism for the stress-state-dependent Deformation Mode change in glassy alloys is discussed on the basis of the pressure/stress effect of plastic Deformation and Griffith’s crack-propagation criterion. This study provides distinct evidence of the Deformation Mode change in metallic glassy film via the variation in stress state, and also sheds light on the Deformation mechanism of glassy alloys.
Koichi Tsuchiya - One of the best experts on this subject based on the ideXlab platform.
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Coupling effect of Deformation Mode and temperature on tensile properties in TWIP type Ti–Mo alloy
Materials Science and Engineering: A, 2019Co-Authors: Kai Yao, Xiaohua Min, Satoshi Emura, Koichi TsuchiyaAbstract:Abstract The coupling effect of Deformation Mode and Deformation temperature from 298 K to 673 K on tensile properties was systematically studied in a Ti–15Mo alloy with {332} twinning-induced plasticity (TWIP) effect and a comparison material of Ti–15Mo–1Fe alloy deformed by dislocation slip. The yield strength remained relatively constant in Ti–15Mo alloy, while it monotonously decreased in Ti–15Mo–1Fe alloy as increasing Deformation temperature. Due to enhancement of β phase stability from ω phase precipitation, the {332} twinning was suppressed and the contribution of dislocation slip to plastic Deformation increased, which compensated the thermal softening effect in Ti–15Mo alloy. High strain hardening rate was induced in Ti–15Mo alloy at 298 K due to the dynamic Hall-Petch effect from amounts of {332} twins and formation of abundant geometrically necessary dislocations (GNDs). As increasing Deformation temperature, the suppression of dynamic Hall-Petch effect and GNDs formation as well as the enhancement of dynamic recovery rate of dislocations resulted in the continuous decrease in strain hardening rate.
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effect of oxygen content on Deformation Mode and corrosion behavior in β type ti mo alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Xiaohua Min, Satoshi Emura, Pengfei Bai, Congqian Cheng, Beibei Jiang, Koichi TsuchiyaAbstract:Abstract This study examined microstructural characteristics and mechanical properties in a β-type Ti-15Mo alloy (mass%) with different oxygen contents, and their corrosion behavior in simulated physiological media. With increasing oxygen content from 0.1–0.5%, lattice parameter of parent β-phase increased from X-ray diffraction profiles, and spots of athermal ω-phase became weak and diffuse through transmission electron microscopy observations. {332} twin density decreased with an increase in oxygen content from 0.1–0.3% based on electron backscattered diffraction analyses, and it became almost zero when further increased oxygen content up to 0.5%. The solute oxygen atoms led to both a transition of {332} twinning to dislocation slip and a suppression of β-phase to ω-phase transformation. Room-temperature tensile testing of this alloy with oxygen content ranging from 0.1–0.5%, revealed that yield strength ranged from 420 MPa to 1180 MPa and that uniform elongation ranged from 47–0.2%. The oxygen-added alloys kept a low elastic modulus obtained from stress-strain curves, and exhibited good corrosion resistance in Ringer's solution from open-circuit potential and potentiodynamic polarization measurements. A desirable balance between mechanical properties and corrosion resistance is obtainable in this alloy as biomaterials through utilizing oxygen to control the Deformation Mode.
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reversible transition of Deformation Mode by structural rejuvenation and relaxation in bulk metallic glass
Applied Physics Letters, 2012Co-Authors: Fanqiang Meng, Koichi Tsuchiya, Yoshihiko YokoyamaAbstract:A transition of the Deformation Mode from heterogeneous, localized Deformation to homogeneous Deformation was observed in Zr50Cu40Al10 bulk metallic glass (BMG) by giant straining using the high-pressure torsion (HPT) method. The transition is accompanied by a pronounced decrease in hardness and elastic modulus as measured by nanoindentation. Annealing of the deformed BMG resulted in the restoration of the localized Deformation, hardness, and elastic modulus; thus, the transition is reversible. The observed reversible transition can be attributed to a change in the local atomic environment in the rejuvenated volume and the relaxed one.
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microstructure tensile Deformation Mode and crevice corrosion resistance in ti 10mo xfe alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Satoshi Emura, Koichi Tsuchiya, T Nishimura, Kaneaki TsuzakiAbstract:Abstract The microstructure, the tensile Deformation Mode at ambient temperature and the crevice corrosion resistance at a high temperature of 373 K were investigated in the Ti–10Mo–xFe (x = 0, 1, 3, 5) alloys. The stability of the β phase increased, and the formation of the α″ martensite and the athermal ω phase was suppressed by the increase in the Fe content. EPMA examinations indicated that the existence of the α″ martensite in the Ti–10Mo alloy was caused by the solidification segregation of Mo atoms. EBSD observations showed that the Deformation Mode changed from a {3 3 2}〈1 1 3〉 twinning to a slip by an increase in the Fe content, which coincided with the prediction by the electron/atom (e/a) ratio. The Ti–10Mo–3Fe alloy showed the highest yield strength of 935 MPa among all the alloys, while the Ti–10Mo–1Fe alloy showed the lowest value of 563 MPa due to the change in the Deformation Mode. On the other hand, all the alloys exhibited a high crevice corrosion resistance in a high chloride and high acidic solution at the high temperature, although the corrosion resistance decreased with an increase in the Fe content. The decrease in the corrosion resistance can be explained by the bond order (Bo). A good combination of tensile properties and crevice corrosion resistance may be obtainable through a further optimization of the Fe content by the e/a ratio and the Bo.
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effects of fe addition on tensile Deformation Mode and crevice corrosion resistance in ti 15mo alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Satoshi Emura, Koichi Tsuchiya, T Nishimura, Kaneaki Tsuzaki, Nobuaki SekidoAbstract:Abstract The tensile Deformation Mode at ambient temperature and the crevice corrosion resistance at a high temperature of 373 K were investigated in Ti–15Mo and Ti–15Mo–1Fe (mass%) alloys. The β phase stability increased, and the formation of an athermal ω phase was suppressed by the Fe addition. EBSD and TEM observations showed that the Deformation Mode in the Ti–15Mo alloy changed from a {3 3 2}〈1 1 3〉 twinning to a slip by the Fe addition, which coincided with the predictions from the electron/atom (e/a) ratio and the Mo equivalency. EPMA examinations indicated that the existence of twins in a few regions in the Ti–15Mo–1Fe alloy was caused by the solidification segregation of Mo and Fe atoms. The yield strength of the Ti–15Mo–1Fe alloy of 837 MPa was much higher than that of the Ti–15Mo alloy of 439 MPa due to the change in the Deformation Mode. The Ti–15Mo–1Fe alloy maintained an extremely high crevice corrosion resistance in a 10% NaCl water solution with a pH value of 0.5 at 373 K since there was no significant decrease in the average value of the bond order (Bo). A good combination of tensile properties, crevice corrosion resistance and cost is thought to be obtainable through further optimization of the chemical compositions by the e/a ratio, the Mo equivalency and the Bo.
Q P Cao - One of the best experts on this subject based on the ideXlab platform.
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effect of loading rate on creep behavior and shear transformation zone in amorphous alloy thin films and its correlation with Deformation Mode transition
Thin Solid Films, 2019Co-Authors: Q P Cao, X D Wang, D X Zhang, C. Wang, S.y. Liu, Libin Sun, J Z JiangAbstract:Abstract The effects of loading rate on creep behavior and shear transformation zone (STZ) in magnetron sputtered La-Co-Al and Zr-Cu-Ni-Al amorphous alloy thin films were characterized through instrumented nanoindentation with a spherical indenter. It was revealed that with an increase in loading rate, both thin films became harder with a narrower distribution of mechanical response, and exhibited more pronounced creep displacement with higher creep strain rate. Based on cooperative shear Model, both STZ volume and activation energy were calculated by measuring the strain rate sensitivity during creep, showing an increasing tendency with loading rate. However, the strain rate sensitivity was found to decrease with loading rate. Furthermore, structural heterogeneity density, estimated by analyzing the stressed volume at yielding, decreased with loading rate. Therefore, with increasing loading rate, the STZ event can only be activated at detectable structural heterogeneities with relatively larger volume, and the number of available fertile sites was decreased, resulting in postponed shear band formation and suppressed Deformation Mode transition.
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surface compressive and softening effect on Deformation Mode transition in ni nb metallic glassy thin films a molecular dynamics study
Journal of Applied Physics, 2018Co-Authors: Lianyi Chen, Q P Cao, Hao Zhang, X D Wang, D X Zhang, J Z JiangAbstract:Size-dependent Deformation Mode transition in metallic glasses (MGs) attracts a lot of interest due to potential application in micro-devices, but the underlying mechanisms are still unclear from the perspective of structure, e.g., how the chemical composition affects the Deformation Mode transition in a particular system is mysterious as well and needs to be addressed. Here, a series of NixNb100−x (x = 30, 50, 62, and 70 at. %) MG thin films has been studied by molecular dynamics simulations for better understanding the thickness-dependent tensile behaviors. The results show that the Deformation Mode transition from highly-localized to non-localized occurs as the film thickness (t) approaches the critical size, tc, which strongly correlates with the chemical composition, i.e., a Ni-rich specimen with higher modulus has smaller tc. It is revealed that the softening and compressive effect of surface layers with about 0.4 nm thickness in terms of Voronoi volume is the key factor for this transition regardless of composition. We illustrate the surface softening effect in various MG thin films by introducing a softening coefficient (Ψ) parameter reflecting the structural difference between the surface layer and the internal part. It is found that the higher the Ψ, the severer the surface softening effect, and the larger the tc in the Ni-depleted specimen, indicating the importance of Ψ as an indicator for the Deformation Mode transition.Size-dependent Deformation Mode transition in metallic glasses (MGs) attracts a lot of interest due to potential application in micro-devices, but the underlying mechanisms are still unclear from the perspective of structure, e.g., how the chemical composition affects the Deformation Mode transition in a particular system is mysterious as well and needs to be addressed. Here, a series of NixNb100−x (x = 30, 50, 62, and 70 at. %) MG thin films has been studied by molecular dynamics simulations for better understanding the thickness-dependent tensile behaviors. The results show that the Deformation Mode transition from highly-localized to non-localized occurs as the film thickness (t) approaches the critical size, tc, which strongly correlates with the chemical composition, i.e., a Ni-rich specimen with higher modulus has smaller tc. It is revealed that the softening and compressive effect of surface layers with about 0.4 nm thickness in terms of Voronoi volume is the key factor for this transition regardle...
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anomalous Deformation Mode transition in amorphous mg zn ca thin films
Scripta Materialia, 2018Co-Authors: Q P Cao, X D Wang, D X Zhang, S.y. Liu, Changyao Wang, H J Fecht, J Z JiangAbstract:Abstract Deformation Mode transition (DMT) from highly-localized to non-localized in amorphous alloy thin films (AATFs) was expected to depend on the homologous temperature. Here, DMT in Mg-Zn-Ca AATF with high homologous temperature but intrinsic brittleness was monitored during film/substrate co-bending, and its critical size for DMT is much low compared to other compositions. Intrinsically brittle nature of Mg-based AATF that facilitates the shear band to unstable crack transition may be responsible for unexpected low critical size despite of high homologous temperature.
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The influence of glass transition temperature on the critical size for Deformation Mode transition in metallic glassy films
Scripta Materialia, 2014Co-Authors: Q P Cao, X D Wang, D X Zhang, C. Wang, S.y. Liu, J Z JiangAbstract:The size effect on the bending Deformation behaviour of magnetron-sputtered La 57 Al 25 Co 18 , Cu 50 Zr 50 and Fe 70 Y 8 B 22 glassy films was investigated. The transition of the Deformation Mode from highly localized to non-localized occurs as the film thickness reduces below the critical value, which does not exhibit a distinct dependence on Poisson’s ratio. By combining the already-reported critical size for Deformation Mode transition in various metallic glasses, it is found that the critical size is primarily proportional to the homologous temperature.
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stress state dependent Deformation behavior in ni nb metallic glassy film
Acta Materialia, 2012Co-Authors: Q P Cao, X D Wang, D X Zhang, J Z JiangAbstract:Abstract The transition in Deformation Mode from highly localized to non-localized Deformation was investigated in Ni 60 Nb 40 glassy film by monitoring the reduction in thickness during film/substrate co-bending. It is revealed that in addition to the film thickness, the Mode of plastic Deformation depends on the stress state. With the reduction in thickness of thin film, tensile stress can efficiently suppress the change in Deformation Mode from highly localized to non-localized Deformation in comparison with compressive stress. A mechanism for the stress-state-dependent Deformation Mode change in glassy alloys is discussed on the basis of the pressure/stress effect of plastic Deformation and Griffith’s crack-propagation criterion. This study provides distinct evidence of the Deformation Mode change in metallic glassy film via the variation in stress state, and also sheds light on the Deformation mechanism of glassy alloys.
Kaneaki Tsuzaki - One of the best experts on this subject based on the ideXlab platform.
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effect of strain amplitude on the low cycle fatigue behavior of a new fe 15mn 10cr 8ni 4si seismic damping alloy
International Journal of Fatigue, 2016Co-Authors: Takahiro Sawaguchi, Kaneaki Tsuzaki, Ilya Nikulin, Atsumichi Kushibe, Yasuhiko Inoue, Hiroaki OtsukaAbstract:Abstract The low-cycle fatigue (LCF) properties and post-fatigue microstructure of a Fe–15Mn–10Cr–8Ni–4Si austenitic alloy were investigated under an axial strain control Mode with total strain amplitudes, Δet/2, ranging from 2.5 × 10−3 to 2 × 10−2. The fatigue resistance of the alloy was described by Coffin–Manson’s and Basquin’s relationships, and the corresponding fatigue parameters were evaluated. In addition, the Masing behavior, which is associated with a constant Deformation Mode during fatigue, was revealed at the examined strain amplitudes. Microstructural observations of the fatigue fractured samples showed that the strain induced e-martensitic transformation accompanied by a planar slip of the Shockley partial dislocations in the austenite is the main Deformation Mode controlling the fatigue behavior of the studied alloy at Δet/2
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microstructure tensile Deformation Mode and crevice corrosion resistance in ti 10mo xfe alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Satoshi Emura, Koichi Tsuchiya, T Nishimura, Kaneaki TsuzakiAbstract:Abstract The microstructure, the tensile Deformation Mode at ambient temperature and the crevice corrosion resistance at a high temperature of 373 K were investigated in the Ti–10Mo–xFe (x = 0, 1, 3, 5) alloys. The stability of the β phase increased, and the formation of the α″ martensite and the athermal ω phase was suppressed by the increase in the Fe content. EPMA examinations indicated that the existence of the α″ martensite in the Ti–10Mo alloy was caused by the solidification segregation of Mo atoms. EBSD observations showed that the Deformation Mode changed from a {3 3 2}〈1 1 3〉 twinning to a slip by an increase in the Fe content, which coincided with the prediction by the electron/atom (e/a) ratio. The Ti–10Mo–3Fe alloy showed the highest yield strength of 935 MPa among all the alloys, while the Ti–10Mo–1Fe alloy showed the lowest value of 563 MPa due to the change in the Deformation Mode. On the other hand, all the alloys exhibited a high crevice corrosion resistance in a high chloride and high acidic solution at the high temperature, although the corrosion resistance decreased with an increase in the Fe content. The decrease in the corrosion resistance can be explained by the bond order (Bo). A good combination of tensile properties and crevice corrosion resistance may be obtainable through a further optimization of the Fe content by the e/a ratio and the Bo.
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effects of fe addition on tensile Deformation Mode and crevice corrosion resistance in ti 15mo alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Satoshi Emura, Koichi Tsuchiya, T Nishimura, Kaneaki Tsuzaki, Nobuaki SekidoAbstract:Abstract The tensile Deformation Mode at ambient temperature and the crevice corrosion resistance at a high temperature of 373 K were investigated in Ti–15Mo and Ti–15Mo–1Fe (mass%) alloys. The β phase stability increased, and the formation of an athermal ω phase was suppressed by the Fe addition. EBSD and TEM observations showed that the Deformation Mode in the Ti–15Mo alloy changed from a {3 3 2}〈1 1 3〉 twinning to a slip by the Fe addition, which coincided with the predictions from the electron/atom (e/a) ratio and the Mo equivalency. EPMA examinations indicated that the existence of twins in a few regions in the Ti–15Mo–1Fe alloy was caused by the solidification segregation of Mo and Fe atoms. The yield strength of the Ti–15Mo–1Fe alloy of 837 MPa was much higher than that of the Ti–15Mo alloy of 439 MPa due to the change in the Deformation Mode. The Ti–15Mo–1Fe alloy maintained an extremely high crevice corrosion resistance in a 10% NaCl water solution with a pH value of 0.5 at 373 K since there was no significant decrease in the average value of the bond order (Bo). A good combination of tensile properties, crevice corrosion resistance and cost is thought to be obtainable through further optimization of the chemical compositions by the e/a ratio, the Mo equivalency and the Bo.
X D Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of loading rate on creep behavior and shear transformation zone in amorphous alloy thin films and its correlation with Deformation Mode transition
Thin Solid Films, 2019Co-Authors: Q P Cao, X D Wang, D X Zhang, C. Wang, S.y. Liu, Libin Sun, J Z JiangAbstract:Abstract The effects of loading rate on creep behavior and shear transformation zone (STZ) in magnetron sputtered La-Co-Al and Zr-Cu-Ni-Al amorphous alloy thin films were characterized through instrumented nanoindentation with a spherical indenter. It was revealed that with an increase in loading rate, both thin films became harder with a narrower distribution of mechanical response, and exhibited more pronounced creep displacement with higher creep strain rate. Based on cooperative shear Model, both STZ volume and activation energy were calculated by measuring the strain rate sensitivity during creep, showing an increasing tendency with loading rate. However, the strain rate sensitivity was found to decrease with loading rate. Furthermore, structural heterogeneity density, estimated by analyzing the stressed volume at yielding, decreased with loading rate. Therefore, with increasing loading rate, the STZ event can only be activated at detectable structural heterogeneities with relatively larger volume, and the number of available fertile sites was decreased, resulting in postponed shear band formation and suppressed Deformation Mode transition.
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surface compressive and softening effect on Deformation Mode transition in ni nb metallic glassy thin films a molecular dynamics study
Journal of Applied Physics, 2018Co-Authors: Lianyi Chen, Q P Cao, Hao Zhang, X D Wang, D X Zhang, J Z JiangAbstract:Size-dependent Deformation Mode transition in metallic glasses (MGs) attracts a lot of interest due to potential application in micro-devices, but the underlying mechanisms are still unclear from the perspective of structure, e.g., how the chemical composition affects the Deformation Mode transition in a particular system is mysterious as well and needs to be addressed. Here, a series of NixNb100−x (x = 30, 50, 62, and 70 at. %) MG thin films has been studied by molecular dynamics simulations for better understanding the thickness-dependent tensile behaviors. The results show that the Deformation Mode transition from highly-localized to non-localized occurs as the film thickness (t) approaches the critical size, tc, which strongly correlates with the chemical composition, i.e., a Ni-rich specimen with higher modulus has smaller tc. It is revealed that the softening and compressive effect of surface layers with about 0.4 nm thickness in terms of Voronoi volume is the key factor for this transition regardless of composition. We illustrate the surface softening effect in various MG thin films by introducing a softening coefficient (Ψ) parameter reflecting the structural difference between the surface layer and the internal part. It is found that the higher the Ψ, the severer the surface softening effect, and the larger the tc in the Ni-depleted specimen, indicating the importance of Ψ as an indicator for the Deformation Mode transition.Size-dependent Deformation Mode transition in metallic glasses (MGs) attracts a lot of interest due to potential application in micro-devices, but the underlying mechanisms are still unclear from the perspective of structure, e.g., how the chemical composition affects the Deformation Mode transition in a particular system is mysterious as well and needs to be addressed. Here, a series of NixNb100−x (x = 30, 50, 62, and 70 at. %) MG thin films has been studied by molecular dynamics simulations for better understanding the thickness-dependent tensile behaviors. The results show that the Deformation Mode transition from highly-localized to non-localized occurs as the film thickness (t) approaches the critical size, tc, which strongly correlates with the chemical composition, i.e., a Ni-rich specimen with higher modulus has smaller tc. It is revealed that the softening and compressive effect of surface layers with about 0.4 nm thickness in terms of Voronoi volume is the key factor for this transition regardle...
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anomalous Deformation Mode transition in amorphous mg zn ca thin films
Scripta Materialia, 2018Co-Authors: Q P Cao, X D Wang, D X Zhang, S.y. Liu, Changyao Wang, H J Fecht, J Z JiangAbstract:Abstract Deformation Mode transition (DMT) from highly-localized to non-localized in amorphous alloy thin films (AATFs) was expected to depend on the homologous temperature. Here, DMT in Mg-Zn-Ca AATF with high homologous temperature but intrinsic brittleness was monitored during film/substrate co-bending, and its critical size for DMT is much low compared to other compositions. Intrinsically brittle nature of Mg-based AATF that facilitates the shear band to unstable crack transition may be responsible for unexpected low critical size despite of high homologous temperature.
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The influence of glass transition temperature on the critical size for Deformation Mode transition in metallic glassy films
Scripta Materialia, 2014Co-Authors: Q P Cao, X D Wang, D X Zhang, C. Wang, S.y. Liu, J Z JiangAbstract:The size effect on the bending Deformation behaviour of magnetron-sputtered La 57 Al 25 Co 18 , Cu 50 Zr 50 and Fe 70 Y 8 B 22 glassy films was investigated. The transition of the Deformation Mode from highly localized to non-localized occurs as the film thickness reduces below the critical value, which does not exhibit a distinct dependence on Poisson’s ratio. By combining the already-reported critical size for Deformation Mode transition in various metallic glasses, it is found that the critical size is primarily proportional to the homologous temperature.
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stress state dependent Deformation behavior in ni nb metallic glassy film
Acta Materialia, 2012Co-Authors: Q P Cao, X D Wang, D X Zhang, J Z JiangAbstract:Abstract The transition in Deformation Mode from highly localized to non-localized Deformation was investigated in Ni 60 Nb 40 glassy film by monitoring the reduction in thickness during film/substrate co-bending. It is revealed that in addition to the film thickness, the Mode of plastic Deformation depends on the stress state. With the reduction in thickness of thin film, tensile stress can efficiently suppress the change in Deformation Mode from highly localized to non-localized Deformation in comparison with compressive stress. A mechanism for the stress-state-dependent Deformation Mode change in glassy alloys is discussed on the basis of the pressure/stress effect of plastic Deformation and Griffith’s crack-propagation criterion. This study provides distinct evidence of the Deformation Mode change in metallic glassy film via the variation in stress state, and also sheds light on the Deformation mechanism of glassy alloys.