N. Bhowmik, Saroj Kumar Ghosh, S. Mandal, A. Haldar, P. Chattopadhyay
An excellent strength-ductility combination offered by martensite-austenite microstructure in medium-Mn steels draws special attention for automotive applications. However, yielding of the steel is often compromised in the form of serration, with a jerky metal flow and deformation banding, by the reason yet to be settled. Thus as per the practice, a hot-rolled sheet after intercritical annealing at 650 °C is subjected to the current investigation. The intercritical annealing reveals an undissolved-unoccupied state attained by carbon, which readily interacts with the sample dislocations introduced in the microstructure during the prior processing. The interaction forms Cottrell atmospheres at annealing temperature rather than at room temperature as enumerated in metal plasticity theory, and hence, finds the clue for hitherto unexplored mechanism of dynamic strain aging. Accordingly, when fresh dislocations intercept barriers laid by the carbon-dislocation aggregates into clusters in advance, the interaction triggers serration for the proposed mechanism.
{"title":"Genesis of Plasticity-Induced Serrated Metal Flow in Medium-Mn Steel","authors":"N. Bhowmik, Saroj Kumar Ghosh, S. Mandal, A. Haldar, P. Chattopadhyay","doi":"10.2139/ssrn.3742930","DOIUrl":"https://doi.org/10.2139/ssrn.3742930","url":null,"abstract":"An excellent strength-ductility combination offered by martensite-austenite microstructure in medium-Mn steels draws special attention for automotive applications. However, yielding of the steel is often compromised in the form of serration, with a jerky metal flow and deformation banding, by the reason yet to be settled. Thus as per the practice, a hot-rolled sheet after intercritical annealing at 650 °C is subjected to the current investigation. The intercritical annealing reveals an undissolved-unoccupied state attained by carbon, which readily interacts with the sample dislocations introduced in the microstructure during the prior processing. The interaction forms Cottrell atmospheres at annealing temperature rather than at room temperature as enumerated in metal plasticity theory, and hence, finds the clue for hitherto unexplored mechanism of dynamic strain aging. Accordingly, when fresh dislocations intercept barriers laid by the carbon-dislocation aggregates into clusters in advance, the interaction triggers serration for the proposed mechanism.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129627477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Wang, R. K. Nutor, Y.X. Li, Q. Cao, S. Ding, X.D. Wang, D.X. Zhang, J. Jiang
The single-phase face-centered cubic (FCC) high entropy alloys (HEAs) with remarkable ductility but lower strength, limiting the engineering application in a wide range. The ductility-strength trade-off could be addressed by tuning the constituent and chemical composition to lower stacking fault energy (SFE) and introduce additional strain-hardening strategies. In this work, a series of non-equiatomic (Co 40 Fe 25 Cr 20 Ni 15 ) 95 Al 5 HEAs annealed by flash electro-pulsing treatments at different voltages, was prepared with the incorporation of deformation twining during plastic deformation. The 130 V-annealed sample demonstrated a good combination of tensile strength of 0.96 GPa and ductility of 16.5%, while the 150 V-annealed alloy showed dramatically increased ductility of 49.2%. The higher Hall-Petch coefficient k H ( K σy ) value of 341.6 (828.8) and the thinner deformation twins spacing was responsible for the improved tensile strength for 130 V-samples. Moreover, more stacking faults and deformation twins in 150 V-sample accommodated more plastic and delayed the fracture, resulting increased ductility. This work provides a fast-effective method to tune the mechanical properties of non-equiatomic HEAs by adjusting the annealing voltage and achieved in a minute, which might open the avenue for future industrial application.
单相面心立方(FCC)高熵合金(HEAs)塑性好，但强度较低，限制了其在工程上的广泛应用。可以通过调整成分和化学成分来降低层错能(SFE)并引入额外的应变硬化策略来解决延展性和强度之间的权衡。本文制备了一系列非等原子(Co 40 Fe 25 Cr 20 Ni 15) 95 Al 5 HEAs，并在塑性变形过程中掺入变形缠绕。经130 v退火后，合金的抗拉强度为0.96 GPa，延展性为16.5%，而经150 v退火后，合金的延展性显著提高，达到49.2%。增大的Hall-Petch系数k H (k σy)值为341.6(828.8)，减小变形孪晶间距是提高130 v试样抗拉强度的主要原因。另外，150v试样中更多的层错和变形孪晶容纳了更多的塑性，延迟了断裂，从而提高了延性。本工作提供了一种快速有效的方法，通过调整退火电压来调整非等原子HEAs的机械性能，并在一分钟内实现，为未来的工业应用开辟了道路。
{"title":"Tuning Mechanical Properties of High Entropy Alloys by Electro-Pulsing Method","authors":"N. Wang, R. K. Nutor, Y.X. Li, Q. Cao, S. Ding, X.D. Wang, D.X. Zhang, J. Jiang","doi":"10.2139/ssrn.3932309","DOIUrl":"https://doi.org/10.2139/ssrn.3932309","url":null,"abstract":"The single-phase face-centered cubic (FCC) high entropy alloys (HEAs) with remarkable ductility but lower strength, limiting the engineering application in a wide range. The ductility-strength trade-off could be addressed by tuning the constituent and chemical composition to lower stacking fault energy (SFE) and introduce additional strain-hardening strategies. In this work, a series of non-equiatomic (Co 40 Fe 25 Cr 20 Ni 15 ) 95 Al 5 HEAs annealed by flash electro-pulsing treatments at different voltages, was prepared with the incorporation of deformation twining during plastic deformation. The 130 V-annealed sample demonstrated a good combination of tensile strength of 0.96 GPa and ductility of 16.5%, while the 150 V-annealed alloy showed dramatically increased ductility of 49.2%. The higher Hall-Petch coefficient k H ( K σy ) value of 341.6 (828.8) and the thinner deformation twins spacing was responsible for the improved tensile strength for 130 V-samples. Moreover, more stacking faults and deformation twins in 150 V-sample accommodated more plastic and delayed the fracture, resulting increased ductility. This work provides a fast-effective method to tune the mechanical properties of non-equiatomic HEAs by adjusting the annealing voltage and achieved in a minute, which might open the avenue for future industrial application.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"509 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134289067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Fatigue resistance is invariably critical for structural materials, but is rarely considered in the development of new bioinspired materials. Here the fatigue behavior and damage mechanisms of a nacre-like ceramic (yttria-stabilized zirconia) - polymer (polymethyl methacrylate) composite, which resembles human tooth enamel in its stiffness and hardness, were investigated under cyclic compression to simulate potential service conditions. The composite has a brick-and-mortar structure which exhibits a staircase-like fracture behavior; it displays a transition in cracking mode from the fracture of the ceramic bricks to separation along the inter-brick polymer phase with increasing stress amplitude. The nacre-like structure functions to induce crack deflection, increase the roughness of the crack surfaces, and promote the mutual sliding between bricks during fracture; this results in high fatigue resistance, which enhances the potential of this composite for dental applications.
{"title":"Compression Fatigue Properties and Damage Mechanisms of a Bioinspired Nacre-Like Ceramic-Polymer Composite","authors":"Guoqi Tan, Qin Yu, Zengqian Liu, Xuegang Wang, Mingyang Zhang, Yanyan Liu, Zhefeng Zhang, R. Ritchie","doi":"10.2139/ssrn.3860384","DOIUrl":"https://doi.org/10.2139/ssrn.3860384","url":null,"abstract":"Abstract Fatigue resistance is invariably critical for structural materials, but is rarely considered in the development of new bioinspired materials. Here the fatigue behavior and damage mechanisms of a nacre-like ceramic (yttria-stabilized zirconia) - polymer (polymethyl methacrylate) composite, which resembles human tooth enamel in its stiffness and hardness, were investigated under cyclic compression to simulate potential service conditions. The composite has a brick-and-mortar structure which exhibits a staircase-like fracture behavior; it displays a transition in cracking mode from the fracture of the ceramic bricks to separation along the inter-brick polymer phase with increasing stress amplitude. The nacre-like structure functions to induce crack deflection, increase the roughness of the crack surfaces, and promote the mutual sliding between bricks during fracture; this results in high fatigue resistance, which enhances the potential of this composite for dental applications.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133121136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The underlying mechanism of discontinuous yielding behavior in an ultrafine-grained (UFG) Fe-31Mn-3Al-3Si (wt.%) austenitic TWIP steel was investigated by the use of advanced TEM technique with taking the plastic deformation mechanisms and their correlation with grains size near the macroscopic yield point into account. Typical yield drop mechanisms such as the dislocation locking by the Cottrell atmosphere due to the presence of interstitial impurities cannot explain the origin of this phenomenon in the UFG high-Mn austenitic TWIP steel. Here, we experimentally revealed that the plastic deformation mechanisms in the early stage of deformation, around the macroscopic yield point, show an obvious association with grain size. More specifically, the main mechanism shifts from the conventional slip in grain interior to twinning nucleated from grain boundaries with decreasing the grain size down to less than 1 μm. Our observation indicates that the grain size dependent deformation mechanisms transition is also deeply associated with the discontinuous yielding behavior as it could govern the changes in the grain interior dislocation density of mobile dislocations around the macroscopic yield point.
{"title":"Grain Size Altering Yielding Mechanisms in Ultrafine Grained High-Mn Austenitic Steel: Advanced TEM Investigations","authors":"Chang-Yu Hung, Y. Bai, N. Tsuji, M. Murayama","doi":"10.2139/ssrn.3681163","DOIUrl":"https://doi.org/10.2139/ssrn.3681163","url":null,"abstract":"Abstract The underlying mechanism of discontinuous yielding behavior in an ultrafine-grained (UFG) Fe-31Mn-3Al-3Si (wt.%) austenitic TWIP steel was investigated by the use of advanced TEM technique with taking the plastic deformation mechanisms and their correlation with grains size near the macroscopic yield point into account. Typical yield drop mechanisms such as the dislocation locking by the Cottrell atmosphere due to the presence of interstitial impurities cannot explain the origin of this phenomenon in the UFG high-Mn austenitic TWIP steel. Here, we experimentally revealed that the plastic deformation mechanisms in the early stage of deformation, around the macroscopic yield point, show an obvious association with grain size. More specifically, the main mechanism shifts from the conventional slip in grain interior to twinning nucleated from grain boundaries with decreasing the grain size down to less than 1 μm. Our observation indicates that the grain size dependent deformation mechanisms transition is also deeply associated with the discontinuous yielding behavior as it could govern the changes in the grain interior dislocation density of mobile dislocations around the macroscopic yield point.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"143 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114138285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Mishra, R. Sarkar, Vajinder Singh, A. Mukhopadhyay, Rohit T. Mathew, V. Madhu, M. Prasad
Abstract The feasibility of significant weight reduction in conjunction with the superior strength-ductility combination makes Fe-Mn-Al-C-based steels the candidate material for automotive and structural applications. The alloy chemistry and processing conditions influence the microstructure in low-density steels (LDS); however, their role in deformation behaviour is not fully understood. In the present study, three different austenitic LDS grades viz. Fe-28Mn-9Al-0.9C, Fe-28Mn-9Al-5Ni-0.9C and Fe-15Mn-9Al-5Ni-0.9C alloys in hot-rolled conditions were used for evaluating the role of secondary phases, especially B2 ordered Fe(Ni)Al phase on deformation characteristics. Ni-free LDS microstructure consisted of the γ-matrix with fine κ-carbides, whereas Ni containing low Mn alloy possessed coarser κ-carbides along with B2 in both bamboo-like stringer and polygonal particle morphology in the γ-matrix. The B2 containing alloy exhibited higher strength with reduced tensile ductility than the B2-free alloy. Hardness of the γ-matrix and B2 phase were similar with B2 grains exhibiting distinct pop-in events in the nanoindentation curves indicating incipient plasticity. The γ-matrix and B2 co-deform near yield, and a favourable orientation relationship (OR) between the γ-matrix and B2 facilitated easy slip transfer, while the non-favourable OR controlled ductility by strain accumulation and B2-cracking. The differences in the strain hardening behaviour of B2-free and B2 containing alloys were elucidated based on the changes in dislocation substructure evolution examined by an automated crystal orientation mapping in electron microscopy.
{"title":"Microstructure and Deformation Behaviour of Austenitic Low-Density Steels: The Defining Role of B2 Intermetallic Phase","authors":"B. Mishra, R. Sarkar, Vajinder Singh, A. Mukhopadhyay, Rohit T. Mathew, V. Madhu, M. Prasad","doi":"10.2139/ssrn.3831019","DOIUrl":"https://doi.org/10.2139/ssrn.3831019","url":null,"abstract":"Abstract The feasibility of significant weight reduction in conjunction with the superior strength-ductility combination makes Fe-Mn-Al-C-based steels the candidate material for automotive and structural applications. The alloy chemistry and processing conditions influence the microstructure in low-density steels (LDS); however, their role in deformation behaviour is not fully understood. In the present study, three different austenitic LDS grades viz. Fe-28Mn-9Al-0.9C, Fe-28Mn-9Al-5Ni-0.9C and Fe-15Mn-9Al-5Ni-0.9C alloys in hot-rolled conditions were used for evaluating the role of secondary phases, especially B2 ordered Fe(Ni)Al phase on deformation characteristics. Ni-free LDS microstructure consisted of the γ-matrix with fine κ-carbides, whereas Ni containing low Mn alloy possessed coarser κ-carbides along with B2 in both bamboo-like stringer and polygonal particle morphology in the γ-matrix. The B2 containing alloy exhibited higher strength with reduced tensile ductility than the B2-free alloy. Hardness of the γ-matrix and B2 phase were similar with B2 grains exhibiting distinct pop-in events in the nanoindentation curves indicating incipient plasticity. The γ-matrix and B2 co-deform near yield, and a favourable orientation relationship (OR) between the γ-matrix and B2 facilitated easy slip transfer, while the non-favourable OR controlled ductility by strain accumulation and B2-cracking. The differences in the strain hardening behaviour of B2-free and B2 containing alloys were elucidated based on the changes in dislocation substructure evolution examined by an automated crystal orientation mapping in electron microscopy.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122398483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During pregnancy, the fetal membrane (FM) is subjected to mechanical stretching that may result in preterm labor. The structural integrity of the FM is maintained by its collagenous layer. The disconnection and reconnection of molecular bonds between collagen fibrils are the fundamental processes that govern the irreversible mechanical and supermolecular changes in the FM. Here, we study the activation enthalpy of interfibrillar bonds in ex-vivo human FM. We analyze the strain-rate and temperature dependence of the irreversible deformations in FM subjected to inflation tests, which apply mechanical conditions similar to those experienced by the FM prior to and during the initiation of labor contractions. The obtained activation enthalpy of interfibrillar bonds matches the typical enthalpy values of polyvalent ionic bonds, implying on another important role that ions like Ca and Mg may play in the gestation and labor.
{"title":"Enthalpy of Collagen Interfibrillar Bonds in Fetal Membranes","authors":"Y. Marom, S. Gengrinovitch, E. Shalev, D. Shilo","doi":"10.2139/ssrn.3592060","DOIUrl":"https://doi.org/10.2139/ssrn.3592060","url":null,"abstract":"During pregnancy, the fetal membrane (FM) is subjected to mechanical stretching that may result in preterm labor. The structural integrity of the FM is maintained by its collagenous layer. The disconnection and reconnection of molecular bonds between collagen fibrils are the fundamental processes that govern the irreversible mechanical and supermolecular changes in the FM. Here, we study the activation enthalpy of interfibrillar bonds in ex-vivo human FM. We analyze the strain-rate and temperature dependence of the irreversible deformations in FM subjected to inflation tests, which apply mechanical conditions similar to those experienced by the FM prior to and during the initiation of labor contractions. The obtained activation enthalpy of interfibrillar bonds matches the typical enthalpy values of polyvalent ionic bonds, implying on another important role that ions like Ca and Mg may play in the gestation and labor.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124970471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Xiong, N. Grilli, Phani S. Karamched, B. Li, E. Tarleton, A. Wilkinson
Digital image correlation (DIC) and crystal plasticity simulation were utilised to study cold dwell behaviour in a coarse grain Ti-6Al alloy at 3 different temperatures up to 230 °C. Strains extracted from large volume grains were measured during creep by DIC and were used to calibrate the crystal plasticity model. The values of critical resolved shear stresses (CRSS) of the two main slip systems (basal and prismatic) were determined as a function of temperature. Stress along paths across the boundaries of two grain pairs, (1) a `rogue' grain pair and (2) a `non-rogue' grain pair, were determined at different temperatures. Load shedding was observed in the `rogue' grain pair, where a stress increment during the creep period was found in the `hard' grain. At elevated temperatures, 120 °C was found to be the worst case scenario as the stress difference at the grain boundaries of these two grain pairs were found to be the largest among the three temperatures. This can be attributed to the fact that the strain rate sensitivity of both prismatic and basal slip systems is at its greatest in this worst case scenario temperature.
{"title":"Cold Dwell Behaviour of Ti6Al Alloy: Understanding Load Shedding Using Digital Image Correlation and Crystal Plasticity Simulations","authors":"Y. Xiong, N. Grilli, Phani S. Karamched, B. Li, E. Tarleton, A. Wilkinson","doi":"10.2139/ssrn.3862135","DOIUrl":"https://doi.org/10.2139/ssrn.3862135","url":null,"abstract":"Digital image correlation (DIC) and crystal plasticity simulation were utilised to study cold dwell behaviour in a coarse grain Ti-6Al alloy at 3 different temperatures up to 230 °C. Strains extracted from large volume grains were measured during creep by DIC and were used to calibrate the crystal plasticity model. The values of critical resolved shear stresses (CRSS) of the two main slip systems (basal and prismatic) were determined as a function of temperature. Stress along paths across the boundaries of two grain pairs, (1) a `rogue' grain pair and (2) a `non-rogue' grain pair, were determined at different temperatures. Load shedding was observed in the `rogue' grain pair, where a stress increment during the creep period was found in the `hard' grain. At elevated temperatures, 120 °C was found to be the worst case scenario as the stress difference at the grain boundaries of these two grain pairs were found to be the largest among the three temperatures. This can be attributed to the fact that the strain rate sensitivity of both prismatic and basal slip systems is at its greatest in this worst case scenario temperature.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128977863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lei Ding, Yumei Zhou, Yangyang Xu, Pengfei Dang, Xiangdong Ding, Jun Sun, T. Lookman, D. Xue
In the present study, the reversible adiabatic temperature change (ΔTad) of shape memory alloys was shown to be proportional to the mechanical work released by the reverse martensitic transformation during unloading (ΔWu). As there exists a considerable amount of data (ΔWu) on superelastic stress-strain measurements in shape memory alloys, the proposed relationship allows us to predict ΔTad without caloric measurements. The estimated ΔTad from the ΔWu of different Ti-Ni alloys shows good linear relationship with the directly measured values. Moreover, following such a design criterion and by tuning of composition and thermo-mechanical treatment, a group of Ti-Ni binary shape memory alloys with a directly measured ΔTad larger than 35 K under tension were achieved. The large ΔTad and ΔWu can be ascribed to the grain refinement and the heterogeneous internal stress fields after the thermo-mechanical treatment, which have enhanced the critical stress of superelasticity and recoverability of martensitic transformation during unloading.
{"title":"Learning from Superelasticity Data to Search for Ti-Ni Alloys with Large Elastocaloric Effect","authors":"Lei Ding, Yumei Zhou, Yangyang Xu, Pengfei Dang, Xiangdong Ding, Jun Sun, T. Lookman, D. Xue","doi":"10.2139/ssrn.3844696","DOIUrl":"https://doi.org/10.2139/ssrn.3844696","url":null,"abstract":"In the present study, the reversible adiabatic temperature change (ΔTad) of shape memory alloys was shown to be proportional to the mechanical work released by the reverse martensitic transformation during unloading (ΔWu). As there exists a considerable amount of data (ΔWu) on superelastic stress-strain measurements in shape memory alloys, the proposed relationship allows us to predict ΔTad without caloric measurements. The estimated ΔTad from the ΔWu of different Ti-Ni alloys shows good linear relationship with the directly measured values. Moreover, following such a design criterion and by tuning of composition and thermo-mechanical treatment, a group of Ti-Ni binary shape memory alloys with a directly measured ΔTad larger than 35 K under tension were achieved. The large ΔTad and ΔWu can be ascribed to the grain refinement and the heterogeneous internal stress fields after the thermo-mechanical treatment, which have enhanced the critical stress of superelasticity and recoverability of martensitic transformation during unloading.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133079048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advanced manufacturing (AM) technologies, such as nanoscale additive manufacturing process, enable the fabrication of nanoscale architected materials which has received great attention due to their prominent properties. However, few studies delve into the functional gradient cellular architecture on nanoscale. This work studied the gradient nano-Gyroid architected material made of copper (Cu) by molecular dynamic (MD) simulations. The result reveals that, unlike homogeneous architecture, gradient Gyroid not only shows novel layer-by-layer deformation behaviour, but also processes significantly better energy absorption ability. Moreover, this deformation behaviour and energy absorption are predictable and designable, which demonstrate its highly programmable potential.
{"title":"Mechanical Properties of Gradient Copper Nano-Gyroid Cellular Structures: A Molecular Dynamics Study","authors":"Rui Dai, Dawei Li, Yunlong Tang","doi":"10.2139/ssrn.3538809","DOIUrl":"https://doi.org/10.2139/ssrn.3538809","url":null,"abstract":"Advanced manufacturing (AM) technologies, such as nanoscale additive manufacturing process, enable the fabrication of nanoscale architected materials which has received great attention due to their prominent properties. However, few studies delve into the functional gradient cellular architecture on nanoscale. This work studied the gradient nano-Gyroid architected material made of copper (Cu) by molecular dynamic (MD) simulations. The result reveals that, unlike homogeneous architecture, gradient Gyroid not only shows novel layer-by-layer deformation behaviour, but also processes significantly better energy absorption ability. Moreover, this deformation behaviour and energy absorption are predictable and designable, which demonstrate its highly programmable potential.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129885726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The internal twin-boundaries in lamellar γ-TiAl alloys, namely true-twin (TT), rotational boundary(RB), and pseudo-twin (PT), are known to be effective in strengthening the TiAl microstructures. Nevertheless, for designing microstructures with optimised mechanical properties, a better understanding of the role of these boundaries on fracture behavior is still required. To this end, we study how and to what degree crack advancement is affected by the local lattice orientation and atomic structure at the various twin boundaries. Molecular statics simulations were performed in conjunction with a linear elastic fracture mechanics based analysis, to understand the inter-lamellar and as well as trans-lamellar crack advancement at a TT, RB, and PT interface. The fracture toughness as well as the crack advancement mechanisms of the inter-lamellar cracks depend critically on the propagation direction. For instance, cracks along ⟨11‾2] in the TT, RB, and PT plane always emit dislocations at the crack tip, while the cracks along the opposite direction are brittle in nature. When it comes to trans-lamellar crack advancement, the crack tip shows significant plastic deformation and toughening for all inter-faces. However, at a TT, a brittle crack is able to penetrate through the interface at a higher applied load, and propagates in the adjacent γ′ phase, while in the case of RB and PT, the crack tip is blunted and arrested at or near the boundary, resulting in dislocation emission and crack tip toughening. This suggests that a variation of the sequence of the different rotational boundaries could be a possibility to tune the crack tip plasticity and toughening in lamellar TiAl.
{"title":"Twin-Boundary Assisted Crack Tip Plasticity and Toughening in Lamellar γ-TiAl","authors":"A. Neogi, R. Janisch","doi":"10.2139/ssrn.3790079","DOIUrl":"https://doi.org/10.2139/ssrn.3790079","url":null,"abstract":"The internal twin-boundaries in lamellar γ-TiAl alloys, namely true-twin (TT), rotational boundary(RB), and pseudo-twin (PT), are known to be effective in strengthening the TiAl microstructures. Nevertheless, for designing microstructures with optimised mechanical properties, a better understanding of the role of these boundaries on fracture behavior is still required. To this end, we study how and to what degree crack advancement is affected by the local lattice orientation and atomic structure at the various twin boundaries. Molecular statics simulations were performed in conjunction with a linear elastic fracture mechanics based analysis, to understand the inter-lamellar and as well as trans-lamellar crack advancement at a TT, RB, and PT interface. The fracture toughness as well as the crack advancement mechanisms of the inter-lamellar cracks depend critically on the propagation direction. For instance, cracks along ⟨11‾2] in the TT, RB, and PT plane always emit dislocations at the crack tip, while the cracks along the opposite direction are brittle in nature. When it comes to trans-lamellar crack advancement, the crack tip shows significant plastic deformation and toughening for all inter-faces. However, at a TT, a brittle crack is able to penetrate through the interface at a higher applied load, and propagates in the adjacent γ′ phase, while in the case of RB and PT, the crack tip is blunted and arrested at or near the boundary, resulting in dislocation emission and crack tip toughening. This suggests that a variation of the sequence of the different rotational boundaries could be a possibility to tune the crack tip plasticity and toughening in lamellar TiAl.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124568591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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