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钢铁材料的晶粒细化研究 总被引:7,自引:0,他引:7
回顾了最近几年来在钢铁材料晶粒细化方面取得的一些研究成果,叙述了钢铁材料晶粒细化的目的与晶粒细化理论,阐述了目前常用的几种晶粒细化方法(微合金化、形变诱导相变、形变热处理等)的理论依据、适用条件、应用情况以及存在的问题,为今后材料科学工作者研究钢铁材料晶粒细化以及实际工程应用提供参考。 相似文献
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纳米WC/Co硬质合金粉末烧结早期的晶粒长大研究 总被引:8,自引:2,他引:8
研究了纳米晶粒WC/Co硬质合金烧结早期的晶粒长大问题,利用X射线衍射、TEM等技术对烧结过程中晶变化情况进行分析,并在此基础上探讨了烧结早期的晶粒长大机制。实验结果表明:WC晶粒长大在加热过程已经发生;晶粒开始长大温度为1000℃,在1100℃部分晶粒长大到100nm;在1200℃,有更显著的晶粒长大发生,有些尺寸达到400nm。烧结过程中WC晶粒形状变得规则化。烧结早期WC晶粒长大是在晶粒旋转合并机制与局部液相烧结机制共同作用下完成。 相似文献
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晶粒的平均截距和晶粒的弗里特直径及晶粒的公称直径是表示晶粒尺寸的三种方式,三者间存在着必然的联系。采用线性回归的方法对晶粒的平均截距、弗里特直径、公称直径进行回归分析,并从理论上进行了推导,认为晶粒的平均截距,弗里特直径,公称直径的关系是高度显著性的线性关系。同时,证实了研究所得到的回归方程的正确性。 相似文献
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李学富 《冶金标准化与质量》1996,(Z1)
1 中外晶粒度测定方法标准中晶粒度的叫法 经查阅中、俄、美、日、德、法、英及ISO晶粒度测定法标准,各国对晶粒度的叫法有: (1)GB6394—86只规定了“晶粒度是指晶粒大小的程度”,并规定了晶粒度的六种显示方法:(a)渗碳法;(b)网状铁素体法;(c)氧化法;(d)直接淬火硬化法;(e)网状渗碳体法;(f)网状珠光体(屈氏体)法。 相似文献
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通过热处理实验研究了热处理过程中FGH96合金的微观组织演化,量化了固溶温度和保温时间对晶粒尺寸、γ′相尺寸、面积分数及晶粒分布的影响,分析了γ′相和应变存储能对晶粒演变的影响。结果表明:在热处理过程中,含有大量应变存储能的变形晶粒发生静态再结晶,晶粒细化,而动态再结晶晶粒发生晶粒长大,当两者平衡时可获得均匀细小的晶粒组织。合金在1060℃保温120 min后,γ′相尺寸和晶粒尺寸分布较为均匀,平均晶粒尺寸为7.37μm。γ′相的面积分数随固溶温度和保温时间的增加而减小,一次γ′相在亚固溶保温过程中存在粗化和分裂现象,使得一次γ′相的面积分数和尺寸先增加后减小。γ′相的非均匀溶解会导致局部晶粒长大较快,形成混晶。 相似文献
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研究了6Cr21Mn10MoVNbN气阀钢在1 000℃到1 250℃固溶处理时的晶粒长大规律,并分析了等温固溶时晶粒长大的动力学.结果表明,弥散分布的碳氮化物对晶粒长大有显著阻碍作用,在低于该钢的晶粒粗化温度(1150℃)固溶处理时,大量未溶解的碳氮化物使得晶粒尺寸增幅较小、洛氏硬度小幅下降;在高于1150℃时,随温度的升高或时间延长,晶粒长大迅速,洛氏硬度大幅下降;晶粒生长指数随固溶温度的升高而呈台阶式增长;在固溶温度为1 050~1100℃下的晶粒长大激活能为189.9 kJ/mol,晶粒长大机理为自扩散过程控制机理,并建立了相应的晶粒长大动力学方程. 相似文献
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《Acta Metallurgica》1986,34(1):97-106
The kinetics of grain growth in a Zn-22% Al alloy during static annealing and superplastic deformation (SPD) is studied. SPD is found to enhance the rate of grain growth the stronger, the higher is the strain rate. The dependences of the grain growth rate on the strain rate, strain and annealing time are obtained. The contributions of static annealing and of deformation to the grain size increase are estimated. Possible mechanisms controlling the grain growth rate under static annealing and dynamic annealing are discussed. The rate of grain growth in the superplastic alloy is found to be controlled by solute diffusion along the grain boundaries. The mechanism of grain growth during SPD in the alloy is proposed which provides a good quantitative agreement with experimental data. 相似文献
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磷元素在钢中的晶界偏聚 总被引:5,自引:0,他引:5
磷元素在钢中的晶界偏聚可以分为两类,即平衡偏聚和非平衡偏聚.介绍了这两类偏聚现象以及偏聚理论.以磷对晶界结合力、晶界扩散和晶界能的影响机理为基础,分析了磷元素对钢力学性能的影响和磷在钢中发生晶界偏聚的原因. 相似文献
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《Acta Metallurgica》1989,37(5):1375-1379
The main analytic theories of grain growth driven by capillarity are reviewed. When grain growth is pictured as a grain drift process, the major problem is to derive the drift velocity equation. The simplest possible choice is based on a one-grain model and thus neglects some of the topological requirements of the system. When grain growth on the other hand is pictured as a diffusion process in grain size-time-space there are problems with the physical interpretation of the diffusion coefficient. The previous treatments of grain growth along this line are shown to contain some fundamental shortcomings. 相似文献
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为了从纳米尺度上探究与表征bcc-Fe的晶界变形行为,采用分子动力学方法分析了4种不同的bcc-FeΣ3晶界(Σ3(111)、Σ3(112)、Σ3(111)/(115)、Σ3(112)/(552))的拉伸与剪切变形过程,研究了晶界上空位和碳的原子分数对晶界拉伸和剪切性能的影响。结果表明,随着空位与碳原子所占晶界原子分数的增加,Σ3(112)晶界的拉伸应力-应变曲线屈服阶段逐渐消失。随着空位原子分数的升高,Σ3(111)晶界抗拉强度逐渐降低,而其余3种晶界抗拉强度也有不同程度的减小。含碳原子的Σ3(111)晶界抗拉强度有所增加,相反,其余3种晶界抗拉强度均低于原始无缺陷晶界。4种晶界的剪切强度均由于空位的存在或碳原子置换而明显减小。 相似文献
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Dong-Woo Suh Jae-Young Cho Kotobu Nagai 《Metallurgical and Materials Transactions A》2004,35(11):3399-3408
The microstructural evolutions of Ni-30Fe alloys during hot deformation are investigated. Hot-deformed structures of Ni-30Fe
alloys with initial austenite grain sizes of 20 and 140 μm are examined under various compressive strains and deformation
temperatures. As the initial austenite grain size decreases, dynamic recrystallization (DRX) occurs at lower compressive strain
and lower deformation temperature. At deformation temperatures where dynamic recovery occurs instead of the DRX, hot-deformed
structures consist of recovered elongated grains until fine-equiaxed grains are evolved by geometric DRX. Critical compressive
strain for the geometric DRX decreases with the decrease of initial austenite grain size. Geometric DRX is evolved by the
impingement of serrated grain boundaries. The decrease of initial grain size is considered to reduce the critical compressive
strain needed for the impingement of serrated grain boundaries. The changes in the effective thickness of austenite grain
according to the compressive deformation are examined and the effects of the restoration processes on the effective thickness
of austenite grain are discussed. 相似文献
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Min Wang Jianxin Zhou Yajun Yin Hai Nan Dongqiao Zhang Zhixin Tu 《Metallurgical and Materials Transactions B》2017,48(5):2245-2255
A 3D cellular automata model is used to simulate normal austenitic grain growth in this study. The proposed model considers both the curvature- and thermodynamics-driven mechanisms of growth. The 3D grain growth kinetics shows good agreement with the Beck equation. Moreover, the growth exponent and grain size distribution calculated by the proposed model coincides well with experimental and simulation results from other researchers. A linear relationship is found between the average relative grain size and the grain face number. More specifically, for average relative grain sizes exceeding ~0.5, the number of faces increases linearly with relative grain size. For average relative grain sizes <0.5, this relationship is changed. Results simulated by the proposed model are translated to physical meaning by adjusting the actual temperature, space, and time for austenitic grain growth. The calibrated results are found to be in agreement with the simulation results from other research as well as the experimental results. By means of calibration of the proposed model, we can reliably predict the grain size in actual grain growth. 相似文献
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混晶条带是影响GH2132合金组织及性能稳定性的重要因素,因此针对合金冷拉棒材出现的混晶条带缺陷进行了试验研究。利用金相、EPMA、EBSD和TEM手段,结合热力学平衡相图与硬度测试,揭示了混晶条带的主要成因,并分析了其内部微观组织状态及混晶组织对显微硬度的影响。结果表明,混晶条带组织中细晶区晶粒尺寸普遍小于10 μm,粗晶区晶粒最大可超过60 μm,而元素偏析与冷拉变形是造成晶粒大小差异并形成混晶条带的原因。合金铸态组织中Ti、Mo、C、B元素均表现出正偏析,其中C、Ti元素的偏析程度较高,能够在枝晶间析出MC与M3B2相,并最终遗传至奥氏体晶界;晶界溶质富集不仅起到钉扎作用,阻止再结晶过程晶粒长大,还能够通过溶质拖拽作用降低晶界的迁移速率而阻碍晶界变形,最终溶质富集区域形成细晶区、贫化区域形成粗晶区,并沿合金棒材组织冷拉方向表现出混晶条带。另外,在冷拉变形过程中,由于晶体取向不一,在受同样拉拔力条件下晶粒变形的实际应变并不一致,这也会加剧混晶现象。微观组织观察显示冷变形后细晶区与粗晶区相比形变更为均匀,组织内平均位错密度更高,混晶区域内存在退火孪晶与形变孪晶,但细晶区孪晶密度更高。最终混晶区存在的晶界数量不同、位错密度变化、孪晶分布的梯度组织,导致细晶区显微硬度明显高于粗晶区的硬度梯度。 相似文献