Nb含量对Fe-22Mn-0.4C合金层错能和力学性能的影响

研究了微合金元素Nb对Fe-22Mn-0.4C合金层错能和力学性能的影响,利用X射线峰位移法测量计算了不同Nb含量的Fe-22Mn-0.4C合金的层错几率变化.结果表明随着Nb含量的提高,合金的层错几率降低,层错能提高.同时,Fe-22Mn-0.4C合金在拉伸变形过程中,变形机制由以TRIP效应为主导机制变为以TWIP效应为主导机制.不同的变形机制使不同Nb含量合金的力学性能发生变化,并使变形后的层错几率出现不同的变化量.     

铝、铜、铬合金元素对Fe 21Mn 04C TWIP/TRIP钢层错能和力学性能的影响

  参考文献建立了Fe Mn C合金层错能的热力学模型,用模型计算了铝、铜、铬元素对Fe 21Mn 04C合金层错能的影响规律;在Fe 21Mn 04C合金中添加合金元素,研究其对层错能的影响。研究结果表明：铝和铜增加合金的层错能,而铬则降低合金的层错能;当层错能低于107mJ/m2时,Fe 21Mn 04C合金相组成为γ+ε,当层错能为10~1902mJ/m2时,合金的相组成为γ+ε+a,当层错能高于1902mJ/m2时,合金的相组成为单相的γ;层错能的变化和添加了合金元素铝、铜、铬的Fe 21Mn 04C合金性能变化没有相一致的关系,说明影响Fe 21Mn 04C合金力学性能的因素很多,需要进一步的研究。     

Fe-20Mn-0.6C TWIP钢力学性能和微观组织的演变

 研究一种Fe-Mn-C系新型TWIP钢的力学性能和微观变形机制。采用静态拉伸方法测试Fe-20Mn-0.6C钢在热轧和冷轧及热处理后的力学性能,通过金相、X-射线衍射、透射电镜观察等方法研究该钢的微观组织演变。结果表明：试验钢经过热轧后,表现出优异的综合力学性能,伸长率高达100%,抗拉强度达到924MPa。将热轧钢板经过适量冷轧后其抗拉强度提高到1210MPa。 热轧态组织为等轴的奥氏体基体及退火孪晶,拉伸变形后其微观组织中孪晶密度显著增加,晶粒内由一套孪晶系逐渐演化为两套孪晶系,而且因变形诱导马氏体相变产生大量马氏体组织。     

低温奥氏体钢的层错能

根据层错及层错能的物理本质和测试层错的依据，明确了层错能和层错形核能的定义。借助计算机处理大量试验结果得到了计算机层错能的表达式。     

铜含量对高碳TWIP钢组织和力学性能的影响

 采用真空熔炼法制备了Fe-20Mn-XCu-1.3C系高强度高塑性合金钢。通过单向拉伸试验和OM观察,研究了铜含量的变化对该合金微观组织和力学性能的影响。结果表明：Fe-20Mn-XCu-1.3C系合金拉伸变形前后均为单相奥氏体组织。随着铜含量的增加,合金的屈服强度和伸长率提高,而抗拉强度降低,Fe-20Mn-3.0Cu-1.3C合金的抗拉强度为1256MPa,伸长率为77.6%,强塑积达到97465.6MPa·%,具有优异的综合力学性能。铜含量的增加提高合金的层错能,推迟了变形过程中孪晶的形成并降低了孪晶的形成速率,使位错滑移更容易发生。Fe-20Mn-XCu-1.2C系合金具有较高的加工硬化速率水平,其加工硬化速率随着铜含量的增加而降低。     

高锰TWIP钢层错能的研究进展

高锰TWIP钢的高强度、高塑性和高能量吸收能力与其堆垛层错能有关。TWIP效应对应的层错能上、下限值仍未统一,尤其是TWIP向MBIP(微带诱导塑性)转变的临界判据仍有待于深入分析。XRD、TEM和EAM是测定奥氏体层错能最常用的实验方法。同一TWIP钢的层错能及其变化规律存在实验方法的相关性。正规和亚正规溶液模型、Bragg-Williams模型和双亚点阵模型是计算高锰钢层错能的常见模型。对同一TWIP钢来说,不同模型的预测值并不相同,且与实测值也存在差异。铃木效应引起层错能随间隙原子浓度非线性变化,这在计算时是不能忽略的。规范实验方法、提高设备精度和完善热力学模型及其数据库有助于获得准确可靠的层错能值。     

微合金元素B对轻质TWIP钢组织及力学性能的影响

摘要：将质量分数为0.002%的微合金元素B加入至Fe-28Mn-9Al轻质TWIP钢中,以期改善其强塑积及室温冲击性能。利用X射线衍射、扫描电镜、电子万能拉伸试验机和金属摆锤冲击试验机对热轧TWIP钢的物相组成、微观组织、力学拉伸性能及室温冲击韧性进行了研究与分析。结果表明,微合金元素B的添加具有延缓奥氏体向铁素体转变的作用,细化了奥氏体晶粒,提升了钢的力学性能,TWIP钢的塑性、强塑积和冲击韧性均有明显的提高。     

高锰TRIP/TWIP钢变形行为的研究进展

高强度高塑性是汽车用钢发展的主要趋势.Fe-Mn-Al-Si系TRIP/TWIP钢、Fe-Mn-C系TWIP钢和Fe-Mn-Al-C钢具有高的强度、优良的塑性和成形性,为新一代汽车材料.近年来,这些奥氏体汽车用钢的研究与开发受到了高度重视.本文对高锰TRIP/TWIP钢的组织性能、晶体学行为、强韧化机制、应变硬化行为和高速变形方面的研究工作进行了综述.     

TWIP不锈钢层错能计算、塑韧性和耐蚀性能研究

添加Cr元素设计具有形变诱导孪生效应(twinning-induced plasticity,TWIP)的高强不锈钢,采用亚点阵晶格模型运用Matlab计算得到设计合金层错能(stacking fault energy,SFE)为37.65 mJ/m2.通过(900～1 200)℃×1 h热处理发现晶粒尺寸、退火孪晶数...     

W、Co对Ni合金层错能影响的热力学计算

运用置换原子计算层错能的热力学模型,计算了Ni-W、Ni-Co合金的层错能.结果表明:随温度升高合金的层错能提高.随着W、Co含量的提高,Ni-W、Ni-Co合金的层错能提高;随W、Co质量分数的增多,Ni合金层错能先增加后减小,存在极大值,但W使Ni合金层错能增加的幅度较小.     

Effect of Carbon Content on Stacking Fault Energy of Fe-20Mn-3Cu TWIP Steel

The influence of carbon content on the stacking fault energy(SFE)of Fe-20Mn-3Cu twinning-induced plasticity(TWIP)steel was investigated by means of X-ray diffraction peak-shift method and thermodynamic modeling.The experimental result indicated that the stacking fault probability decreases with increasing carbon addition, the SFE increases linearly when the carbon content in mass percent is between 0.23% and 1.41%.The thermodynamic calculation results showed that the SFE varied from 22.40to 29.64mJ·m-2 when the carbon content in mass percent changes from 0.23%to 1.41%.The XRD analysis revealed that all steels were fully austenitic before and after deformation,which suggested that TWIP effect is the predominant mechanism during the tensile deformation process of Fe-20Mn-3Cu-XC steels.     

热轧高锰TRIP/TWIP钢组织性能研究

利用控轧控冷工艺开发了锰质量分数为18.8%的热轧高锰TRIP/TWIP钢板,分析了轧制工艺参数对热轧高锰钢组织和性能的影响,讨论了实验钢的断裂机理。结果表明：通过控轧控冷方法可以热轧出抗拉强度达到940 MPa左右,断裂伸长率在40%以上的高锰钢板。冷却速度和卷取温度等工艺参数对实验钢组织性能影响不是非常明显。高锰钢优异的力学性能是TRIP和TWIP效应共同作用的结果。高锰钢拉伸呈韧性断裂,裂纹多沿奥氏体/马氏体晶界萌生、扩展。     

高锰奥氏体TRIP/TWIP钢的组织和力学性能

研究了两种不同锰含量的高锰奥氏体钢在室温拉伸变形过程中力学性能和组织的变化.结果表明,随着钢中锰含量的变化,实验钢在流变应力的作用下出现相变诱导塑性的TRIP效应和孪晶诱导塑性的TWIP效应.在1×10-3 s-1的初始应变速率条件下,锰的质量分数为23.8%的实验钢可达到666 MPa的抗拉强度和67%的伸长率,而锰的质量分数为33%的实验钢可达到540 MPa的抗拉强度和97%的伸长率.并且在10-3～10-1 s-1的初始应变速率范围内,实验钢的抗拉强度对于流变应力不敏感,而实验钢的塑性则表现出一定的应变速率敏感性.由于该钢具有较好的综合力学性能,有望作为新一代高强度、高塑性汽车用钢.     

Fe-22Mn-0.7CTWIP钢的热塑性与断裂机制

基于Gleeble-1500热力模拟试验机测定了Fe-22Mn-0.7C TWIP钢和Q235钢700~1300℃范围内的静态拉伸行为.采用光学显微镜、扫描电子显微镜、能谱仪、电子探针微区分析等技术表征两钢种不同温度下的变形特征和断口形貌.通过分析基体化学成分、相体积分数、晶粒尺寸、凝固缺陷等因素探讨TWIP钢铸态热塑性的变化规律及其影响机制.研究结果表明,Fe-22Mn-0.7C TWIP钢700~1250℃范围内的铸态抗拉强度高于Q235,而其断面收缩率低于40%,且断口均以沿枝晶间断裂方式为主.晶粒细化和控制溶质显微偏析有利于提高TWIP钢热塑性,与基体均质性改善有关.此外,增加应变速率TWIP钢拉伸强度和断面收缩率同时增大.     

Microstructures and Mechanical Properties of Fe-Mn-（Al, Si） TRIP/TWIP Steels

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.     

Study on Microstructures and Mechanical Properties of High Manganese Steels with TRIP/TWIP Effects

In the present work, advanced high strength and high ductility TRIP/TWIP steels with different manganese concentrations were studied. The microstructures of these steels were evaluated prior to and after deformation and the mechanical properties of these steels were determined. The microstructure analysis indicated that both TRIP and TWIP effects appeared in the steel with lower Mn content, while the TWIP effect was the dominant deformation mechanism in the steel with a higher Mn content, with many deformation twins formed during the deformation. In addition, the forming limit diagrams of these steels were recorded and the results showed an excellent formability.     

Microstructure and Mechanical Properties of TWIP Steel Joints

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.     

On the Relation of Microstructure and Texture Evolution in an Austenitic Fe-28Mn-0.28C TWIP Steel During Cold Rolling

In the present study, microstructure and texture evolution in an austenitic Fe-28 wt pct Mn-0.28 wt pct C TWIP steel in the range between 10 and 80 pct reduction by cold rolling were systematically analyzed. The formation of the observed microstructural features occurred in three different stages: I (10 to 20 pct)—mainly slip lines, grain elongation, and formation of few twin-matrix lamellae; II (30 to 50 pct)—severe increase of the volume fraction of twins, alignment of twins with the rolling plane, and formation of microshear bands; and III (60 to 80 pct)—further alignment of twins, evolution of a herring bone structure, and macroshear bands. In contrast to most f.c.c. metals, the transition from Copper- to Brass-type texture occurred at low strain levels (30 pct). This behavior is attributed to the early formation of deformation twins in the material and can be related to the SFE of this high manganese steel. At higher reduction levels, microscopic (≥40 pct) and macroscopic shear band formation (≥60 pct) contributed to the increase of randomly oriented grains, mainly at the expense of the Brass component. Furthermore, the formation of the Goss component and of the 〈111〉//ND fiber (γ) is attributed to severe twin formation.