A secondary twinning orientation relationship between A and B martensite variants in aCuZnAl shape memory alloy was confirmed under TEM observation.The twin plane,(50),is a linear combination of (8)and(1 0 10)planes,w...A secondary twinning orientation relationship between A and B martensite variants in aCuZnAl shape memory alloy was confirmed under TEM observation.The twin plane,(50),is a linear combination of (8)and(1 0 10)planes,which are twin planes ofA:C and A:D type pair respectively.展开更多
Deformation twinning is profusely activated in the Mg alloys due to lower critical resolved shear stress(CRSS) compared to the non-basal slip systems(prismatic and pyramidal ) and plays a significant role in texture r...Deformation twinning is profusely activated in the Mg alloys due to lower critical resolved shear stress(CRSS) compared to the non-basal slip systems(prismatic and pyramidal ) and plays a significant role in texture reorientation, grain refinement and enhancement of mechanical performance. Twinning is a sequential process comprising twin nucleation, twin propagation and twin growth, hence several intrinsic and extrinsic parameters that facilitate or suppress the process have been critically reviewed. The dependence of twinning on the grain size, deformation temperature, favorable grain orientation and shear strain have been thoroughly discussed in the context of published literature and an attempt has been made to provide a benchmark conclusive finding based on the majority of works. Furthermore, the subsequent effect of twinning on the mechanical performance of Mg alloys, including ductility, formability and tension-compression asymmetry has been discussed in detail. Lastly, the stability of twins, including stress and thermal stability, is summarized and critical issues related to pertinent bottlenecks have been addressed.展开更多
We investigated the asymmetric tension-compression(T-C)behavior of ZA21 bars with bimodal and uniform structures through axial tension and compression tests.The results show that the yield strengths of bars having bim...We investigated the asymmetric tension-compression(T-C)behavior of ZA21 bars with bimodal and uniform structures through axial tension and compression tests.The results show that the yield strengths of bars having bimodal structure are 206.42 and 140.28 MPa under tension and compression,respectively,which are higher than those of bars having uniform structure with tensile and compressive yield strength of 183.71 and 102.86 MPa,respectively.Prismatic slip and extension twinning under tension and basal slip and extension twinning under compression dominate the yield behavior and induce the T-C asymmetry.However,due to the basal slip activated in fine grains under tension and the inhibition of extension twinning by fine grains under compression,the bimodal structure possesses a lower T-C asymmetry(0.68)compared to the uniform structure(0.56).Multiple extension twins occur during deformation,and the selection of twin variants depends on the Schmid factor of the six variants activated by parent grains.Furthermore,the strengthening effect of the bimodal structure depends on the grain size and the ratio of coarse and fine grains.展开更多
Twinned substructure in lath martensite was induced in the interstitial free(IF)steel via a high pressure thermal cycle(heating up to 1100℃and holding for 30 min,cooling at 10℃/s to room temperature under a pressure...Twinned substructure in lath martensite was induced in the interstitial free(IF)steel via a high pressure thermal cycle(heating up to 1100℃and holding for 30 min,cooling at 10℃/s to room temperature under a pressure of 4 GPa).Experimental observations and theoretical simulation confrm that the twinned substructure has the origin related to the twinned variants rather than the bcc{112}<111>twins,while extra difraction spots were caused by crystal overlapping rather than any extra phase.The diferences in crystallography and electron difraction behavior between twinned variants and{112}<111>twins were discussed in detail.展开更多
Deformation twinning serves as an important mode of plastic dissipation processes in nanoscale body-centered cubic(BCC)metals,but its origin and spatio-temporal features are mysterious.Here,applying in situ tensile ex...Deformation twinning serves as an important mode of plastic dissipation processes in nanoscale body-centered cubic(BCC)metals,but its origin and spatio-temporal features are mysterious.Here,applying in situ tensile experiments,we report a strong size effect on mediating the twinning behaviors and twin boundary(TB)-dislocation interaction mechanisms in BCC iron(Fe)nanowires(NWs).There exists a critical diameter(d)of∼2.5 nm,above which the deformation twinning rather than dislocation slip dominates the plasticity.Unlike the traditional reflection TBs,the intermediate isosceles TBs are consis-tently observed as mediated by the 1/12<111>partial dislocations.Moreover,we uncover two distinct TB-related deformation mechanisms,including twin variant re-orientation and TB cracking for NWs with d<17 nm and d>17 nm,respectively.Further molecular dynamics and statics simulations provide the basic underlying mechanisms for size-dependent plasticity,which have been largely overlooked in previous experimental investigations.Our findings highlight the importance of grain size in mediating the deformation behaviors in Fe,serving as possible guidance for exploring single-crystalline and poly-crystalline Fe-based materials(e.g.steel)with optimized mechanical performance.展开更多
This paper proposes a direct and simple method to identify the second twins from twinning variants by electron back scattered diffraction(EBSD).To clarify the orientation relationship between the neighboring crystals,...This paper proposes a direct and simple method to identify the second twins from twinning variants by electron back scattered diffraction(EBSD).To clarify the orientation relationship between the neighboring crystals,the misorientation calculation by MATLAB software based on the EBSD data is also used.This method is generally applicable to predict the variants occurring in the nucleation and growth of the recrystallization or phase transformation process.展开更多
文摘A secondary twinning orientation relationship between A and B martensite variants in aCuZnAl shape memory alloy was confirmed under TEM observation.The twin plane,(50),is a linear combination of (8)and(1 0 10)planes,which are twin planes ofA:C and A:D type pair respectively.
基金supported by the National Research Foundation of Korea (NRF)grant funded by the Korean government (MSIT) (No.2020R1C1C1004434)。
文摘Deformation twinning is profusely activated in the Mg alloys due to lower critical resolved shear stress(CRSS) compared to the non-basal slip systems(prismatic and pyramidal ) and plays a significant role in texture reorientation, grain refinement and enhancement of mechanical performance. Twinning is a sequential process comprising twin nucleation, twin propagation and twin growth, hence several intrinsic and extrinsic parameters that facilitate or suppress the process have been critically reviewed. The dependence of twinning on the grain size, deformation temperature, favorable grain orientation and shear strain have been thoroughly discussed in the context of published literature and an attempt has been made to provide a benchmark conclusive finding based on the majority of works. Furthermore, the subsequent effect of twinning on the mechanical performance of Mg alloys, including ductility, formability and tension-compression asymmetry has been discussed in detail. Lastly, the stability of twins, including stress and thermal stability, is summarized and critical issues related to pertinent bottlenecks have been addressed.
基金financially supported by the National Natural Science Foundation of China (No. 52275305)the Fundamental Research Funds for the Central Universities (No. FRF-IC-20-10)the China Postdoctoral Science Foundation (No. 2021M700378)
文摘We investigated the asymmetric tension-compression(T-C)behavior of ZA21 bars with bimodal and uniform structures through axial tension and compression tests.The results show that the yield strengths of bars having bimodal structure are 206.42 and 140.28 MPa under tension and compression,respectively,which are higher than those of bars having uniform structure with tensile and compressive yield strength of 183.71 and 102.86 MPa,respectively.Prismatic slip and extension twinning under tension and basal slip and extension twinning under compression dominate the yield behavior and induce the T-C asymmetry.However,due to the basal slip activated in fine grains under tension and the inhibition of extension twinning by fine grains under compression,the bimodal structure possesses a lower T-C asymmetry(0.68)compared to the uniform structure(0.56).Multiple extension twins occur during deformation,and the selection of twin variants depends on the Schmid factor of the six variants activated by parent grains.Furthermore,the strengthening effect of the bimodal structure depends on the grain size and the ratio of coarse and fine grains.
基金supported by the National Natural Science Foundation of China(Nos.52171125,52071178)the Open Testing Funding of Large Instruments and Equipment of Southwest Jiaotong University,China(No.2022SRII-003)the Open Funding of International Joint Laboratory for Light Alloys(MOE),Chongqing University,China。
基金supported by the Natural Science Foundation-Steel and Iron Foundation of Hebei Province(No.E2021203051)the Hundred Outstanding Creative Talents Projects in Universities of Hebei Province,China,and the Project Program of Heavy Machinery Collaborative Innovation Center,China.
文摘Twinned substructure in lath martensite was induced in the interstitial free(IF)steel via a high pressure thermal cycle(heating up to 1100℃and holding for 30 min,cooling at 10℃/s to room temperature under a pressure of 4 GPa).Experimental observations and theoretical simulation confrm that the twinned substructure has the origin related to the twinned variants rather than the bcc{112}<111>twins,while extra difraction spots were caused by crystal overlapping rather than any extra phase.The diferences in crystallography and electron difraction behavior between twinned variants and{112}<111>twins were discussed in detail.
基金Projects(11272094,11072064)supported by the National Natural Science Foundation of ChinaProject(LGZX201101)supported by the Laboratory Center of Guangxi Science and Technology,ChinaProject(1074023)supported by the Science Foundation of Guangxi University of Science&Technology,China
基金supported by the National Natural Science Foundation of China (Nos.52071237,12074290,51871169,52101021,and 12104345)the Natural Science Foundation of Jiangsu Province (No.BK20191187)+1 种基金the Young Top-notch Talent Cultivation Program of Hubei Province,the Science and Technology Program of Shenzhen (No.JCYJ20190808150407522)the China Postdoctoral Science Foundation (No.2019M652685).
文摘Deformation twinning serves as an important mode of plastic dissipation processes in nanoscale body-centered cubic(BCC)metals,but its origin and spatio-temporal features are mysterious.Here,applying in situ tensile experiments,we report a strong size effect on mediating the twinning behaviors and twin boundary(TB)-dislocation interaction mechanisms in BCC iron(Fe)nanowires(NWs).There exists a critical diameter(d)of∼2.5 nm,above which the deformation twinning rather than dislocation slip dominates the plasticity.Unlike the traditional reflection TBs,the intermediate isosceles TBs are consis-tently observed as mediated by the 1/12<111>partial dislocations.Moreover,we uncover two distinct TB-related deformation mechanisms,including twin variant re-orientation and TB cracking for NWs with d<17 nm and d>17 nm,respectively.Further molecular dynamics and statics simulations provide the basic underlying mechanisms for size-dependent plasticity,which have been largely overlooked in previous experimental investigations.Our findings highlight the importance of grain size in mediating the deformation behaviors in Fe,serving as possible guidance for exploring single-crystalline and poly-crystalline Fe-based materials(e.g.steel)with optimized mechanical performance.
基金financially supported by the Natural Science Foundation of Liaoning Province, China (No. 2020-MS-004)the National Natural Science Foundation of China (Nos. 51601193, 51701218)+1 种基金the National Key Research and Development Program of China (No. 2016YFB0301104)the State Key Program of National Natural Science of China (No. 51531002)。
基金the National Natural Science Foundation of China(Nos.51401172 and 51601003)Fundamental Research Funds for the Central Universities,China(No.2682020ZT114)open funding of International Joint Laboratory for Light Alloys(MOE),Chongqing University,China。
基金financially supported by the National Natural Science Foundation of China (Nos.50901018 and 51304039)the Fundamental Research Funds for the Central Universities (No.N110402008)the Doctoral Fund of Ministry of Education of China (No.20090042120009)
文摘This paper proposes a direct and simple method to identify the second twins from twinning variants by electron back scattered diffraction(EBSD).To clarify the orientation relationship between the neighboring crystals,the misorientation calculation by MATLAB software based on the EBSD data is also used.This method is generally applicable to predict the variants occurring in the nucleation and growth of the recrystallization or phase transformation process.