Acoustic emission(AE)of 316 L stainless steel with of low Ni content shows,under tension,simultaneously three avalanche processes.One avalanche process relates to the movement of dislocations,the others to martensitic...Acoustic emission(AE)of 316 L stainless steel with of low Ni content shows,under tension,simultaneously three avalanche processes.One avalanche process relates to the movement of dislocations,the others to martensitic transformations and detwinning/twinning.Detwinning/twinning occurs predominantly at the early stage of the plastic deformation while martensitic transformations only become observable after large plastic deformation.All processes coincide during deformation with variable effect on AE.An excellent fingerprint for the detection of the coincidence between the several mechanisms is the observation of multivalued E~A^(2) correlations.AE signals from moving dislocations decay more slowly(~7×10^(-3)s)and show long avalanche durations.In contrast,AE signals during martensitic transformations and detwinning/twinning decay rapidly(<4×10^(-4) s)and show short avalanche durations.They can be distinguished by different energy exponents of their avalanches.The energy distributions of the mechanisms differ because energies are defined as the integral over the squared AE amplitudes,where the integration extends over the avalanche durations.A combination of statistical analysis with Convolutional Neural Network calculations provides an accurate and straightforward method for online,non-destructive avalanche monitoring of strain-induced martensitic transformations in 316 L steel under high strain.展开更多
Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,her...Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,here we investigated the hydrogen-defect interaction by comparing the dislocation structure evolution after hydrogen adsorption and desorption in a Fe-28Mn-0.3C(wt%)twinning-induced plasticity steel with an austenitic structure using in situ electron channeling contrast imaging.The results indicate that hydrogen can strongly affect dislocation activities.In detail,hydrogen can promote the formation of stacking faults with a long dissociation distance.Besides,dislocation movements are frequently observed during hydrogen desorption.The required resolved shear stress is considered to be the residual stresses rendered by hydrogen segregation.Furthermore,the microstructural heterogeneity could lead to the discrepancy of dislocation activities even within the same materials.展开更多
High- and medium-Mn (H/M-Mn) base lightweight steels are a class of ultrastrong structural materials with high ductility compared to their low-Mn counterparts with low strength and poor ductility.However, producing th...High- and medium-Mn (H/M-Mn) base lightweight steels are a class of ultrastrong structural materials with high ductility compared to their low-Mn counterparts with low strength and poor ductility.However, producing these H/M-Mn materials requires the advanced or high-tech manufacturing techniques, which can unavoidably provoke labor and cost concerns. Herein, we have developed a facilestrategy that circumvents the strength–ductility trade-off in low-Mn ferritic lightweight steels, by employing low-temperature tempering-induced partitioning (LTP). This LTP treatment affords a typical Fe-2.8Mn-5.7Al-0.3C (wt.%) steel with a heterogeneous size-distribution of metastable austenite embeddedin a ferrite matrix for partitioning more carbon into smaller austenite grains than into the larger austenite ones. This size-dependent partitioning results in slip plane spacing modification and lattice strain,which act through dislocation engineering. We ascribe the simultaneous improvement in strength andtotal elongation to both the size-dependent dislocation movement in austenite grains and the controlleddeformation-induced martensitic transformation. The low-carbon-partitioned large austenite grains increase the strength and ductility as a consequence of the combined martensitic transformation andhigh dislocation density-induced hardening and by interface strengthening. Additionally, high-carbonpartitioned small austenite grains enhance the strength and ductility by planar dislocation glide (inthe low strain regime) and by cross-slipping and delayed martensitic transformation (in the high strainregime). The concept of size-dependent dislocation engineering may provide different pathways for developing a wide range of heterogeneous-structured low-Mn lightweight steels, suggesting that LTP maybe desirable for broad industrial applications at an economic cost.展开更多
Inorganic semiconductors are widely used in many fields such as information,energy,and electronics due to their rich functionalities.The chemical bonds in inorganic semiconductors are usually directional covalent bond...Inorganic semiconductors are widely used in many fields such as information,energy,and electronics due to their rich functionalities.The chemical bonds in inorganic semiconductors are usually directional covalent bonds,which inhibit the movement of dislocations.Thus,being different with metals and alloys,inorganic semiconductors are usually brittle at room temperature,with very small strain below 1%and poor machinability[1].Many metalworking techniques,such as the cold-forming processing,which is a crucial means for the cost-effective production of metal and alloy parts,cannot be applied to most inorganic semiconductors,greatly limiting their low-cost fabrication and applications in flexible electronics.展开更多
1.Introduction The strength of metallic materials can be ameliorated by introducing boundaries,precipitates,or defects as obstacles to dislocation movement[1].However,high strength is generally obtained at the sacrifi...1.Introduction The strength of metallic materials can be ameliorated by introducing boundaries,precipitates,or defects as obstacles to dislocation movement[1].However,high strength is generally obtained at the sacrifice of plastic deformation capability[2].Lately,many strategies have been proposed to improve the comprehensive properties of materials,among which manipulating stacking fault energy(SFE)is effective[3–5].展开更多
基金Financial support from the National Natural Science Foundation of China(51931004)111 project 2.0(BP2018008)+1 种基金EKHS thanks EPSRC(EP/P024904/1)the EU(Horizon 2020 programme under the Marie Sk?odowska-Curie grant agreement No 861153)for support。
文摘Acoustic emission(AE)of 316 L stainless steel with of low Ni content shows,under tension,simultaneously three avalanche processes.One avalanche process relates to the movement of dislocations,the others to martensitic transformations and detwinning/twinning.Detwinning/twinning occurs predominantly at the early stage of the plastic deformation while martensitic transformations only become observable after large plastic deformation.All processes coincide during deformation with variable effect on AE.An excellent fingerprint for the detection of the coincidence between the several mechanisms is the observation of multivalued E~A^(2) correlations.AE signals from moving dislocations decay more slowly(~7×10^(-3)s)and show long avalanche durations.In contrast,AE signals during martensitic transformations and detwinning/twinning decay rapidly(<4×10^(-4) s)and show short avalanche durations.They can be distinguished by different energy exponents of their avalanches.The energy distributions of the mechanisms differ because energies are defined as the integral over the squared AE amplitudes,where the integration extends over the avalanche durations.A combination of statistical analysis with Convolutional Neural Network calculations provides an accurate and straightforward method for online,non-destructive avalanche monitoring of strain-induced martensitic transformations in 316 L steel under high strain.
基金This work was financially supported by the National Natural Science Foundation of China(No.52101022)the Shaanxi Province Natural Science Foundation(No.2021JQ-080).
文摘Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,here we investigated the hydrogen-defect interaction by comparing the dislocation structure evolution after hydrogen adsorption and desorption in a Fe-28Mn-0.3C(wt%)twinning-induced plasticity steel with an austenitic structure using in situ electron channeling contrast imaging.The results indicate that hydrogen can strongly affect dislocation activities.In detail,hydrogen can promote the formation of stacking faults with a long dissociation distance.Besides,dislocation movements are frequently observed during hydrogen desorption.The required resolved shear stress is considered to be the residual stresses rendered by hydrogen segregation.Furthermore,the microstructural heterogeneity could lead to the discrepancy of dislocation activities even within the same materials.
基金The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.Patent application(Korean Patent application number 10-2020-0172118)has been filed based on the results of this study。
文摘High- and medium-Mn (H/M-Mn) base lightweight steels are a class of ultrastrong structural materials with high ductility compared to their low-Mn counterparts with low strength and poor ductility.However, producing these H/M-Mn materials requires the advanced or high-tech manufacturing techniques, which can unavoidably provoke labor and cost concerns. Herein, we have developed a facilestrategy that circumvents the strength–ductility trade-off in low-Mn ferritic lightweight steels, by employing low-temperature tempering-induced partitioning (LTP). This LTP treatment affords a typical Fe-2.8Mn-5.7Al-0.3C (wt.%) steel with a heterogeneous size-distribution of metastable austenite embeddedin a ferrite matrix for partitioning more carbon into smaller austenite grains than into the larger austenite ones. This size-dependent partitioning results in slip plane spacing modification and lattice strain,which act through dislocation engineering. We ascribe the simultaneous improvement in strength andtotal elongation to both the size-dependent dislocation movement in austenite grains and the controlleddeformation-induced martensitic transformation. The low-carbon-partitioned large austenite grains increase the strength and ductility as a consequence of the combined martensitic transformation andhigh dislocation density-induced hardening and by interface strengthening. Additionally, high-carbonpartitioned small austenite grains enhance the strength and ductility by planar dislocation glide (inthe low strain regime) and by cross-slipping and delayed martensitic transformation (in the high strainregime). The concept of size-dependent dislocation engineering may provide different pathways for developing a wide range of heterogeneous-structured low-Mn lightweight steels, suggesting that LTP maybe desirable for broad industrial applications at an economic cost.
文摘Inorganic semiconductors are widely used in many fields such as information,energy,and electronics due to their rich functionalities.The chemical bonds in inorganic semiconductors are usually directional covalent bonds,which inhibit the movement of dislocations.Thus,being different with metals and alloys,inorganic semiconductors are usually brittle at room temperature,with very small strain below 1%and poor machinability[1].Many metalworking techniques,such as the cold-forming processing,which is a crucial means for the cost-effective production of metal and alloy parts,cannot be applied to most inorganic semiconductors,greatly limiting their low-cost fabrication and applications in flexible electronics.
基金financially supported by the National Natural Science Foundation of China(NSFC)under grant No.52371100.
文摘1.Introduction The strength of metallic materials can be ameliorated by introducing boundaries,precipitates,or defects as obstacles to dislocation movement[1].However,high strength is generally obtained at the sacrifice of plastic deformation capability[2].Lately,many strategies have been proposed to improve the comprehensive properties of materials,among which manipulating stacking fault energy(SFE)is effective[3–5].
