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1.
Abstract: Microstructure evolution and mechanical properties of newly designed 01C-6Mn-05Si-1Al TRIP-aided steels under different annealing conditions and the effects of matrix microstructure before intercritical annealing on the final microstructure were studied by means of X-ray diffraction (XRD), scanning electron microcopy (SEM), dilatometric simulation, optical microstructure (OM) and tensile testing in this work. The experimental results indicate that the TRIP steel with Mn of 6% could form a considerable amount of retained austenite with good TRIP effect after a simple intercritical annealing treatment, and the matrix microstructure before intercritical annealing treatment can greatly affect the final microstructure. The original microstructure of the ferritic matrix steel was eliminated, while annealed martensite was remained from the martensite matrix steel under the same intercritical annealing conditions. 相似文献
2.
Mechanical properties and microstructure in high strength hot dip galvanizing TRIP steel were investigated by optical microscope (OM), transmission electron microscope (TEM), X-ray diffraction (XRD), dilatometry and mechanical testing. On the heat treatment process of different intercritical annealing (IA) temperatures, isothermal bainitic transformation (IBT) temperatures and IBT time, this steel shows excellent mechanical properties with tensile strength over 780 MPa and elongation more than 22%. IBT time is a crucial factor in determining the mechanical properties as it confirms the bainite transformation process, as well as the microstructure of the steel. The microstructure of the hot dip galvanizing TRIP steel consisted of ferrite, bainite, retained austenite and martensite during the short IBT time. The contents of ferrite, bainite, retained austenite and martensite with different IBT time were calculated. The results showed that when IBT time increased from 20 to 60 s, the volume of bainite increased from 14.31% to 16.95% and the volume of retained austenite increased from 13.64% to 16.28%; meanwhile, the volume of martensite decreased from 7.18% to 1.89%. Both the transformation induced plasticity of retained austenite and the hardening of martensite are effective, especially, the latter plays a dominant role in the steel containing 7.18% martensite which shows similar strength characteristics as dual-phase steel, but a better elongation. When martensite volume decreases to 1.89%, the steel shows typical mechanical properties of TRIP, as so small amount of martensite has no obvious effect on the mechanical properties. 相似文献
3.
Influence of Tempering Process on Mechanical Properties of 00Cr13Ni4Mo Supermartensitic Stainless Steel 总被引:6,自引:0,他引:6
To investigate the influence of tempering process on microstructural evolutions and mechanical properties of 00Cr13Ni4Mo supermartensitic stainless steel(SMSS),specimens were tempered in the temperature range of 520-720 ℃ for 3 h followed by air cooling and an optimized tempering temperature was chosen to prolong holding time from 3 to 12 h.After heat treatments,microstructure examination was conducted by scanning electron microscope,X-ray diffraction examinations,hardness measurements and tensile tests.The results revealed that the superior mechanical properties were achieved by quenching at 1040 ℃ for 1 h+water cooling and tempering at 600 ℃ for 3 h+air cooling.Increasing isothermal tempering time could improve the toughness notably.It was believed that the property was correlated with the microstructure of tempered lath martensite and retained austenite.More retained austenite content is beneficial to the higher toughness of the SMSS. 相似文献
4.
《钢铁研究学报(英文版)》2015,(11)
The effect of subcritical annealing temperature on microstructure and mechanical properties of SCM435 steel was investigated through changing the heating and soaking temperature as 660 °C, 680 °C, 700 °C, 720 °C and 745 °C. The microstructure and mechanical properties of intercritically annealed specimens were analyzed. With increasing the subcritical annealing temperature from 660 °C to 720 °C, the spheroidization ratio gradually increased, and the mechanical properties, formability and Vickers hardness were improved. According to the comprehensive comparison of mechanical properties and formability, the subcritical process at soaking temperature of 680-720 °C could achieve similar annealing effect as that of intercritical process. Therefore, the subcritical annealing temperature could be set as 700 °C in practice, with the Ac1 temperature fluctuation within ±20 °C, and the applicability and stability of subcritical annealing were guaranteed in industrial application. The plant results of the cold heading showed that the subcritical annealing could replace original intercritical annealing successfully with significantly saving time and energy. 相似文献
5.
The microstructural evolution and mechanical property of 00Cr13Ni5Mo2supermartensitic stainless steel(SMSS)subjected to different heat treatments were investigated.Room tensile tests,hardness tests,scanning electron microscopy,transmission electron microscopy and X-ray diffraction were conducted on the heat-treated steels.It is found that the microstructure of the heat-treated steel is composed of tempered lath martensite,retained austenite andδ-ferrite.The austenitizing temperature and tempering temperature have a significant effect on the microstructural changes,which leads to the complex variations of mechanical properties.The fine tempered lath martensite and more dispersed reversed austenite in the microstructure facilitate improving the comprehensive mechanical properties of the studied steel.The optimal heat treatment process of 00Cr13Ni5Mo2SMSS is obtained by austenitizing at 1 000℃for 0.5h+air cooling followed by tempering at 630℃for 2h+air cooling,where the excellent combination of tensile strength,elongation and hardness can be achieved. 相似文献
6.
The controlled cooling technology following hot rolling process is a vital factor that affects the final microstructure and mechanical properties of the hot-rolled transformation induced plasticity (TRIP) steels. In the present study, low alloy C-Si-Mn TRIP steel was successfully fabricated by hot rolling process with a 450 hot rolling mill. To maximize the volume fraction and stability of retained austenite of the steel, two different cooling methods (air-cooling and ultra-fast cooling “AC-UFC” and ultra-fast cooling, air-cooling and ultra-fast cooling “UFC-AC-UFC”) were conducted. The effects of the cooling method on the microstructure of hot-rolled TRIP steel were investigated via optical microscope, transmission electron microscope and conversion electron Mssbauer spectroscope. The mechanical properties of the steel were also evaluated by conventional tensile test. The results indicated that ferrite and bainite in the microstructure were refined with the cooling method of UFC-AC-UFC. The morphology of retained austenite was also changed from small islands distributing in bainite district (obtained with AC-UFC) to granular shape locating at the triple junction of the ferrite grain boundaries (obtained with UFC-AC-UFC). As a result, the TRIP steel with a content of retained austenite of 1152%, total elongation of 32% and product of tensile strength and total elongation of 27552 MPa·% was obtained. 相似文献
7.
《钢铁研究学报(英文版)》2011,(Z1):200-207
Designing of alloy concept and process for DP,TRIP and TWIP steels stressing at martensite transformation are analyzed.For DP steel,austenite volume percent and its carbon content at different intercritical temperatures are calculated as well as the tensile strength of the steel,which meet well with the experimental result.The condition for dissolution of carbide is discussed by experiments and predicted by kinetic estimation.Several sample TRIP steels are prepared and their concentration profiles are calculated showing different diffusion characteristics of elements.Calculation also shows carbon enrichment is successful in this stage through the quick diffusion of carbon from ferrite to austenie.In order to maintain the austenite stability or to prevent precipitation of cementite,minimum cooling rate from the intercritical zone to over aging stage is obtained through kinetic simulation.Bainite transformation is estimated,which indicates the carbon rerichment from ferrite of bainite structure to austenite in this stage is also successful.Thermal HCP martensite transformation and the strain induced martensite transformation in TWIP steel is introduced.Relationship between transformation and mechanical properties in the steel is also mentioned. 相似文献
8.
《钢铁研究学报(英文版)》2017,(11)
The Fe-0.21 C-2.2 Mn-0.49 Si-1.77 Al transformation induced plasticity(TRIP)-aided steel was heat treated at various austenitizing temperatures under both TRIP-aided polygonal ferrite type(TPF)and annealed martensite matrix(TAM)processes.The microstructure evolution and their effects on mechanical properties were systematically investigated through the microstructure observation and dilatometric analysis.The microstructure homogeneity is improved in TPF steel heated at a high temperature due to the reduced banded martensite and the increased bainite.Compared with the mechanical properties of the TPF steels,the yield strength and elongation of the TAM steels are much higher,while the tensile strength is lower than that of TPF steels.The stability of intercritical austenite is affected by the heating temperature,and thus the following phase transformation influences the mechanical properties,such as the bainite transformation and the precipitation of polygonal ferrite.Obvious dynamic bainite transformation occurs at TAM850,TAM900 and TAM950.More proportion of polygonal ferrite is found in the sample heated at 950°C.The bainite transformation beginning at a higher temperature results in the wider bainitic ferrite laths.The more proportion of polygonal ferrite and wide bainitic ferrite laths commonly contribute to the lower strength and better elongation.The uniform microstructure with lath-like morphology and retained austenite with high average carbon content ensures a good mechanical property in TAM850 with the product of strength and elongation of about 28 GPa·%. 相似文献
9.
Influence of PreTransformed Martensite on WorkHardening Behavior of SUS 304 Metastable Austenitic Stainless Steel 总被引:2,自引:0,他引:2
The metastable austenite was transformed to martensite by prestrain tension of SUS304 stainless steel to study the influence of transformed martensite on its subsequent work hardening behavior under the uniaxial tensile condition. The X ray diffractometer (XRD) was employed to detect the transformed martensite. Results showed that the volume fraction of transformed martensite increases with increasing prestrain. The pre transformed martensite in the microstructure remarkably affects the deformation behavior of the steel, and the strength increases and the elongation decreases. The work hardening curve of prestrained specimens observably changes with true strain. The work hardening exponent n of stainless steel decreases with the increase of pre transformed martensite. The achievement is a significant contribution to the process design during pressing. 相似文献
10.
《钢铁研究学报(英文版)》2015,(7)
To develop super-high strength TRIP steel for automobile application with good combination of strength and plasticity,an ultra-high-strength TRIP steel 0.2%C-2.0%Si-1.8%Mn was investigated at different intercritical annealing temperatures and bainitic isothermal temperatures.Microstructures were observed by scanning electron microscopy,transmission electron microscopy,electron backscatter diffraction,and X-ray diffraction,and mechanical properties were tested under a uniaxial tensile testing machine.It shows that the best comprehensive mechanical properties were obtained for the experimental steel particularly annealed at 820 ℃ and austempered at 410 ℃.Yield strength of the tested steel mainly depends on ferrite,while the high strength of the tested steel is related to martensite which forms through blocky austenite transformation during cooling and subsequent tensile test attributed to the TRIP effect.Hence,it could be concluded that the grain size of the retained austenite and carbon content in retained austenite are the main reasons for high elongation of the tested steel. 相似文献
11.
两相区退火处理含铝中锰钢的组织和力学性能 总被引:1,自引:0,他引:1
为了研究两相区退火处理对冷轧含铝中锰钢(0.2C-0.6Si-5Mn-1.2Al)(质量分数,%)微观组织和力学性能的影响规律,利用SEM、XRD及单轴拉伸等试验方法表征了不同工艺状态后的微观组织及测试了拉伸性能。结果表明,冷轧试验钢在退火过程中组织发生奥氏体逆转变,在退火温度为670℃、退火时间为10min时可获得较佳的力学性能,即抗拉强度达到1276 MPa,总伸长率达到51.8%,强塑积高达66.1GPa·%。随着退火温度升高,残余奥氏体组织逐渐粗化且向马氏体组织转变,机械稳定性逐渐降低。残余奥氏体机械稳定性主要受残余奥氏体中碳质量分数及其晶粒尺寸的影响,而残余奥氏体中锰质量分数对其影响较小。 相似文献
12.
The transformation, microstructure and mechanical properties of the 0. 2C- 5Mn TRIP steel after intercritical annealing were investigated using dilatometer, scanning electronic microscopy (SEM), transmission electron microscopy(TEM), X- ray diffraction (XRD), and tensile testing machine. The phase transformation thermodynamics of the investigated steel after intercritical annealing was calculated by Factsage software and the characteristics of the transformation were discussed. The results show that the reversed austenite content increases with the increasing of the intercritical annealing temperature, the carbon content in reversed austenite firstly increases and then decreases, manganese content in reversed austenite decreases, which results in the decreasing of the thermal stability of reversed austenite. When the intercritical annealing temperature is 700??, an obvious martensitic transformation occurs during the cooling process. With the increasing of intercritical annealing temperature, cementite is gradually dissolved, but it cannot be completely dissolved due to the short transformation time. When the intercritical annealing temperature is 600-675??, the microstructure after intercritical annealing consists of ferrite, cementite and retained austenite. When the intercritical annealing temperature is 700??, the microstructure after intercritical annealing consists of ferrite, retained austenite, martensite and a small amount of undissolved cementite. The engineering stress and strain curves of the investigated steel are significantly changed with increasing intercritical annealing temperature. At the same time, the optimal mechanical properties with tensile strength of 1138MPa and total elongation of 23% can be obtained after annealed at 675?? for 3min. 相似文献
13.
Sajad Ghaemifar 《Canadian Metallurgical Quarterly》2017,56(4):459-463
The effect of repetitive intercritical annealing on the mechanical properties and work-hardening response of a typical C–Mn dual-phase (DP) steel was studied by consideration of different pre-intercritical annealing microstructures and martensite volume fractions. It was revealed that the DP steels produced from the initial martensitic microstructure have much better mechanical properties compared with those originated from the ferritic–pearlitic banded microstructure. The repetitive intercritical annealing of the initial martensitic microstructure was effective for the enhancement of strength–ductility balance, where at a comparable ductility; a twofold increase in the tensile strength was obtained. Finally, these results were discussed based on the Crussard–Jaoul work-hardening rate analysis. 相似文献
14.
ZHAO Xiao- li ZHANG Yong- jian HUANG Hai- tao HUI Wei- jun WANG Cun- yu DONG Han 《钢铁研究学报》2018,30(8):642-649
Effect of warm- rolling and subsequent intercritical annealing time at 650?? on microstructure and mechanical properties of a medium- Mn steel 0. 1C- 5Mn was investigated by using uniaxial tensile testing, transmission electron microscopy (TEM) and X- ray diffraction (XRD) analysis. The results show that a duplex microstructure having both equiaxed and lamellar morphologies of reverted austenite and ferrite is obtained after intercritical annealing of the warm- rolled steel sheet. The amount of reverted austenite and its size increase with increasing annealing time, which causes a decrease of the mechanical stability of austenite and thus an increase of ultimate tensile strength (UTS) while a decrease of yield strength, total elongation (TEL) and the product of UTS to TEL (UTS??TEL). An excellent combination of strength and ductility of 40GPa??% could be obtained after a short time annealing of 5min. The combination of strength and ductility (UTS??TEL) could be increased by about 20% for the warm- rolled steel sheet compared to that of the cold- rolled steel sheet. It is thus proposed that warm- rolling is a promising way to simplify the traditional multi- stage rolling and annealing processes of medium- Mn steels as well as further enhancing it mechanical properties. 相似文献
15.
摘要:对中碳钢采用Q&P(淬火 碳分配)和I&QP(临界热处理,淬火 碳分配)热处理工艺,通过对试样的显微组织,残余奥氏体的体积分数及其碳含量,硬度及其拉伸性能进行分析,研究了临界加热对中碳Q&P钢组织和性能的影响。实验结果表明,经临界热处理的Q&P钢组织中,除了马氏体和残余奥氏体,还存在部分铁素体,同时残余奥氏体的体积分数较少,马氏体板条更加细小。在相同的碳分配时间下,I&QP试样的硬度和抗拉强度都比Q&P试样低,但由于I&QP试样中软相铁素体的存在以及残余奥氏体能发挥更好的TRIP效应,使得临界热处理的实验钢的伸长率更高,加工硬化指数增加,强塑积更大。 相似文献
16.
采用γ单相区和γ+α双相区轧制并淬火工艺以及双相区再加热-淬火-碳配分(IQ&P)工艺,研究预处理组织对低碳钢室温状态多相组织特征及力学性能的影响规律.实验用低碳钢经两种工艺轧制并淬火处理,获得马氏体和马氏体+铁素体的预处理组织,再经双相区IQ&P工艺处理后均获得多相组织.马氏体预处理钢的室温组织由板条状亚温铁素体、块状回火马氏体以及一定比例的针状未回火马氏体和8.2%的针状残余奥氏体组成;马氏体+铁素体预处理钢由板条状亚温铁素体、块状和针状未回火马氏体以及14.3%的短针状或块状残余奥氏体组成.在相同的双相区IQ&P工艺参数下,预处理组织为马氏体的钢抗拉强度为770 MPa,伸长率为28%,其强塑积为21560 MPa·%;而预处理组织为马氏体+铁素体的钢抗拉强度为834 MPa,伸长率增大到36.2%,强塑积达到30190 MPa·%,获得强度与塑性的优良结合. 相似文献
17.
X. Wang L. Liu R. D. Liu M. X. Huang 《Metallurgical and Materials Transactions A》2018,49(5):1460-1464
Compared to the quenching and partitioning (Q&P) steel produced by full austenization annealing, the Q&P steel produced by the intercritical annealing shows a similar ultimate tensile stress but a larger tensile ductility. This property is attributable to the higher volume fraction and the better mechanical stability of the retained austenite after the intercritical annealing. Moreover, intercritical annealing produces more ferrite and fewer martensite phases in the microstructure, making an additional contribution to a higher work hardening rate and therefore a better tensile ductility. 相似文献
18.
采用冷轧+两相区温轧退火(CR+WR+IA)热处理工艺,研究了两相区退火时间对超细晶铁素体与奥氏体中组织形貌演变、C和Mn元素配分行为以及力学性能的影响。结果表明,冷轧试验钢经两相区形变退火处理后,获得了由铁素体、残余奥氏体或新生马氏体组成的超细晶复相组织。在645℃随退火时间的延长,形变马氏体向逆相变奥氏体配分的C、Mn元素增多,C、Mn元素富集位置增加,同时富Mn区形变马氏体回复再结晶现象明显;伴随少量碳化物溶解,试验钢的屈服强度由741持续降低到325MPa。两相区退火10min时,试验钢力学性能最佳,此时抗拉强度达到最大值1141MPa,断后伸长率及均匀伸长率分别为236%和181%,强塑积达到26928MPa·%。 相似文献