Fe Mn C系TWIP钢的拉伸应变硬化行为研究

 通过试验研究了Fe Mn C系TWIP钢的拉伸应变硬化行为。结果表明：试验钢在拉伸过程中的应变硬化表现为阶段性多n值行为。其应变硬化机制有两种：在0.4%～3%的应变区间为位错强化阶段,10％～50%的应变区间为孪晶强化阶段。在这两个区间内n值皆为定值,而在4％～10％的应变区间n值呈不断上升趋势。     

TWIP钢的拉伸应变硬化行为

采用静态拉伸、金相组织观察方法研究了5种不同锰含量的TWIP钢的拉伸应变硬化行为.结果表明:5种钢的真应力与真应变不遵循Hollomond的线性关系,其中1号钢的应变硬化指数n值随真应变的增大先升后降,其它4种成分钢的n值随真应变的增大而提高.对于同一成分的钢,其n值均随应变速率的增大而减小.其微观变形机制是:随着锰含量的增加,孪晶形成逐渐起主导作用;拉伸前组织中有退火孪晶;随着变形的进行,产生大量的形变孪晶,孪晶与位错之间的交互作用与硬化率相协调,从而延迟了颈缩的产生,导致TWIP钢具有很高的均匀变形能力.     

Effect of Microstructure in TRIP Steel on Its Tensile Behavior at High Strain Rate

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10Ni5CrMoV船体钢拉伸性能的高应变速率效应

在1.6×10-3～1.2×103s-1的应变速率范围内,研究了应变速率对10Ni5CrMoV钢室温拉伸性能的影响.结果表明,应变速率对10Ni5CrMoV钢的断裂方式没有影响,拉伸试样均为塑性断裂,断裂微观机制主要是位错滑移;抗拉强度随应变速率增加而略有增加;伸长率随应变速率的增加先下降后上升,但总体无降低;高应变速率并未造成该钢的脆化.根据位错滑移机制对此进行了说明.     

应变速率对钛合金室温拉伸性能的影响

拉伸速率对金属材料的室温拉伸性能影响很大,文章介绍了不同应变速率对钛合金Ti6Al4V(TC4)、TA15和Ti1023室温拉伸性能影响的研究进展,并通过分析和归纳,阐述了第一应变速率和第二应变速率对钛合金的抗拉强度、屈服强度、断后伸长率及断面收缩率的影响程度和规律,最后对应变速率对钛合金室温拉伸性能影响研究的发展方向进行了展望。     

TWIP钢室温静态拉伸下的组织形态和变形机制

在室温下对退火Fe-24Mn-1Si-1.5Al-0.045CTWIP钢进行了不同程度的拉伸变形,采用JEM-2100透射电子显微镜对变形后的组织形貌进行表征和分析。研究结果表明:在变形初期,晶粒内存在着大量位错,它们相互缠结,呈胞状结构。在此阶段,位错滑移为主要变形机制。随着变形量的增加,形变孪晶在晶界等处形成,孪生机制被激活,孪生和滑移机制相互竞争。双孪生系统在大多数晶粒内先后被激活,孪生和滑移机制相互交割,起到动态细化晶粒的作用,使强度显著提高。在变形后期,试验钢的变形机制主要是TRIP效应,以及孪生与滑移的相互作用而诱发了去孪生机制,层状组织出现,孪晶特征减弱,从而导致样品的局部变形和失效。     

Strain Hardening Behavior of High Performance FBDP,TRIP and TWIP Steels

Based on n‐value differential equation and microstructural observation, strain hardening behaviors of FBDP, TRIP, and TWIP steels during uniaxial tension were investigated. TRIP steel exhibits both superior strength and ductility than FBDP steel, and TWIP steel displays much higher total and uniform elongations in comparison to FBDP and TRIP steels. The instantaneous n values of FBDP and TRIP steels increase at small strains, reach a maximum value, smoothly decrease at higher strains, and then rapidly drop up to the specimen rupture. The strain hardening of TRIP steel persists at higher strains where that of FBDP steel begins to diminish. TWIP steel exhibits gradually increased instantaneous n values over the whole uniform plastic deformation, implying that TWIP steel shows a much larger strain hardening capability than FBDP and TRIP steels.     

碳含量对新型Fe-Ni-Mn-Si-C系TWIP钢组织和力学性能的影响

通过光学显微镜、X射线衍射和透射电镜等方法研究了碳含量对Fe-Ni-Mn-Si-C系合金微观组织和力学性能的影响。结果表明:Fe-Ni-Mn-Si-C系合金的主要塑性变形机制为孪生诱发塑性(TWIP)效应。碳的质量分数由0.70%增加至0.98%,合金的屈服强度和抗拉强度分别由391 MPa和860 MPa增大到458 MPa和974 MPa,伸长率由63.6%提高到69.2%。随着碳含量的提高,Fe-Ni-Mn-Si-C系合金出现明显的动态应变时效现象。Fe-15Ni-12Mn-2.5Si-XC合金具有良好的应变硬化能力,随着碳的质量分数提高至0.98%,最大应变硬化指数达到0.73。     

Effects of High Strain Rate on Properties and Microstructure Evolution of TWIP Steel Subjected to Impact Loading

 The mechanical properties of the TWIP steel subjected to impact loading at various strain rates were analyzed by the Split Pressure Hopkinson Bar. Meanwhile the microstructure of the TWIP steel fore-and-after the dynamic deformation were characterized and analyzed by optical microscopy (OM), X-ray diffraction (XRD), and transmission electron microscope (TEM). The result shows that when the TWIP steel was deformed under dynamic station, the stress, microshardness and work hardening rate increase with the increment of strain and strain rate; there exist stress fluctuation and decline of work hardening rate for adiabatic temperature rising softening. There exist many pin-like deformation twins in the microstructure of the TWIP steel subjected to impact loading, the grain size after deformation is bigger than that before; the interaction of twins with dislocation and twins with twins, especial emergence of high order 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 raises, deformation twins unite together; furthermore, deformation twins become denser because the nucleation rating enhancing with strain rate increasing.     

Microstructure and Mechanical Properties of Hot-Rolled Fe-Mn-C-Si TWIP Steel

 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.     

1000MPa级DP钢的准静态拉伸行为与应变速率的关系

研究1000MPa的双相钢（DP钢）在室温下的准静态拉伸行为与应变速率（10^-2、10^-1、10^-1s^-1）的关系。结果表明,在准静态拉伸条件下,DP钢的拉伸性能是与应变速率相关的。随着应变速率提高,材料的屈服强度、抗拉强度、屈强比和加工硬化指数明显升高,而均匀伸长率、断裂伸长率略有下降;另外,应变速率对材料的...     

碳含量对Fe-Ni-Mn-Si-C系TWIP钢应变硬化行为的影响

采用单向拉伸、金相组织观察、TEM等方法,研究了3种不同碳含量Fe-Ni-Mn-Si-C系TWIP钢的拉伸应变硬化行为。研究结果表明,随着碳含量的增加,合金的强度和伸长率均提高,当碳质量分数为1.0%时,该TWIP钢具有较好的综合力学性能,强塑积达到83 160 MPa.%。3种TWIP钢的真应力-真应变曲线均不完全遵...     

Evaluation of Strain Hardening Parameters

The plane-strain compression test for three kinds of materials was carried out in atemperature range between room temperature and 400 ~C. The a- e curves and strain-hardeningrate at different temperatures were simulated and a reasonable fit to the experimental data wasobtained. A modified model created by data inference and computer simulation was developed todescribe the strain hardening at a large deformation, and the predicted strain hardening are in agood agreement with that observed in a large range of stress. The influences of different param-eters on strain hardening behaviour under large deformation were analysed. The temperatureincrease within the test temperatures for stainless steel 18/8 Ti results in dropping of flowstress and strain-hardening rate. For favourable r-fibre texture to obtain high r, the cold roll-ing was applied at large reduction. In the experimental procedure, the X-ray diffraction test wascarried out to compare the strain hardening and microstructure under large deformation for abcc steel (low carbon steel SS-1142). The results indicate that the high strain-hardening ratepossibly occurs when the primary slip plane {110} is parallel to the rolling plane and the strain-hardening rate decreases when lots of {110} plane rotate out from the orientation {110}//RP.     

高应变率下纯钛动态压缩力学性能各向异性

利用Instron电子拉伸机和分离式霍普金生（SHPB）压杠实验装置,研究了准静态和动态压缩条件下织构多晶纯钛板TA2的力学性能,对织构多晶纯钛板法向ND、轧向RD、横向TD等三个方向进行了压缩实验,得到了不同应变率下的应力-应变曲线。结果表明对于轧制和退火纯钛板,准静态和动态压缩力学性能均表现出明显的各向异性,且规律一致：均为ND方向屈服强度最大,TD次之,RD方向最小。     

Microstructure-Property Relationship of High Strength Low Alloy Steels During Tensile Testing at High Strain Rates

The influence of strain-rate on the room temperature mechanical properties of Dual-Phase and Transformation Induced Plasticity (TRIP) steels was investigated.The results showed that both plastic strain,and strength properties increased with increasing strain rates at high strain rates.At strain rates lower than approximateil 1s-1 the properties no longer have an advantageous proportionality to strain rate and remain strain rate neutral.Possible explanations are offered for trends exhibited,in terms of thermal and athermal considerations,in relation to the respective microstructures of the two steels.     

高强度高塑性TWIP钢的开发研究

通过调整成分,研究了一种新型的高锰钢成分对组织结构和TWIP效应以及对强度、塑性的影响。结果表明,该钢在变形后基体中存在大量细小的形变孪晶,室温下可具有相变诱导塑性和孪晶诱导塑性的TWIP效应,因而具有高的强度(1000MPa以上)和极高的伸长率(60％～90％)。该钢种是很有前途的高强度、高塑性钢种,满足下一代汽车制造对钢铁材料的需求。     

Static Tensile Deformation Behaviors of an Fe-30Mn-3Al-3Si TWIP Steel Studied by In-Situ Neutron Diffraction

TWIP (TWinning Induced Plasticity) steel is one of the advanced steels with attractive mechanical properties.The typical composition of TWIP steel includes a large amount of manganese with some aluminum and silicon.Previous study has shown that TWIP steel exhibits high strength with adequate elongation at high strain rates,so that TWIP steel is desired to be applied for automotive use.However,there are few studies concerning the deformation behaviors aimed to make clear the TWIP effect in TWIP steel.In this study,static tensile deformation behaviors of an Fe-30Mn-3Al-3Si TWIP steel and a SUS310S one were studied by in situ neutron diffraction during tensile deformation.In terms of mechanical properties obtained by the static tensile tests,the TWIP steel showed better balance of tensile strength and uniform elongation than the 310S steel.The angular dispersion neutron diffraction with a wavelength of 0.16 nm was performed during stepwise tensile testing by using a neutron diffractometer for residual stress analysis (RESA) at the Japan Atomic Energy Agency.A specimen was extended in a step by step manner and neutron diffraction profiles of (111),(200) and (311) for austenite were obtained at each step.The diffraction peak,lattice plane spacing,lattice plane strain and so on were determined by the profile analysis as a function of applied stress.The changes of lattice plane strain for austenite in the TWIP and 310S steels indicated several deformation stages in the tensile deformation and can be discussed the difference of intergranular stress between the two samples.     

Effect of the Deformation Twin Density on the Corrosion Behavior in TWIP Steel

Based on its excellent tensile strength-ductility property combination,twinning-induced plasticity (TWIP) steel shows great potential in applications for structural components in automobile industry.The aim of this research is to investigate the corrosion resistance properties and corrosion mechanism under room temperature in TWIP steel.The influence of the deformation twin density on corrosion property was primarily considered by salt spray test.The specimens used in the investigation are as-annealed and as-deformed respectively.The microstructure and corrosion resistance property were characterized by scanning electron microscope (SEM),optical microscope (OM) and so on.There are some annealing twins distributed randomly in austenitic grains in the as-annealed specimen.After the specimen was subjected to tensile experiment,the density of the deformation twins increased sharply,which are different from the annealing twins in size and morphology.It was found that the corrosion potential of the as-annealed is lower than that of the as-deformed and the corrosion current density behaves contrarily.After immersed in 5% NaCl solution salt spray for 48h,the as-deformed showed a bit better than the as-annealed in corrosion resistance.With the time prolonged,the gap between the two specimens in corrosion resistance increased rapidly.The corrosion morphologies varied in color and shape.Further investigation,carried out by SEM and EDS,indicated that as-annealed and the as-deformed followed pitting corrosion and uniform corrosion mechanism respectively.The reason for the difference in corrosion mechanism is possibly the presence of the deformation twins.The deformation twins formed during the tensile test refine grains by way of segmentation.The twin boundaries largely belong to the coincidence site lattice (CSL),which is on lower energy state.It suggests that the twins not only play a role in strengthening,but also improve effectively the corrosion resistance in TWIP steel.