高速冲击拉伸条件下TWIP钢的力学性能

采用气动式间接杆杆型冲击拉伸试验装置对5种不同成分的TWIP钢在10^2～10^3 s^-1应变速率范围内的动态拉伸变形行为进行了研究,并和静态拉伸性能作了比较。结果表明：随应变速率的提高,材料动态条件下的抗拉强度、断裂延伸率和能量吸收值均显著增加,均匀延伸率略有提高。TWIP钢在形变过程中产生形变孪晶显著改善了材料的塑性,因此在高应变速率下的延伸率仍较好。     

高速冲击拉伸条件下TWIP钢的力学性能

采用气动式间接杆杆型冲击拉伸试验装置对5种不同成分的TWIP钢在102～103s-1应变速率范围内的动态拉伸变形行为进行了研究,并和静态拉伸性能作了比较.结果表明:随应变速率的提高,材料动态条件下的抗拉强度、断裂延伸率和能量吸收值均显著增加,均匀延伸率略有提高.TWIP钢在形变过程中产生形变孪晶显著改善了材料的塑性,因此在高应变速率下的延伸率仍较好.     

TRIP780高强度钢板动态力学特性的研究

通过准静态和动态拉伸实验,获得了材料的力学性能参数,分析了TRIP780高强度钢板材的力学性能特点。基于Johnson-Cook模型建立了描述TRIP780高强度钢应变率相关性的本构关系模型,并将由该模型模拟得到的动态拉伸结果同实验结果进行对比,对比结果表明,数值模拟的结果与实验结果具有较好的一致性。利用数值模拟技术,分别模拟TRIP780钢和普通IF钢的薄壁梁冲击压溃过程,结果表明,TRIP780具有较好的抗冲击碰撞性能。     

评测车用钢动态变形吸能特性的试验方法

文章研究了一种基于摆锤式仪器化冲击试验机所开发的,针对汽车用钢板实施中等应变速率冲击拉伸加载的试验方法,并以此获得了DC04、DC56、H220、TRIP700和DP780的动态响应特性与加载应力-应变关系。研究表明,以铁素体软钢为典型的速率敏感材料,随着其应变速率的提高,材料强度增加,而塑性受到抑制。TRIP钢的性能与加载速率无明显相关特性,其力学性能在静态与动态条件下相对稳定。DP780钢的强度与塑性在动态加载条件下得到同步提升。此外,通过将冲击拉伸破断能转化为应力与应变的积分,试验获得的E10%与Euniform及Et能量指标,可定量分析汽车用钢碰撞时变形与吸能的相关特性,成为评价车用钢减重与安全的纽带。试验表明,随着材料强度级别的提升,其动态吸能特性得以成比例升高。同时,由E10%与Euniform指标构成的能量安全裕度,揭示出TRIP钢具有最为优异的动态变形吸能潜质。     

高速冲击拉伸条件下低硅TRIP钢的延伸率特性

对低硅HSLA -TRIP钢在室温条件下 5 0 0s-1～ 1 70 0S-1应变率范围内的动态拉伸性能进行了研究。实验结果表明 ,随应变率增大 ,钢的均匀延伸率 (eu)下降、总延伸率(et)和能量吸收值增加 ,但强度 (σb)保持不变或略有提高 ,能量吸收的增幅随应变率增大而变缓。分析认为 :残余奥氏体在颈缩发生前的较完全转变有利于提高均匀延伸率 ;高应变率下能量吸收值的提高可能由两个原因造成 :一是大应变下的奥氏体相变推迟断裂的发生 ;二是动态拉伸中的绝热温升有利于总延伸率的提高。     

激光冲击强化对太阳能热发电用渗铝钢显微组织和高温拉伸性能的影响

目的研究激光冲击强化前后,渗铝321不锈钢的显微组织变化和高温拉伸行为。方法采用固体粉末包埋渗铝法对321奥氏体不锈钢板材拉伸试样进行渗铝处理,制成渗铝钢,再对渗铝钢中间8 mm?25 mm标距段进行双面激光冲击强化处理,激光波长为1064 nm,单脉冲能量为7 J,脉宽为20 ns,冲击次数为1次和3次,圆光斑直径为2.6～3 mm,搭接率50%,黑胶布为保护层,水为约束层,并评价激光冲击前后渗铝钢表面完整性。对渗铝钢在620下进行高温拉伸试验,获得真应力-真应变曲线、屈服强度、抗拉强度以及断后延伸率,并在扫描电镜下观察拉伸断口微观形貌。结果渗铝钢的表面粗糙度和显微硬度随着激光功率密度和冲击次数的增加而提高。激光冲击强化后的渗铝钢表现出更高的屈服强度、抗拉强度和断后延伸率,其中,以6.59 GW/cm2激光密度三次冲击的渗铝钢的高温拉伸性能最佳。激光冲击强化后的渗铝钢高温拉伸断口表现出韧性断裂特征。结论激光冲击强化后,渗铝钢表面发生明显塑性变形,形成了起伏较大的凹坑和凸台,改变了材料粗糙度。表面晶粒细化、位错运动加剧以及位错增殖使得材料表面硬度和激光冲击硬化影响层深度提高;另外,引入的高幅残余压应力的释放能够抵消外加拉应力,延缓表面裂纹的形核和扩展。激光冲击强化显著改善了渗铝钢力学性能。     

温度对TRIP钢静、动态拉伸性能的影响

简要回顾了20世纪90年代至今，温度影响下TRIP钢静态拉伸性能研究和发展的状况。对造成性能差异的几种因素做了分析和比较。并介绍了温度影响下低Si—TRIP钢动态拉伸性能的进展。试验结果显示：在50℃-80℃温度下低Si--TRIP钢可以获得较好的强塑性配合。     

铁素体马氏体双相钢动态加载下的应变硬化行为

利用拉伸Split Hopkinson bar实验装置,对双相钢进行不同应变率下的动态拉伸实验,并应用Johnson-Cook本构模型,对双相钢的动态拉伸性能及应变硬化行为进行分析。结果表明,双相钢具有明显的应变率敏感性;与静态加载类似,在动态加载条件下,双相钢具有较高的初始应变硬化率,随着应变的增加,应变硬化率先迅速下降,而后趋于平缓。     

全层状TiAl合金室温拉伸性能的影响因素

研究了显微组织和应变速率对全层状Ti-47Al-2Cr(at%)合金室温拉伸性能的影响，结果表明，全层状TiAl基合金的室温拉伸强度和室温延伸率随晶团尺寸和层片间距的减小而提高；其室温拉伸强度随应变速率的加快而提高；而应变速率对其室温延伸率的影响与显微组织相关，低延性全层状TiAl基合金的室温延伸率对应变速率不敏感，而高延性全层状TiAl基合金的室温延伸率对应变速率敏感，并随应变速率的加快而提高。     

应变速率对低C高Mn TRIP/TWIP钢组织演变和力学行为的影响

研究了Fe-18Mn低C高Mn TRIP/TWIP钢在应变速率范围为1.67×10^-4-10³s^-1的室温拉伸实验过程中力学性能和组织的变化.在准静态拉伸应变速率范围内(1.67×10^-4-1.67×10^-1s^-1),应变速率对高Mn TRIP/TWIP钢的抗拉强度产生逆效应,随着应变速率的加快,抗拉强度和延伸率都降低;而在动态拉伸应变速率范围内(10¹-10³s^-1),应变速率对高Mn TRIP/TWIP钢的延伸率产生逆效应,抗拉强度和延伸率都随着应变速率的加快而增加;在应变速率为10³s^-1时,高Mn TRIP/TWIP钢抗拉强度可达到957 MPa,延伸率达到55.8%,具有较好的综合力学性能;随着应变速率的提高,马氏体转变量减少,孪生变形向多个方向发展.采用SEM,TEM和XRD等方法对变形前后的组织进行了分析,在所有应变速率范围内的拉伸变形过程中都产生了奥氏体向马氏体转变和形变孪晶,并且在应变速率为10³s^-1的高速拉伸过程中产生绝热温升效应,使得基体软化.     

ON THE TENSILE MECHANICAL PROPERTY OF Si-Mn TRIP STEELS AT HIGH STRAIN RATE

二．互ntYO*llCtloliAs kn OWOWn,the beh yyiors of the strength and ductility of material under dynamic con－dltlon are obviously differs尬from those under static condition．几ensure the reft劝ility ofstructure under dynamic or impact loading It Is necessar     

Effect of strain rate on deformation behavior of TRIP steels

Tensile deformation behavior of Si–Mn TRIP (TRansformation Induced Plasticity) steel with vanadium and without vanadium and the DP (Dual Phase) steel of the same composition were studied in a large range of strain rate (0.001–2000 s^?1) by routine material testing machine, rotation disk bar–bar tensile impact apparatus and high-speed material testing machine of servo-hydraulic type. In situ measurement of the transformation of retained austenite was performed by means of X-ray stress apparatus in order to have detailed knowledge about the transformation of retained austenite at quasi-static tensile. Microstructure of steels before and after tensile were observed by means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). It is shown that there is no yield plateau observed on the stress–strain curve at quasi-static condition for TRIP steel containing vanadium because the vanadium carbide suppress the formation of Cottrell atmosphere in matrix. Retained austenite of Si–Mn TRIP steel containing vanadium transforms to martensite at loading stress of 502 MPa (its yielding strength is 486 MPa), while the transformation of retained austenite in matrix of Si–Mn TRIP steel without vanadium happens when its yielding process is finished at quasi-static tensile. It is confirmed that phase transformation of retained austenite in TRIP steel is strain induced phase transformation. It is noted that tensile elongation of TRIP steel at dynamic tensile is always lower than that at quasi-static tensile. That is because gradually strain induced phase transformation of retained austenite in TRIP steel is suppressed by deformation localization at dynamic tensile.     

The effect of silicon, aluminium and phosphor on the dynamic behavior and phenomenological modelling of multiphase TRIP steels

Multiphase TRansformation Induced Plasticity (TRIP) steels combine excellent ductility and high strength, making them ideally suited for shock absorbing parts in the automotive industry. When designing structures for impact, an understanding of the mechanical properties of materials under high strain rate conditions is essential. An extensive experimental program using a split Hopkinson tensile bar set-up was established in an effort to investigate the dynamic properties of various TRIP steel grades. Four different TRIP steels are described with varying contents of the alloying elements silicon, aluminium and phosphor. Moreover, several phenomenological models describing the strain rate and temperature-dependent mechanical behaviour are validated. TRIP steel grades in which aluminium is the main alloying element show high elongation values, whereas a high silicon content results in an increase in strength. The widely used Johnson-Cook model can describe the behaviour of TRIP steels and provides the opportunity to study its material and structural response.     

高锰TRIP/TWIP效应共生钢高速变形过程中的组织演变及变形行为

对18Mn-3Al-3Si和21Mn-3Al-3Si高锰TRIP/TWIP效应共生钢动态变形过程中的变形行为,应变硬化速率、真应力和应变硬化指数随真应变的变化,以及应变硬化和基体软化间的相互作用等进行了研究,采用OM,SEM,TEM和XRD等方法对变形前后的组织进行了分析.结果表明,高应变速率下,TRIP/TWIP效应共生钢应变诱发相变途径为γ→ε→α;高速变形对滑移的抑制、奥氏体向马氏体的相变和形变孪晶对奥氏体晶粒的细化是应变硬化的主要因素;造成基体软化的原因是绝热温升效应、ε→γ的逆相变和孪晶的动态再结晶.     

The high-speed deformation behavior of TRIP steels

The high-speed deformation behavior of TRIP steel was investigated at strain rates ranging from 10⁻² s⁻¹ to 10³ s⁻¹. The effects of metallurgical factors, such as the rolling direction, thickness, and gage length, on the tensile properties at various strain rates were evaluated. The ultimate tensile strength, uniform elongation, strain rate sensitivity, absorbed energy, and strain-hardening exponent are reported. In general, the strength increases and the ductility decreases as the strain rate increases. The samples with a high amount of retained austenite had two distinct regions of strain rate sensitivity, showing high strain rate sensitivity over a strain rate of 10² s⁻¹. The tensile properties were not affected by the gage length and thickness of the tensile samples; however, the rolling direction of the tensile samples affected the UTS values slightly. The absorbed energy of the TRIP steel greatly exceeded that of HSLA steel.     

EFFECTS OF TEST TEMPERATURE AND STRAIN RATE ON THE MECHANICAL PROPERTIES IN AN INTERCRITICALLY HEAT-TREATED BAINITE-TRANSFORMED STEEL

1.IntroductionThe demand for high strength steels with excellent ductility has increased in the automotive indus-try in order to improve manufacturing and safety and to reduce weight. High strength transforma-tion-induced plasticity (TRIP) steel sheets have received increased attention, as they have both high strength and ductility due to the martensitic transformation of retained austenite during plastic defor-mation.Transformation-induced plasticity was the phenomenon first found in steel …     

High-rate tensile properties of Si-reduced TRIP sheet steels

There have been efforts to develop Si-reduced TRIP steels to improve the wettability of Zn coatings, since the conventional CMnSi-TRIP steels suffer from poor galvanizability. In addition, for the development of potential applications of Si-reduced TRIP steels in vehicle crash management, a better understanding of high strain rate properties is required. In the present study, the effects of alloying elements, such as Cu, Al, Si, and P, on the high-rate tensile properties of Si-reduced TRIP sheet steels were investigated. Tensile tests were performed with a servo-hydraulic tensile testing machine at strain rates ranging from 10⁻² to 6 × 10² s⁻¹, and the ultimate tensile strength, elongation, strain rate sensitivity, and absorbed energy were evaluated. The retained austenite volume fractions and carbon content of the specimens were measured using neutron diffraction. The UTS was increased with Cu, Al, Si, and P alloying throughout the strain rate range, and the alloying effect on UTS was considerable with Cu and P. The effects of alloying on the microstructure were not significant. All the steels tested in this study exhibited positive strain rate sensitivity, and the m value at strain rates higher than 10 s⁻¹ was at least two times higher than that at lower strain rates.     

2195铝锂合金板材高速拉伸力学特性和变形机理研究

为探究新淬火态2195铝锂合金高应变速率拉伸的力学性能和变形机理,采用分离式Hopkinson拉杆装置进行高应变速率拉伸实验,应变速率范围为1000 s-1~4500 s-1,并通过EBSD技术分析不同应变速率拉伸下合金的织构类型和微观组织演变规律。结果表明：随应变速率的增大,合金的强度和延伸率同步上升。当应变速率达到4200 s-1时,抗拉强度和延伸率分别达到398 MPa和63%,相比较于准静态拉伸,延伸率显著提高。由EBSD结果分析可知,随应变速率的增大,小角度晶界占比上升、KAM均值增大,Goss织构和S织构强度和体积分数上升。同时发现高应变速率拉伸下不仅软取向晶粒的塑性变形更加充分,而且可以启动更多的硬取向晶粒协调变形,进而揭示了高应变速率拉伸下的变形机理。