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45钢等径弯曲通道变形及组织细化研究 总被引:2,自引:0,他引:2
研究了等径弯曲通道(ECAP)变形后45钢中先共析铁素体及珠光体组织的演变特征.结果表明,ECAP变形4道次后,片层状的珠光体组织演变成了超细的渗碳体颗粒均匀分布于亚微晶铁素体基体的组织.先共析铁素体由原始的平均晶粒尺寸约为30 μm演变为大角度晶界分离的、平均晶粒尺寸约为0.4μm的超细晶组织.ECAP变形后,先共析铁素体首先在其内部会形成具有薄片层界面(LBs)的板条位错胞甚至亚晶组织.进一步变形时位错胞或亚晶可继续细化.再进一步变形时通过晶界滑移和晶粒旋转的方式可以获得具有大角度晶界分离的、等轴的超细晶组织. 相似文献
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剧烈塑性变形后超细晶粒耐蚀钢的强度 总被引:1,自引:0,他引:1
给出了Cr-Ni奥氏体耐蚀钢经剧烈塑性变形可得到纳米级或亚微晶结构的研究结果。经高压扭转变形后,其平均晶粒尺寸约为50nm,而经等径弯曲通道变形后,一般可获得带有被分割晶粒(其尺寸为100-250nm)的取向结构。采用高压扭转变形或等径弯曲通道变形法进行剧烈塑性变形可促进马氏体转变,相应得到的Cr-Ni奥氏体钢表现出较强的加工硬化性能。 相似文献
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含铌非调质钢的组织与性能 总被引:2,自引:0,他引:2
简单介绍了含铌非调质钢35MnVNb的金相组织与力学性能。35MnVNb钢通过适当控制热变形工艺,可以得到均匀的铁素体和珠光体组织,用QA-b图像分析仪测定了珠光体体积百分数,结果为Φ16~Φ45mm轧材的铁素体晶粒和珠光体团的平均尺寸为11.5~19.5μm,相当于9.7级和8.2级晶粒度;Φ80mm锻材的晶粒度平均尺寸为35.2μm,也达到7级。含铌非调质钢奥氏体连续冷却转变曲线说明,要得到铁素体和珠光体组织,最大冷却速度为3.6℃/s,高于此冷速,将产生贝氏体组织,对钢的韧性有严重的影响。 相似文献
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为了实现Cu-P-Cr-Ni-Mo耐候钢的铁素体晶粒细化从而充分提高其强塑性,通过热模拟压缩试验,利用金相、SEM、EBSD等微观组织分析方法研究了其在双相区的多道次压缩变形过程中的组织演变。结果表明,试验钢在变形过程中,第二相(马氏体、贝氏体)呈条带状分布于铁素体基体上,随着道次增加,铁素体晶粒逐步细化,第5道次变形后得到1.8 μm左右的超细晶铁素体。前期铁素体晶粒细化的主要机制是形变强化铁素体相变,即多道次的累积大变形使组织内畸变能增大,铁素体形核点增多,促进铁素体快速析出,形成细小铁素体晶粒;后面几道次变形中,随着应变量继续增大,在铁素体晶粒内形成大量亚晶界,且亚晶界逐步累积扭转成大角度晶界,分割原来的粗大晶粒,发生铁素体连续动态再结晶细化。 相似文献
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采用Gleeble热模拟试验机研究了形变温度及冷却速度对ML35钢显微组织与硬度的影响;对比分析了10B21钢SM控冷盘条和板链式控冷盘条的显微组织差异,用Minitab软件统计分析了显微组织对盘条拉拔性能的影响。结果表明:当ML35钢形变温度为750℃时晶粒明显细化,部分珠光体发生退化,渗碳体呈短棒状或颗粒状,但硬度相对偏高;降低形变后的冷却速度可粗化晶粒,降低硬度;粗大的铁素体+珠光体组织比细小的铁素体+珠光体组织具有较高的初始加工硬化率;并且在初始变形过程中,具有相对粗大的铁素体+珠光体组织盘条的断后伸长率下降偏快。 相似文献
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等径弯曲通道变形对超低碳钢组织及性能的影响 总被引:1,自引:0,他引:1
研究了室温下C方式等径弯曲通道变形(ECAP)对超低碳钢组织及性能的影响。结果表明:第1道次ECAP变形后,组织细化效果最显著;随变形道次的增加,组织由取向差小的板条状亚晶演变成取向差大的等轴晶;第4道次ECAP变形后,晶粒平均尺寸约03 μm;变形道次继续增加,晶粒尺寸变化不显著,而晶粒取向差不断增大。这表明第4道次ECAP变形为超低碳钢细化极限;ECAP变形可大幅度提高超低碳钢的强度,并保持较高的塑性。 相似文献
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The microstructural evolutions of the cold rolled Fe-0.1C-5Mn steel during intercritical annealing were ex- amined using combined advanced techniques. It was demonstrated that intercritical annealing results in an ultrafine granular ferrite and austenite duplex structure in cold rolled 0.1C-5Mn steel. The strong partitioning of manganese and carbon elements from ferrite to austenite was found during intercritical annealing by scanning transmission elec- tron microscopy (STEM) and X-ray diffraction (XRD). Strong effects of boundary characters on the austenite for- mation were indicated by austenite fast nucleation and growth in the high angle boundaries but sluggish nucleation and growth in the low angle boundaries. The ultrafine grained duplex structure in 0.1C-5Mn was resulted from the the sluggish Mn-diffusion and the extra high Gibbs free energy of ferrite phase. Based on the analysis of the micro- structure evolution, it was pointed out that the intercritical annealing of the medium Mn steels could be applied to fabricate an ultrafine duplex grained microstructure, which would be a promising approach to develop the 3rd genera- tion austomobile steels with excellent combination of strength and ductility. 相似文献
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Hot torsion testing was performed on a low carbon Nb-Ti microalloyed steel to study the effects of hot torsion parameters, strain and strain rate, on ultrafine ferrite grains production through dynamic strain-induced transformation, at a deformation temperature just above Ar3. The initiation and evolution of ultrafine ferrite grains were studied. The results show that the amount of strain and strain rate has conversely effect on the volume fraction and grain size of ultrafine ferrite grains. With increasing strain, the interior of austenite grains become activated as nucleation sites for fine ferrite grains. As a result, ferrite grains continuously nucleate not only at the former austenite grain boundaries but also inside the austenite grains which leads to a rapid increase in volume fraction of ultrafine grains. Increasing of strain rate reduces the tendency of ferrite grains coarsening so that ultrafine ferrite grains are achieved, while the volume fraction of ultrafine grains decreases at the same strain level. 相似文献
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A combination of extrusion and equal channel angular pressing (ECAP) was used to deform a plain low carbon steel. This process consists of two successive deformations by extrusion and ECAP in a single die (Ex-ECAP). Cylindrical samples were heated to predefined temperatures (650 and 850 ℃) and then pressed through a die channel with crosshead speed of 10 mm/s. Microstructure and resultant mechanical properties of processed material were studied. The results showed that pressing temperature has a significant effect on the resultant microstructure. While at 650 ℃, the cold worked structure with elongated ferrite grains were obtained, and at 850 ℃ the microstructure consisted of elongated ferrite grains and very fine grains at their boundaries as a consequence of continuous dynamic recrystallization (CDRX) of ferrite phase. Also at 850 ℃, a particular microstructure consisted of cold worked ferrite and static recrystallized grains on shear bands was obtained. 相似文献
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借助于光学显微镜研究了磁场(12 T)对Fe 0.76%C合金在807 ℃奥氏体化保温不同时间(10 min、30 min、60 min)后以2 ℃/min的冷速冷却后,先共析铁素体显微组织的形貌变化。结果表明:在相同奥氏体化保温时间下,经强磁场热处理样品的先共析铁素体的面积分数和晶粒数量明显高于无磁场热处理样品。这可归结为强磁场降低了先共析铁素体形核所需的驱动力。随着奥氏体化保温时间的延长先共析铁素体晶粒沿着强磁场方向伸长的趋势明显变弱。这主要是由于奥氏体晶粒随着奥氏体化保温时间的延长逐渐增大,导致铁素体晶核之间的距离增大,从而造成奥氏体中的Fe原子向先共析铁素体晶粒扩散的距离增大所致。 相似文献
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Kyung-Tae Park Yong-Seog Kim Dong Hyuk Shin 《Metallurgical and Materials Transactions A》2001,32(9):2373-2381
Two grades of low-carbon steel, one containing vanadium and the other without vanadium, were subjected to equal channel angular
pressing (ECAP) at 623 K up to an effective strain of ∼4. After equal channel angular pressing, a static annealing treatment
for 1 hour was undertaken on both pressed steels in the temperature range of 693 to 873 K. By comparing the microstructural
evolution during annealing and the tensile properties of the two steels, the effect of the addition of vanadium on the thermal
stability of ultrafine-grained (UFG) low-carbon steel fabricated by intense plastic straining was examined. For the steel
without vanadium, coarse recrystallized ferrite grains appeared at annealing temperatures above 753 K, and a resultant degradation
of the strength was observed. For the steel containing vanadium, submicrometer-order ferrite grain size and ultrahigh strength
were preserved up to 813 K. The enhanced thermal and mechanical stabilities of the steel containing vanadium were attributed
to its peculiar microstructure, which consisted of ill-defined pearlite colonies and ultrafine ferrite grains with uniformly
distributed nanometer-sized cementite particles. This microstructure resulted from the combined effects of (a) the preservation
of high dislocation density providing an effective diffusion path, due to the effect of vanadium on increasing the recrystallization
temperature of the steel; and (b) precipitation of fine cementite particles at ferrite grain boundaries through the enhanced
diffusion of carbon atoms (which were dissolved from pearlitic cementite by severe plastic straining) along ferrite grain
boundaries and dislocation cores. 相似文献
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JIANG Jinghua MA Aibin SAITO Naobumi SHEN Zhixin SONG Dan LU Fumin Yoshinori NISHIDA YANG Donghui LIN Pinghua 《中国稀土学报(英文版)》2009,27(5):848-852
Significant grain refinement was achieved in rare earth (RE) containing aeronautic magnesium alloy ZE41A through equal-chan-nel angular pressing (ECAP) using rotary die at 603 K. Influence of ECAP pass number on its microstructure change and corrosion behavior was investigated by optical microscope (OM)/scanning electron microscope (SEM) observation and potentiostatic polarization tests in aque-otis solution of NaCl, respectively. The results showed that ultrafine equiaxial grains (about 2.5 μm) were obtained over 16 passes due to plastic-induced grain refinement accommodated by dynamic recrystallization. The lower corrosion current density and nobler corrosion po-tential correlated with large number of pressing passes were attributed to the low tendency toward localized corrosion with broken secondary phase after homogenization on ultrafine-grained Mg matrix. The multi-pass ECAP method made the ZE41A aeronautic magnesium alloy more attractive since severe plastic deformation may significandy improve its corrosion resistance besides superior mechanical properties. 相似文献
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Machining chips of commercially pure titanium (ASTM Grade 2) were recycled into fully dense bulk material by equal channel angular pressing (ECAP). The morphology of the oxide layer derived from chip surfaces was characterized by focused ion beam miller and transmission electron microscopy. Electron backscatter diffraction and chemical analysis were used to propose quantitatively a complex strengthening mechanism considering interstitials, ultrafine grains (with misorientation ≥15 deg), and subgrains (<15 deg) substantially in existence after ECAP. 相似文献