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基于Ti—X二元相图提出了一种精确计算钛合金α+β/β相变点的方法,并根据该方法给出了一个计算公式。用该公式对几十个合金的相变点进行了计算,并与实测值进行了对比,除个别合金偏差较大外,其余合金的相变点计算值与测试值相差一般不超过±5℃。这表明该方法和公式涵盖面广、精确度高,适用于绝大多数钛合金的相变点计算。 相似文献
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采用热膨胀仪测试研究了Q450NQR1钢连铸坯5℃·min-1及20℃·min-1冷却速率下的线性热膨胀(ΔL/L0)和热膨胀系数随温度的变化规律.在此基础上,建立了一种基于平均原子体积的相体积计算模型,量化研究了奥氏体相变过程中各相体积分数的变化规律,并在将计算结果与显微组织观察结果对比分析基础上,讨论了连铸冷却速率对铸坯奥氏体相变过程的影响.结果表明:该计算模型可以较为准确地描述铸坯的奥氏体相变过程,适用于多相连续析出相变;随着冷却速率的增大,铸坯热膨胀曲线中对应于铁素体和珠光体析出的两个变化峰向低温区移动,峰值明显增大;冷却速率由5℃·min-1上升至20℃·min-1时,铁素体及珠光体起始析出温度分别降低约32℃和37℃,最终体积分数分别由0.894和0.106变为0.945和0.055. 相似文献
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随着材料科学技术的发展,相变储热材料应用愈来愈广泛,文章基于相变储热材料研究方面的调研,对其进行分类与介绍,并概述了该材料潜在的应用,同时为相变储热材料的研究指出了发展方向. 相似文献
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热轧后的带钢表面会形成氧化铁皮,其中的FeO在卷取之后的冷却过程中会发生共析相变,形成由Fe与Fe3O4共同组成的共析组织。传统对FeO共析相变的研究,多集中在诸如化学成分、相变环境等因素对共析反应的定性分析上,但针对相变的具体进程却少有模型化的分析和计算。同时,由于实际生产中FeO的相变过程多是在连续冷却过程中发生,相变过程受到了不同时刻温度变化的叠加影响,这也加大了研究的困难程度。为此,以常见的普碳钢为例,首先使用同步热分析仪进行了不同温度及时间下氧化铁皮的等温结构转变试验,统计了30个试验节点下的共析组织在FeO中的体积分数,之后基于Johnson-Mehl-Avrami-Kolmogorov(JMAK)方程建立了FeO在等温过程下共析相变的动力学模型,通过试验数据求解其中的关键参数,得到了等温转变条件下FeO中共析组织体积分数与时间的关系,可直接绘制描述FeO共析转变的Time-Temperature-Transformation(TTT)曲线。在此基础上,结合Scheil可加性法则,建立了连续冷却过程中FeO的共析相变模型,通过计算... 相似文献
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本文利用Hillert-Staffanson模型计算了Fe-1.33Mn-0.47C(at%)系Y→α相变驱动力G_v~Y→α。结果表明,ΔG_V~Y→α与温度的关系可以简单地表示为相关系数为0.9992。这一计算结果适用于成分与之相近的C-Mn钢和微合金钢的Y→α相变驱动力估算。 相似文献
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Effect of Niobium on Isothermal Transformation of Austenite to Ferrite in HSLA Low-Carbon Steel 总被引:2,自引:1,他引:1
CAO Jian-chun LIU Qing-you YONG Qi-long SUN Xin-jun 《钢铁研究学报(英文版)》2007,14(3):51-55
Using thermomechanical simulation experiment,the kinetics of the isothermal transformation of austenite to ferrite in two HSLA low-carbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation.The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism,wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation,whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs,wherein,the nucleation rate of ferrite in the initial stage of transformation is low,and in the second stage,the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete.Using carbon extraction replica TEM,niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite.The mechanism of the effect of niobium on the isothermal transformation was discussed. 相似文献
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为了研究中碳高强贝氏体钢中的残余奥氏体体积分数在不同等温情况下的变化规律,通过X射线衍射试验、热模拟试验和扫描电子显微镜观察等,分析了等温淬火条件对中碳高强贝氏体钢中残余奥氏体体积分数和组织的影响。结果表明,最终残余奥氏体的体积分数受贝氏体相变和马氏体相变的共同影响。贝氏体相变量决定了未转变奥氏体的体积分数及其化学稳定性,从而影响随后的马氏体相变量及最终残余奥氏体体积分数。此外,随着相变温度的升高,开始由于贝氏体相变量逐渐减少,残余奥氏体体积分数先增加(300~350 ℃),随后由于马氏体相变量增加,残余奥氏体体积分数减少(350~400 ℃)。 相似文献
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基于电子背散射衍射(EBSD)技术,利用极射赤面投影图,提出了一种不依赖于残余奥氏体,对协变相变产物的原奥取向进行重构的简易方法.计算结果表明,利用铁素体的{110}α极图中三个贝恩组的交点可以成功重构出原始奥氏体取向,并且精度可达2°;同时,该方法还可以对局部微区或者变体选择很严重的原奥取向进行重构,误差仍可控制在2°之内,具有其他重构方法无可比拟的优点.位向关系具体种类并不影响对原奥取向的重构,采用该方法进行原奥取向重构时不需要预先知道具体的位向关系,并且适用于位向关系处在K-S与N-W关系之间的所有协变相变过程.通过运用该方法重构原奥取向,本文研究了高温奥氏体化过程中的奥氏体行为.研究发现当采用较高的温度奥氏体化时会出现奥氏体孪晶,奥氏体孪晶的出现与奥氏体化温度有关. 相似文献
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Deformation affects the microstructure and morphology of the parent austenite, which affects the subsequent bainite transformation. The effects of ausforming on bainite transformation and microstructure were investigated by means of thermal simulation experiment, TEM and SEM etc. Different deformation temperatures and deformation strains were designed. The amount of bainitic transformation during isothermal holding and the volume fraction of retained austenite at room temperature were analyzed. The results show that the isothermal bainitic transformation is promoted by the deformation at 300?? and 400??. Moreover, the lower deformation temperature leads to larger amount of bainite. In addition, the volume fraction of retained austenite increases with the increase of the deformation strain, and more retained austenite can be obtained by decrease the deformation temperature. It indicates that deformation at lower temperature contributes to the mechanical stabilization of austenite. 相似文献
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Effect of Warm-Rolled Pearlite Microstructural Features on Austenitic Transformation 总被引:1,自引:0,他引:1
The austenite transformation characteristics for various warm-rolled pearlite during rapid heating were investigated. The results indicate that the start temperature (Ts) is sensitive to the microstructural feature of pearlite,whereas the dislocation plays an important role in the transformation rate; at the same time, the uniformity of austenite grains is more or less affected by the amount of spheroidized pearlite. A critical effect on the state of austenite grain is created through the influence of initial microstructures on the start temperature of transformation. 相似文献
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The giant stress-impedance (GSI) effect in as-cast and DC current annealed Co71.8Fe4.9Nb0.8Si7.5B15 amorphous glass-covered wires is presented. The SI ratio of the as-cast sample exhibits negative GSI effect. For the sample annealed by 60 mA DC current, the SI ratio first increases with applied tensile stress, then decreases with the applied tensile stress. The maximum ΔZ/Z ratio of 304% is obtained. Frequency dependence in the range from 1 to 110 MHz of the GSI effect is investigated. Experimental results show that the real part R and the imaginary part X of impedance play an important role at high frequency and low frequency, respectively. At 1 MHz, the maximum ΔX/X of 1 448% is obtained. At 110 MHz, the maximum ΔR/R ratio of 648% is obtained. 相似文献
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The effect of compressive deformation of austenite on continuous cooling transformation microstructures for 22CrSH gear steel has been investigated using a Gleeble 1500 thermal simulator. The experimental results show that the deformation of austenite promotes the formation of proeutectoid ferrite and pearlite, and leads to the increase of critical cooling rate of proeutectoid ferrite plus pearlite microstructure. The grain boundary allotriomorphic ferrite occupies the austenite grain surfaces when the prior deformation takes place or the cooling rate is decreased, which causes a transition from bainite to acicular ferrite. The deformation enhances the stability of transformation from austenite to acicular ferrite, which results in an increase of M/A constituent. 相似文献
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本文利用Formastor-Press压力膨胀仪测试09MnVTiN钢热变形后再结晶奥氏体的连续冷却转变动力学曲线,并用金相法分析不同阶段淬火试样的组织。结果表明,再结晶控轧后,奥氏体区的冷却速度(1000~820℃)对再结晶奥氏体的晶粒尺寸和随后的连续冷却转变动力学都有影响。 相似文献