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变形速率对普碳钢中形变诱导铁素体相变的影响 总被引:1,自引:0,他引:1
针对普通碳素钢(Q235类型),研究在Ae3~Ar3温度区间内采用形变诱导铁素体机制获得超细晶铁素体的数量与变形速率的相互关系。实验在Gleeble 1500热模拟实验机上进行。实验方案为:1000℃保温2min,以10℃/s的速度冷却到变形温度[Ae3(840℃)至Ar3(780℃)],变形量为30%~50%,变形后立即水淬。结果表明,在840℃变形时,随着变形速率的增大,形变诱导铁素体量增多;在780℃变形时,随着变形速率的增大,形变诱导铁素体量减少;而在840-780℃之间变形时,变形速率存在最佳值,在该值下诱导生成的铁素体量最大。 相似文献
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Hot deformation of a continuously cast low alloyed steel is studied by means of hot compression and tensile tests by using a Gleeble® 1500 machine after austenitization in a wide range of strain rates and between 720–800 °C. The flow data are evaluated to obtain the strain rate sensitivity and the processing maps. A new calculation method is used, yielding on the instability parameter defined as κJ which correlates well with the microstructural changes. The strain rate sensitivity does not predict any instability but all the others instability parameters do, including the new κJ. Flow instability appears at high temperatures and low strain rates where pores are formed at the austenitic grain boundaries, causing a decay of ductility in the tensile test. During hot deformation more ferrite is formed than corresponding heat treatments without deformation. In these conditions, the deformation is concentrated in the softer ferrite phase. The deformation induced ferrite deforms by dynamic recovery forming new grains as revealed by metallography and is correlated with low coefficients of power dissipation. The sinh type constitutive equation represents the flow data well with a stress exponent n = 4.1 and an apparent activation energy Q = 218 kJ/mol. 相似文献
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The phase transformation temperature of ordered β' to disordered β in the Cu-Zn alloy was tested by DSC. The transformation activation energy was calculated and the effect of deformation of the phase transformation was discussed. The results show that the phase transformation temperature and activation energy of ordered β' to disordered β in the Cu-Zn alloy can be decreased going through deformation, and the phase transformation time can be also decreased. As a result, the order-disorder phase transformation occurs more easily. 相似文献
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在Gleeble热模拟试验机上,研究含铌微合金钢中铌的析出物在形变诱导相变过程中的作用机理,结果表明:当加热温度为1000℃时,部分铌的碳化物未溶解于奥氏体中,而加热温度为1100℃时,铌的碳化物能够全部溶解到奥氏体中,含铌微合金钢加热温度范围约在1000~1100℃之间。铌的未溶解碳化物和在冷却过程中析出的碳化物都能作为铁素体形核位置,从而促进γ→α相变的发生。 相似文献
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Influence of Prior Austenite Deformation and Non-Metallic Inclusions on Ferrite in Low Carbon Steels
Abstract Effects of prior austenite deformation and non-metallic inclusions on the ferrite nucleation and grain refinement of two kinds of low carbon steels have been studied. The ferrites nucleation on MnS and V(C,N) is observed. The combination of thermal-mechanical processes with adequate amounts of non-metallic inclusions formed in low carbon steels could effectively refine the grain size and the microstructure. Ferrite nucleated on the single MnS or V(C,N) inclusions and complex MnS+V(C,N) inclusion. The proper addition of elements S and V could effectively promote the formation of ferrite and further refinement of ferrite grains. 相似文献
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Phase transformations driven by the change offree energy at equilibrium conditions have been wellestablished.In practice,however,thenonequilibrium transformation dominates in mostcases.The transformation of solidified weld metal toAF is completed during continuous rapid cooling.This process can hardly be described by the theoryof thermodynamics.Therefore,kinetics study iscalled.However,few have been reported about thekinetics of AF transformation in weld metal. In this paper,the kinetic… 相似文献
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Hot deformation processing was designed to study the effects of niobium (Nb) on DIFT. A prestrain of 051 at 880 ℃ for different isothermal time was used for adjusting the deformed austenite constitution and Nb existing state, followed by a secondary heavy deformation at 780 ℃ for inducing the ferrite transformation. The volume fraction and grain size of deformation induced ferrite (DIF) obtained at different isothermal time between double hits were investigated. It was found that Nb dissolved in austenite is adverse to DIFT; however, the precipitation of Nb is beneficial to DIFT. As Nb plays the role in the conventional TMCP, Nb retards the recrystallization of deformed austenite and enhances the deformation stored energy in the multipass deformation, and in result, Nb promotes DIFT. 相似文献
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The effects of large strain and strain path reversal on the deformation microstructure evolution in austenite below the recrystallisation temperature were studied by hot torsion using a non-transforming Fe-30wt%Ni model austenitic alloy.Results show that the high angle boundaries (HABs) can be generated by both microstructure mechanism through dislocation accumulation and texture mechanism via subgrain rotation.However,multiple strain path reversals lead to less well-developed HABs in the original grains compared to single reversal deformed to the same amount of total accumulative strain.This effect is attributed to the subgrain rotation mechanism being less effective at small strains.In comparison,the same hot torsion tests were conducted using a microalloyed steel at a temperature between Ae 3 and Ar 3.After single strain path reversal,substantial deformation-induced austenite-to-ferrite phase transformation was observed.Meanwhile,a test with multiple strain path reversals but with the same total strain produces much lower levels of strain-induced ferrite formation.This difference is correlated to the observations made in the Fe-30wt%Ni model alloy.It is believed that the different amount of strain-induced ferrite originated from the different levels of strain-induced HABs within the austenite which act as ferrite nucleation sites. 相似文献
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The high temperature deformation behavior of the 9Ni steel has been studied by the Gleeble-3500 tester. The relationship between deformation resistance and deformation degree, deformation temperature and deformation rate was revealed. The results show that when the deformation degree is less than 02, the deformation resistance increases by about 70 to 200 MPa, while the deformation degree varied between 02 and 04, the deformation resistance increases by about 30-40 MPa, when the deformation degree is larger than 04, the deformation resistance increases slowly, some become stable gradually. The influence of deformation temperature on deformation resistance is larger, and deformation resistance at higher temperature is about 160 MPa smaller than at lower temperature. Higher deformation rate leads to larger deformation resistance. The deformation resistance increases about 70 to 110 MPa with the increase of the deformation rate. A new and highly accurate mathematical model of the steel was established to describe the deformation behavior during rolling. 相似文献
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Effects of Deformation on Bainite Transformation During Continuous Cooling of Low Carbon Steels 总被引:4,自引:0,他引:4
ted alot of interests of metallurgical researchers.Aswell known,the steels with ultra-fine grains havepoor work hardening ability and high yield ratio[1].This problem can be solved through complexstrengthening mechanism in which some bainite isintroduced to ferrite matrix with suitable grain size.So it is necessaryto studythe transformation of aus-tenite to bainite inlowcarbon steels during continu-ous cooling after deformation.Most of the research works[2-4]about the trans-formation fromauste… 相似文献
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《钢铁研究学报(英文版)》2011,(Z1):377-382
The effect of vanadium on the DIFT (Deformation Induced Ferrite Transformation) microstructure coarsening in low carbon steel during the continuous cooling processes and isothermal processes at different temperatures were investigated using thermo-simulator.The results showed that the steel containing a small amount of vanadium had the similar velocity of grain growth with the vanadium free steel during the continuous cooling process,but a lower velocity of grain growth than that of vanadium free steel during isothermal processes at high temperatures.On the other hand,the vanadium remarkably inhibited grain growth in the steel containing a high amount of vanadium during both the continuous cooling and isothermal processes.Vanadium dissolved in matrix is indicated as an important factor on restraining grain growth through estimating the driving force of normal grain growth and the resistance of precipitation particles of vanadium on grain growth.The influencing mechanism of vanadium dissolved in matrix on the grain growth during the controlled cooling process is discussed. 相似文献
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介绍了各种合金结构钢(铁素体钢、铁素体 珠光体钢和淬火回火钢)的形变位错结构及循环形变位错结构的研究情况,阐述了沉淀硬化合金强化过程的位错缠结机制、静载和动载竞争机制以及循环微裂纹的萌生机制。 相似文献