The mechanical properties and microstructure of two low carbon high manganese steels with 23.8% （No. 1） and 33% （No. 2） （mass percent） of manganese were investigated. The results showed that No. 1 steel possesse...The mechanical properties and microstructure of two low carbon high manganese steels with 23.8% （No. 1） and 33% （No. 2） （mass percent） of manganese were investigated. The results showed that No. 1 steel possesses high strength and high plasticity, and No. 2 steel has a relatively high strength and extraordinary plasticity. The No. 1 steel exhibits both TRIP （transformation induced plasticity） and TWIP （twin induced plasticity） effects during the deformation; while only TWIP effect appeared under the same deformation condition for No. 2 steel. The comparison between the microstructures and mechanical properties of two steels was made, and the strengthening mechanisms were also analyzed.展开更多
In this paper new high-strength and high-plasticity twinning induced plasticity （TWlP） steel for modern automobile body was investigated. Some basic experimental results were given. The results indicate the TWlP ste...In this paper new high-strength and high-plasticity twinning induced plasticity （TWlP） steel for modern automobile body was investigated. Some basic experimental results were given. The results indicate the TWlP steel has excellent properties. It exhibits high ultimate tensile strength （600,--1100 MPa） and extremely large elongation of 60% to 90%.In the future it would be capable of satisfying the requirements of new generation of vehicle.展开更多
The mechanical properties of the TWIP steel subjected to impact loading at various strain rates were analyzed by the split Hopkinson pressure bar. Meanwhile the microstructure of the TWIP steel fore-and-aft dynamic de...The mechanical properties of the TWIP steel subjected to impact loading at various strain rates were analyzed by the split Hopkinson pressure bar. Meanwhile the microstructure of the TWIP steel fore-and-aft dynamic deformation was oberseved and analyzed by optical microscope （OM）, X-ray diffraction （XRD）, and transmission electron microscope （TEM）. The results show that when the TWIP steel was deformed under dynamic condition, the stress, microhardness and work hardening rate increase with the increase of strain and strain rate; there is decline of work hardening rate for adiabatic temperature rising softening. There are many pin-like deformation twins in the microstructure of the TWIP steel subjected to impact loading, and the grain size after deformation is bigger than that before; the interaction of twins with dislocation and twins with twins, especially emergence of multiple deformation twins are the main strengthening mechanisms of the TWIP steel. The nucleation mechanism of deformation twins will be ＂rebound mechanism＂;the incomplete deformation twins can be observed when the strain rate is low; when strain rate increases, deformation twins unite together;and deformation twins become denser because the nucleation rate increases with increasing the strain rate.展开更多
Microstructures and mechanical properties of the 25Mn twinning induced plasticity （TWIP） steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 100...Microstructures and mechanical properties of the 25Mn twinning induced plasticity （TWIP） steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 1000℃, the 25Mn steel showed excellent comprehensive mechanical properties, the tensile strength was about 640 MPa, the yield strength was higher than 255 MPa, and the elongation was above 82%. The microstructure was analyzed by optical microscopy （OM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. Before deformation the microstructure was composed of austenitic matrix and annealing twins at room temperature; at the same time, a significant amount of annealing twins and stacking faults were observed by TEM. Mechanical twins played a dominant role in deformation and as a result the mechanical properties were found to be excellent.展开更多
High manganese twinning-induced plasticity （TWIP） steel is a new kind of structural material and possesses both high strength and superior plasticity and can meet the weight-lightening requirement for manufacturing ...High manganese twinning-induced plasticity （TWIP） steel is a new kind of structural material and possesses both high strength and superior plasticity and can meet the weight-lightening requirement for manufacturing vehicle body. The excellent formability of the TWIP steel comes from the extraordinary strain hardening effect during plastic deformation. The reduction of specific weight by aluminum alloying and strain hardening effect can lead to an effective weight reduction of the steel components, and provide a better choice for materials in vehicle body design. The TWIP effect in high Mn steels is generally associated with the successive work- hardening generated by twins and influenced by some factors, such as Mn content, AI addition revealed by stacking fault energy （SFE）, grain size, deformation temperature and strain rate. The present review introduces some aspects of the TWIP steels relating to their physical metallurgy, influencing factors associated with their deformation mechanisms, and a prospect for the future investigation is also described. Moreover, as a potential candidate for replacing Ni-Cr austenitic stainless steel, researches on the oxidation behavior and corrosion resistance of Fe-Mn-AI-C system steels are also reviewed.展开更多
By using scanning electron microscopy（SEM） equipped with electron back-scattered diffraction（EBSD）system, transmission electron microscopy（TEM） and Corr Test4 electrochemical workstation, effects of chromium con...By using scanning electron microscopy（SEM） equipped with electron back-scattered diffraction（EBSD）system, transmission electron microscopy（TEM） and Corr Test4 electrochemical workstation, effects of chromium content（1.35 wt% - 3.95 wt%） on the mechanical properties and anti-corrosion behaviours of high manganese Fe-Mn-C-Al-Cr-N twinning-induced plasticity（TWIP） steels were studied. The results show that Cr content has an obvious influence on the mechanical properties and fracture behaviors of the high manganese TWIP steels. The yield and ultimate tensile strengths of the steel sheets were improved with increasing Cr content while the elongation was reduced. In addition, with the increase of Cr content, the fracture mode changed from ductile fracture pattern with coarse dimples and tear ridges（Cr content ≤ 2.35%） to intergranular fracture（when Cr content is 3.95%）. Furthermore, Cr content has a tremendous effect on anti-corrosion behaviors of the high manganese TWIP steels. The increase of Cr content enhanced the corrosion resistance of the annealed steel sheets by improving the proportion of low-angle boundary.展开更多
As a new type of high manganese steel, the twinning induced plasticity （TWIP） steels have attracted a growing interest in the automotive industry due to their good performance. Thin plates of TWIP steel were welded ...As a new type of high manganese steel, the twinning induced plasticity （TWIP） steels have attracted a growing interest in the automotive industry due to their good performance. Thin plates of TWIP steel were welded by laser beam welding （LBW） and gas tungsten arc welding （GTAW）. The microstructure result shows that GTAW joint has obvious heat-affected zone （HAZ）, while the HAZ of LBW joint is almost invisible. The X-ray diffraction result shows that the phase compositions of both joints are austenitic and no phase transition occurs. Energy disper- sive spectrometry result shows that there is violent evaporation of Mn element in LBW joint, while the proportion of Mn element in GTAW joint is almost unchanged. Tensile tests and micro-hardness measurements were performed to take into account the mechanical properties of joints manufactured by the two different processes. The micro-hard- ness profiles of both joints present a typical saddle distribution, and the hardness of GTAW seam is lower than that of LBW seam. The failure positions of LBW joints are all located in base metal while the GTAW joints are all at the weld toe due to the softening of HAZ. By means of scanning electron microscopy, a typical ductile fracture is observed in LBW joint, while a brittle fracture with quasi-cleavage fracture characteristic is observed in GTAW joint.展开更多
The influence of cold rolling reduction on microstructure and mechanical properties of the TWIP （ttwinning induced plasticity） steel was investigated. The results＇ indicated that the steel had better comprehensive ...The influence of cold rolling reduction on microstructure and mechanical properties of the TWIP （ttwinning induced plasticity） steel was investigated. The results＇ indicated that the steel had better comprehensive mechanical properties when cold rolling reduction was about 65.0% and the annealing temperature was 1000℃. The tensile strength of the steel is about 640MPa and the yield strength is higher than 255MPa, while the elongation is＇ above 82%. The microstructure is composed of austenitic matrix and annealing twins at room temperature, at the same time, a significant amount of annealing twins and stacking faults＇ are observed by transmission electron microscopy （TEM）. Mechanical twins play a dominant role during deformation, and result in exceUent mechanical properties.展开更多
The aim of the present work was to study the effect of austenite grain size （AGS） on the martensite formation in a high-manganese twinning-induced plasticity （TWIP） steel. The results of a quantitative microstruct...The aim of the present work was to study the effect of austenite grain size （AGS） on the martensite formation in a high-manganese twinning-induced plasticity （TWIP） steel. The results of a quantitative microstructural characterization of the steel by the whole X-ray pattern fitting Rietveld software, materials analysis using diffraction （MAUD）, indicated that the volume fraction of αbcc-martensite increases with increasing AGS. However, the value of the stacking fault probability （Psf） does not show a large variation for samples with different values of AGS under water-quenching conditions.展开更多
The dynamic mechanical properties of Fe-30Mn-3Si-4A1 twinning induced plasticity （TWIP） steel were studied by the split-Hopkinson pressure bar （SHPB） at temperatures of 298-1073 K and strain rates of 700, 2500, an...The dynamic mechanical properties of Fe-30Mn-3Si-4A1 twinning induced plasticity （TWIP） steel were studied by the split-Hopkinson pressure bar （SHPB） at temperatures of 298-1073 K and strain rates of 700, 2500, and 5000 s-1. The TWIP steel indicates strain rate hardening effect between 700 and 2500 s-1, but it shows strain rate softening effect between 2500 and 5000 s-1. In addition, the strain rate softening effect enhances with an increase in deformation temperature. After deformation, the microstructures were studied by optical microscopy （OM）. It is shown that the deformation bands become more convergence, a part of which become interwoven with an increase in strain rate, and the dynamic recovery and recrystallization are enhanced with an increase in both temperature and strain rate.展开更多
Mechanical properties and microstructural evolution of the hot-rolled Fe-Mn-C-Si TWIP steel were investigated and the deformation mechanism was analyzed.The results showed that the tensile strength and elongation were...Mechanical properties and microstructural evolution of the hot-rolled Fe-Mn-C-Si TWIP steel were investigated and the deformation mechanism was analyzed.The results showed that the tensile strength and elongation were about 1050 MPa and 60%,respectively.The hot-rolled steel had high specific energy absorption and impact toughness between-120 ℃ and 20 ℃.Some inhomogeneous dislocation zones were observed in the undeformed steel.Lots of deformation twins and twin-dislocation interactions were observed in the deformed steel.TWIP effect was the major deformation mechanism for the excellent mechanical properties.展开更多
The fatigue performance and fracture mechanism of laser welded twinning induced plasticity（TWIP）steel joint were investigated experimentally based on the evolution of microstructure and micromechanical properties.Th...The fatigue performance and fracture mechanism of laser welded twinning induced plasticity（TWIP）steel joint were investigated experimentally based on the evolution of microstructure and micromechanical properties.The optical microscopy was used to analyze the evolution of microstructure.The variation of composition and phase structure of fusion zone were detected by energy dispersive X-ray and X-ray diffraction spectrometers.The micromechanical behaviors of the various zones were characterized using nanoindentation.The static tensile test and high cycle fatigue test were performed to evaluate the mechanical properties of welded joint and base metal.The microstructures,tensile properties and fatigue strength of base metal as well as welded metal were analyzed.The fatigue fracture surfaces of base metal and welded joint were observed by means of scanning electron microscopy,in order to identify fatigue crack initiation sites and propagation mechanisms.Moreover,the fatigue fracture characteristics and mechanisms for the laser welded TWIP steel joints were analyzed.展开更多
The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinninginduced plasticity(TWIP)steel processed using warm forging was investigated.It is found that steel processed via warm forging improve...The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinninginduced plasticity(TWIP)steel processed using warm forging was investigated.It is found that steel processed via warm forging improves comprehensive mechanical properties compared to the TWIP steel processed via cold rolling,with a high tensile strength(R_(m))of 793 MPa,a yield strength(R_(P))of 682 MPa,an extremely large R_(P)/R_(m)ratio as high as 0.86 as well as an excellent elongation rate of 46.8%.The microstructure observation demonstrates that steel processed by warm forging consists of large and elongated grains together with fine,equiaxed grains.Complicated micro-defect configurations were also observed within the steel,including dense dislocation networks and a few coarse deformation twins.As the plastic deformation proceeds,the densities of dislocations and deformation twins significantly increase.Moreover,a great number of slip lines could be observed in the elongated grains.These findings reveal that a much more dramatic interaction between microstructural defect and dislocations glide takes place in the forging sample,wherein the fine and equiaxed grains propagated dislocations more rapidly,together with initial defect configurations,are responsible for enhanced strength properties.Meanwhile,larger,elongated grains with more prevalently activated deformation twins result in high plasticity.展开更多
Graphene(Gr)reinforced high-entropy alloy(HEA)matrix composites are expected as potential candidates for next-generation structural applications in light of outstanding mechanical properties.A deep comprehension of th...Graphene(Gr)reinforced high-entropy alloy(HEA)matrix composites are expected as potential candidates for next-generation structural applications in light of outstanding mechanical properties.A deep comprehension of the underlying deformation mechanisms under extreme shock loading is of paramount importance,however,remains lacking due to experimentally technical limitations in existence.In the present study,by means of nonequilibrium molecular dynamics simulations,dynamic deformation behaviors and corresponding mechanisms in equiatomic FeNiCrCoCu HEA/Gr composite systems were investigated in terms of various shock velocities.The resistance to dislocation propagation imparted by Gr was corroborated to encourage the elevated local stress level by increasing the likelihood of dislocation interplays,which facilitated the onset of twins and hexagonal close-packed(HCP)martensite laths.Meanwhile,the advent of Gr was demonstrated to endow the HEA with an additional twinning pathway that induced a structural conversion from HCP to parent face-centered cubic(FCC)inside HCP martensite laths,different from the classical one that necessitated undergoing the intermediate procedure of extrinsic stacking fault(ESF)evolution.More than that,by virtue of an increase in flow stress,the transformation-induced plasticity(TRIP)effect was validated to be additionally evoked as the predominant strain accommodation mechanism at higher strains on the one hand,but which only assisted plasticity in pure systems,and on the other hand,can also act as an auxiliary regulation mode together with the twinning-induced plasticity(TWIP)effect under intermediate strains,but with enhanced contributions relative to pure systems.One may expect that TRIP and TWIP effects promoted by introducing Gr would considerably inspire a synergistic effect between strength and ductility,contributing to the exceptional shock-resistant performance of FeNiCrCoCu HEAs under extreme regimes.展开更多
As twinning-induced plasticity （TWIP） steel is one potential material for shaped charge liner due to the combination of high strength and high plasticity, deformation mechanism at high strain rate and high temperatu...As twinning-induced plasticity （TWIP） steel is one potential material for shaped charge liner due to the combination of high strength and high plasticity, deformation mechanism at high strain rate and high temperature is required to study. Compression experiments of Fe 30Mn-3Si-4Al TWIP steel were conducted using a Gleeble 1500 thermal simulation machine and a split-Hopkinson pressure bar （SHPB） between 298 and 1073 K at strain rates of 10 3 and 700 s-1 , respectively. Microstructures were observed using optical microscopy （OM） and transmission e- lectron microscopy （TEM）. Results show that flow stress and densities of deformation twins and dislocations de crease with increasing deformation temperature at strain rates of 10 3 and 700 s -1. The stack fault energy （SFE） values （Г） of Fe-30Mn-3Si-4Al TWIP steel at different temperatures were calculated using thermodynamic data. Based on corresponding microstructures, it can he inferred that at 700 s -1 , twinning is the main deformation mecha- nism at 298-573 K for 30 mJ/m2≤Г≤63 mJ/m2 , while dislocation gliding is the main deformation mechanism above 1 073 K for Г≥145 mJ/m2. In addition, with increasing strain rate from 10-3 to 700 s -1 , the SFE range of twinning is enlarged and the SEF value of twinning becomes higher.展开更多
The microstructure and crack behaviour of twinning induced plasticity （TWIP） steel during tensile deformation was investigated with in-situ scanning electron microscopy （SEM）. The results show that there are two m...The microstructure and crack behaviour of twinning induced plasticity （TWIP） steel during tensile deformation was investigated with in-situ scanning electron microscopy （SEM）. The results show that there are two modes of plastic deformation during tensile test in the Fe-Mn-C TWIP steel： dislocation gliding and deformation twins. During the process of tensile deformation, secondary deformed twins are found. Inclusions have played a role in the course of ductile fracture, and microcracks initiate from inclusions and twin-twin intersections.展开更多
文摘The mechanical properties and microstructure of two low carbon high manganese steels with 23.8% （No. 1） and 33% （No. 2） （mass percent） of manganese were investigated. The results showed that No. 1 steel possesses high strength and high plasticity, and No. 2 steel has a relatively high strength and extraordinary plasticity. The No. 1 steel exhibits both TRIP （transformation induced plasticity） and TWIP （twin induced plasticity） effects during the deformation; while only TWIP effect appeared under the same deformation condition for No. 2 steel. The comparison between the microstructures and mechanical properties of two steels was made, and the strengthening mechanisms were also analyzed.
文摘In this paper new high-strength and high-plasticity twinning induced plasticity （TWlP） steel for modern automobile body was investigated. Some basic experimental results were given. The results indicate the TWlP steel has excellent properties. It exhibits high ultimate tensile strength （600,--1100 MPa） and extremely large elongation of 60% to 90%.In the future it would be capable of satisfying the requirements of new generation of vehicle.
基金Item Sponsored by Scientific Research Plan of Shanxi Province of China(20090321072)
文摘The mechanical properties of the TWIP steel subjected to impact loading at various strain rates were analyzed by the split Hopkinson pressure bar. Meanwhile the microstructure of the TWIP steel fore-and-aft dynamic deformation was oberseved and analyzed by optical microscope （OM）, X-ray diffraction （XRD）, and transmission electron microscope （TEM）. The results show that when the TWIP steel was deformed under dynamic condition, the stress, microhardness and work hardening rate increase with the increase of strain and strain rate; there is decline of work hardening rate for adiabatic temperature rising softening. There are many pin-like deformation twins in the microstructure of the TWIP steel subjected to impact loading, and the grain size after deformation is bigger than that before; the interaction of twins with dislocation and twins with twins, especially emergence of multiple deformation twins are the main strengthening mechanisms of the TWIP steel. The nucleation mechanism of deformation twins will be ＂rebound mechanism＂;the incomplete deformation twins can be observed when the strain rate is low; when strain rate increases, deformation twins unite together;and deformation twins become denser because the nucleation rate increases with increasing the strain rate.
基金the National Natural Science Foundation of China (No.50575022)the Specialized Research Foundation for the Doctoral Program of Higher Education of China (No.20040008024)the National High-Tech Research and Development Program of China (No.2008AA03E502)
文摘Microstructures and mechanical properties of the 25Mn twinning induced plasticity （TWIP） steel at different annealing temperatures were investigated. The results indicated that when the annealing temperature was 1000℃, the 25Mn steel showed excellent comprehensive mechanical properties, the tensile strength was about 640 MPa, the yield strength was higher than 255 MPa, and the elongation was above 82%. The microstructure was analyzed by optical microscopy （OM）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. Before deformation the microstructure was composed of austenitic matrix and annealing twins at room temperature; at the same time, a significant amount of annealing twins and stacking faults were observed by TEM. Mechanical twins played a dominant role in deformation and as a result the mechanical properties were found to be excellent.
基金supported by the Fundamental Research Funds for the Central Universities (No. N100507003)
文摘High manganese twinning-induced plasticity （TWIP） steel is a new kind of structural material and possesses both high strength and superior plasticity and can meet the weight-lightening requirement for manufacturing vehicle body. The excellent formability of the TWIP steel comes from the extraordinary strain hardening effect during plastic deformation. The reduction of specific weight by aluminum alloying and strain hardening effect can lead to an effective weight reduction of the steel components, and provide a better choice for materials in vehicle body design. The TWIP effect in high Mn steels is generally associated with the successive work- hardening generated by twins and influenced by some factors, such as Mn content, AI addition revealed by stacking fault energy （SFE）, grain size, deformation temperature and strain rate. The present review introduces some aspects of the TWIP steels relating to their physical metallurgy, influencing factors associated with their deformation mechanisms, and a prospect for the future investigation is also described. Moreover, as a potential candidate for replacing Ni-Cr austenitic stainless steel, researches on the oxidation behavior and corrosion resistance of Fe-Mn-AI-C system steels are also reviewed.
基金financially supported by the Research Fund from Department of Education,Liaoning Province,China(Grant No.L20150168)the Fundamental Research Fund for Central Universities(No.N140203001)
文摘By using scanning electron microscopy（SEM） equipped with electron back-scattered diffraction（EBSD）system, transmission electron microscopy（TEM） and Corr Test4 electrochemical workstation, effects of chromium content（1.35 wt% - 3.95 wt%） on the mechanical properties and anti-corrosion behaviours of high manganese Fe-Mn-C-Al-Cr-N twinning-induced plasticity（TWIP） steels were studied. The results show that Cr content has an obvious influence on the mechanical properties and fracture behaviors of the high manganese TWIP steels. The yield and ultimate tensile strengths of the steel sheets were improved with increasing Cr content while the elongation was reduced. In addition, with the increase of Cr content, the fracture mode changed from ductile fracture pattern with coarse dimples and tear ridges（Cr content ≤ 2.35%） to intergranular fracture（when Cr content is 3.95%）. Furthermore, Cr content has a tremendous effect on anti-corrosion behaviors of the high manganese TWIP steels. The increase of Cr content enhanced the corrosion resistance of the annealed steel sheets by improving the proportion of low-angle boundary.
基金Item Sponsored by National Natural Science Foundation of China(51374151,51208333)Science and Technology Major Project of Shanxi Province of China(20111101053)Natural Science Foundation of Shanxi Province of China(2011011020-2)
文摘As a new type of high manganese steel, the twinning induced plasticity （TWIP） steels have attracted a growing interest in the automotive industry due to their good performance. Thin plates of TWIP steel were welded by laser beam welding （LBW） and gas tungsten arc welding （GTAW）. The microstructure result shows that GTAW joint has obvious heat-affected zone （HAZ）, while the HAZ of LBW joint is almost invisible. The X-ray diffraction result shows that the phase compositions of both joints are austenitic and no phase transition occurs. Energy disper- sive spectrometry result shows that there is violent evaporation of Mn element in LBW joint, while the proportion of Mn element in GTAW joint is almost unchanged. Tensile tests and micro-hardness measurements were performed to take into account the mechanical properties of joints manufactured by the two different processes. The micro-hard- ness profiles of both joints present a typical saddle distribution, and the hardness of GTAW seam is lower than that of LBW seam. The failure positions of LBW joints are all located in base metal while the GTAW joints are all at the weld toe due to the softening of HAZ. By means of scanning electron microscopy, a typical ductile fracture is observed in LBW joint, while a brittle fracture with quasi-cleavage fracture characteristic is observed in GTAW joint.
基金the National Natural Science Foundation of China （No. 50575022） Specialized Research Foundation for the Doctoral Program of Higher Education （No. 20040008024）.
文摘The influence of cold rolling reduction on microstructure and mechanical properties of the TWIP （ttwinning induced plasticity） steel was investigated. The results＇ indicated that the steel had better comprehensive mechanical properties when cold rolling reduction was about 65.0% and the annealing temperature was 1000℃. The tensile strength of the steel is about 640MPa and the yield strength is higher than 255MPa, while the elongation is＇ above 82%. The microstructure is composed of austenitic matrix and annealing twins at room temperature, at the same time, a significant amount of annealing twins and stacking faults＇ are observed by transmission electron microscopy （TEM）. Mechanical twins play a dominant role during deformation, and result in exceUent mechanical properties.
文摘The aim of the present work was to study the effect of austenite grain size （AGS） on the martensite formation in a high-manganese twinning-induced plasticity （TWIP） steel. The results of a quantitative microstructural characterization of the steel by the whole X-ray pattern fitting Rietveld software, materials analysis using diffraction （MAUD）, indicated that the volume fraction of αbcc-martensite increases with increasing AGS. However, the value of the stacking fault probability （Psf） does not show a large variation for samples with different values of AGS under water-quenching conditions.
文摘The dynamic mechanical properties of Fe-30Mn-3Si-4A1 twinning induced plasticity （TWIP） steel were studied by the split-Hopkinson pressure bar （SHPB） at temperatures of 298-1073 K and strain rates of 700, 2500, and 5000 s-1. The TWIP steel indicates strain rate hardening effect between 700 and 2500 s-1, but it shows strain rate softening effect between 2500 and 5000 s-1. In addition, the strain rate softening effect enhances with an increase in deformation temperature. After deformation, the microstructures were studied by optical microscopy （OM）. It is shown that the deformation bands become more convergence, a part of which become interwoven with an increase in strain rate, and the dynamic recovery and recrystallization are enhanced with an increase in both temperature and strain rate.
文摘Mechanical properties and microstructural evolution of the hot-rolled Fe-Mn-C-Si TWIP steel were investigated and the deformation mechanism was analyzed.The results showed that the tensile strength and elongation were about 1050 MPa and 60%,respectively.The hot-rolled steel had high specific energy absorption and impact toughness between-120 ℃ and 20 ℃.Some inhomogeneous dislocation zones were observed in the undeformed steel.Lots of deformation twins and twin-dislocation interactions were observed in the deformed steel.TWIP effect was the major deformation mechanism for the excellent mechanical properties.
基金Item Sponsored by National Natural Science Foundation of China(51374151,21201129)Science and Technology Major Project of Shanxi Province of China(20111101053)Natural Science Foundation of Shanxi Province of China(2011011020-2)
文摘The fatigue performance and fracture mechanism of laser welded twinning induced plasticity（TWIP）steel joint were investigated experimentally based on the evolution of microstructure and micromechanical properties.The optical microscopy was used to analyze the evolution of microstructure.The variation of composition and phase structure of fusion zone were detected by energy dispersive X-ray and X-ray diffraction spectrometers.The micromechanical behaviors of the various zones were characterized using nanoindentation.The static tensile test and high cycle fatigue test were performed to evaluate the mechanical properties of welded joint and base metal.The microstructures,tensile properties and fatigue strength of base metal as well as welded metal were analyzed.The fatigue fracture surfaces of base metal and welded joint were observed by means of scanning electron microscopy,in order to identify fatigue crack initiation sites and propagation mechanisms.Moreover,the fatigue fracture characteristics and mechanisms for the laser welded TWIP steel joints were analyzed.
基金Funded by the National Natural Science Foundation of China(Nos.51701206 and 51671187)the Shanxi Natural Science Foundation(No.2019JQ-833)+2 种基金the Anhui Natural Science Foundation(1808085QE166)the Special Scientific Research Project of Shanxi Education Committee(No.19JQ0974)the Doctoral Research Initiation Project of Yan’an University(No.YDBD2018-21)。
文摘The mechanical behavior and microstructural evolution of an Fe-30Mn-3Al-3Si twinninginduced plasticity(TWIP)steel processed using warm forging was investigated.It is found that steel processed via warm forging improves comprehensive mechanical properties compared to the TWIP steel processed via cold rolling,with a high tensile strength(R_(m))of 793 MPa,a yield strength(R_(P))of 682 MPa,an extremely large R_(P)/R_(m)ratio as high as 0.86 as well as an excellent elongation rate of 46.8%.The microstructure observation demonstrates that steel processed by warm forging consists of large and elongated grains together with fine,equiaxed grains.Complicated micro-defect configurations were also observed within the steel,including dense dislocation networks and a few coarse deformation twins.As the plastic deformation proceeds,the densities of dislocations and deformation twins significantly increase.Moreover,a great number of slip lines could be observed in the elongated grains.These findings reveal that a much more dramatic interaction between microstructural defect and dislocations glide takes place in the forging sample,wherein the fine and equiaxed grains propagated dislocations more rapidly,together with initial defect configurations,are responsible for enhanced strength properties.Meanwhile,larger,elongated grains with more prevalently activated deformation twins result in high plasticity.
基金funded by the National Natural Science Foundation of China(Nos.92266206,52227810)Jilin Province Science and Technology Development Plan(No.YDZJ202101ZYTS129)the Fundamental Research Funds for the Central Universities(No.2022-JCXK-11).
文摘Graphene(Gr)reinforced high-entropy alloy(HEA)matrix composites are expected as potential candidates for next-generation structural applications in light of outstanding mechanical properties.A deep comprehension of the underlying deformation mechanisms under extreme shock loading is of paramount importance,however,remains lacking due to experimentally technical limitations in existence.In the present study,by means of nonequilibrium molecular dynamics simulations,dynamic deformation behaviors and corresponding mechanisms in equiatomic FeNiCrCoCu HEA/Gr composite systems were investigated in terms of various shock velocities.The resistance to dislocation propagation imparted by Gr was corroborated to encourage the elevated local stress level by increasing the likelihood of dislocation interplays,which facilitated the onset of twins and hexagonal close-packed(HCP)martensite laths.Meanwhile,the advent of Gr was demonstrated to endow the HEA with an additional twinning pathway that induced a structural conversion from HCP to parent face-centered cubic(FCC)inside HCP martensite laths,different from the classical one that necessitated undergoing the intermediate procedure of extrinsic stacking fault(ESF)evolution.More than that,by virtue of an increase in flow stress,the transformation-induced plasticity(TRIP)effect was validated to be additionally evoked as the predominant strain accommodation mechanism at higher strains on the one hand,but which only assisted plasticity in pure systems,and on the other hand,can also act as an auxiliary regulation mode together with the twinning-induced plasticity(TWIP)effect under intermediate strains,but with enhanced contributions relative to pure systems.One may expect that TRIP and TWIP effects promoted by introducing Gr would considerably inspire a synergistic effect between strength and ductility,contributing to the exceptional shock-resistant performance of FeNiCrCoCu HEAs under extreme regimes.
文摘As twinning-induced plasticity （TWIP） steel is one potential material for shaped charge liner due to the combination of high strength and high plasticity, deformation mechanism at high strain rate and high temperature is required to study. Compression experiments of Fe 30Mn-3Si-4Al TWIP steel were conducted using a Gleeble 1500 thermal simulation machine and a split-Hopkinson pressure bar （SHPB） between 298 and 1073 K at strain rates of 10 3 and 700 s-1 , respectively. Microstructures were observed using optical microscopy （OM） and transmission e- lectron microscopy （TEM）. Results show that flow stress and densities of deformation twins and dislocations de crease with increasing deformation temperature at strain rates of 10 3 and 700 s -1. The stack fault energy （SFE） values （Г） of Fe-30Mn-3Si-4Al TWIP steel at different temperatures were calculated using thermodynamic data. Based on corresponding microstructures, it can he inferred that at 700 s -1 , twinning is the main deformation mecha- nism at 298-573 K for 30 mJ/m2≤Г≤63 mJ/m2 , while dislocation gliding is the main deformation mechanism above 1 073 K for Г≥145 mJ/m2. In addition, with increasing strain rate from 10-3 to 700 s -1 , the SFE range of twinning is enlarged and the SEF value of twinning becomes higher.
基金supported by the National High-Tech Research and Development Program of China (No.2008AA03E502)the Science and Technology Support Program of China (No.2006BAE03A06)
文摘The microstructure and crack behaviour of twinning induced plasticity （TWIP） steel during tensile deformation was investigated with in-situ scanning electron microscopy （SEM）. The results show that there are two modes of plastic deformation during tensile test in the Fe-Mn-C TWIP steel： dislocation gliding and deformation twins. During the process of tensile deformation, secondary deformed twins are found. Inclusions have played a role in the course of ductile fracture, and microcracks initiate from inclusions and twin-twin intersections.
