共查询到19条相似文献,搜索用时 109 毫秒
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1Cr18Ni9Ti不锈钢双辊薄带凝固组织区的形成机理 总被引:3,自引:0,他引:3
在双辊薄带连铸实验和薄带凝固组织特征分析的基础上,结合对薄带凝固组织区的模拟预测结果,研究了1Cr18Ni9Ti不锈钢双辊薄带凝固组织区(特别是等轴晶区)的形成机理.结果表明:1Cr18Ni9Ti不锈钢双辊薄带凝固组织中的等轴晶区不但在凝固类型为半固态时形成,在轧制或理想型时也能形成.其形成机理为,熔池中悬浮游离晶体的沉积、聚集以及在枝晶生长前沿的长大和薄带离开二铸辊最小间隙(铸辊出口)后,薄带/空气界面换热系数骤然降低抑制了柱状枝晶的生长,并促使薄带中部未凝固熔体中游离晶体的择优长大. 相似文献
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罗伟 《材料科学与工程学报》2000,18(2):94-99
研究了手工钨极氩弧焊对奥氏体不锈钢 0 Cr1 9Ni9和 1 Cr1 8Ni9Ti表面耐蚀性的影响 ,以及微束等离子弧重熔对焊接接头耐蚀性的影响。实验结果表明 ,通常焊接对奥氏体不锈钢的表面耐蚀性有不利影响 ,焊接热影响区及焊缝金属的耐蚀性 ,较母材有所降低。但经微束等离子弧表面重熔后 ,表面重熔层快速凝固 ,细化了重熔层组织 ,显微偏析减小 ,铬碳化物在晶界的沉淀析出得到抑制 ,故此焊接接头的耐蚀性得以显著提高。 相似文献
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为了保证不锈钢的耐蚀性,必须严格控制其含碳量。通过对小直径1Cr18Ni9Ti航空管抗晶间腐蚀性能与Ti,C含量的关系进行了分析,并进行了提高其抗晶间腐蚀性的针对试验研究。研究结果表明,将C含量控制在0.025~0.045%之间,Ti含量控制在0.2%~0.4%之间,即Ti,C含量比值约为8~11时,1Cr18Ni9Ti钢管抗晶间腐蚀性较好;采用低温燃烧除酯,可以有效避免在制管过程中增加1Cr18Ni9Ti钢管的含碳量,从而提高其耐蚀性;配以适当的稳定化处理,也可以在一定程度上提高1Cr18Ni9Ti钢管的抗晶间腐蚀性能。 相似文献
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《理化检验(物理分册)》2016,(3)
通过对0Cr18Ni10Ti不锈钢力学性能的研究,论证了在炉体外延式高温引伸支架上加装外置式常温引伸计测试钢材高温下规定非比例延伸强度Rp0.2方法的可行性,并对高温试验后的0Cr18Ni10Ti不锈钢试样进行了宏观检验。通过对0Cr18Ni10Ti不锈钢在不同温度和保温时间下进行拉伸试验,探讨了受热温度和保温时间对其力学性能的影响。最后通过回归分析,得出了规定非比例延伸强度Rp0.2和抗拉强度Rm随温度变化的规律。 相似文献
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S. D. Felicelli P. K. Sung D. R. Poirier J. C. Heinrich 《International Journal of Thermophysics》1998,19(6):1657-1669
Nickel superalloys that are used in the high-temperature regions of gas-turbine engines are cast by directional solidification (DS). In the DS processes, the castings are cooled from below, and three zones exist during solidification: (1) an all-solid zone at the bottom, (2) a “mushy zone” that is comprised of solid and liquid material, and (3) an overlying all-liquid zone. Computer simulations can be useful in predicting the complex transport phenomena that occur during solidification, but realistic simulations require accurate values of the transport properties. In addition to transport properties, the thermodynamic equilibria between the solid and liquid during solidification must also be known with reasonable accuracy. The importance of using reasonably accurate estimations of the transport properties is illustrated by two-dimensional simulations of the convection during solidification and the coincidental macrosegregation in the DS castings of multicomponent Ni-base alloys. In these simulations, we examine the sensitivity of the calculated results to measured partition ratios, thermal expansion coefficients, and viscosities that are estimated by regression analyses and correlations of existing property data. 相似文献
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Investigations were made, using scanning electron microscopy, to examine microstructural features of laser coatings. The scanning electron microscope makes it possible to observe clearly the detail of the structure in the laser-irradiated zone. It is shown that the microstructures in the laser-coated zone have various features, including a dendritic eutectic, dendritic solid solution, and residual graphite, and that the microstructures in the transitional zone are more complex, including cellular dendritic-cellular, dendritic eutectic, planar, and residual graphite. The laser coating process changes the nature of solidification of the coating melt, compared with common solidification. 相似文献
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H. Jones 《Journal of Materials Science》1984,19(4):1043-1076
The status of rapid solidification is discussed in terms of recent progress in modelling methods of achieving solidification at high cooling rates and its effects on alloy constitution and microstructure. Applications currently in view are reviewed under the following headings: high-strength structural materials; tool and bearing materials; high-temperature materials, corrosion-resistant, catalytic and storage materials; and electrical and magnetic materials. It is concluded that the future of rapid solidification is not identifiable with any one process, activity or application and that many unresolved questions remain to challenge both the scientific and business communities. 相似文献
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This investigation has been performed to characterize dissimilar metal welds between type 310 austenitic stainless steel (SS)
and Inconel 657 superalloy. The welds were produced using four types of filler materials: Inconel 82, Inconel A, Inconel 617,
and type 310 SS. The weldments were characterized in detail using optical metallography and scanning electron microscopy.
It can be concluded that Inconel A weld metal does not promote severe hot cracking. Continuous NbC precipitates in the Inconel
82 weld metal can sensitize the weld metal to solidification cracking. The presence of high amounts of Mo in Inconel 617 weld
metal led to the formation of brittle phases. In addition, continuous precipitates were observed in the 310 SS weld metal,
which can lead to poor resistance of the weld metal to hot cracking. In the aged condition, Inconel 82 and Inconel A exhibited
good thermal stability, whereas Inconel 617 and type 310 SS exhibited poor thermal stability. Also, after subjecting the heat-affected
zone and interface between Inconel weld metal and base metals to aging treatment, unmixed zone of Inconel 657 base metal side
has disappeared. Elimination of this region can be attributed to high-temperature interdiffusion of alloying elements. Finally,
it is found that Inconel A and Inconel 82 weld metals are the best choices for the dissimilar welds performed here, respectively. 相似文献
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Damage-free processes of grinding of brittle materials have been widely used in industry for producing electronic and optical components with high surface integrity. It has been found that the transition threshold from ductile flow to brittle fracture during the process of material removal plays a central role in the quality control of a machined surface. However, the precise microscopic mechanism which governs the formation of dislocation structure and micro-cracking when machining a brittle material such as alumina, remains unclear. The mechanism of formation and structure of the plastic or damage zones in alumina of two different grain sizes (1 and 25 m) subjected to single-point scratching with sharp and blunt indenters were studied in this paper. Using transmission electron microscopy, characteristic features of the plastic/damage zone in terms of loading conditions and microstructure of the materials were carefully investigated. It was found that the grain size and the geometry of the indenter had a great effect on the dislocation structure of the plastic zone and that the subsurface damage could be very severe, even though the machined surfaces appeared damage-free. These results indicate that the ductile flow to brittle fracture transition in machining brittle ceramics is more complicated than previously thought and that a reliable criterion has yet to be established to predict a real damage-free grinding process. 相似文献
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Zhifu Wang Haitao Wang Shouren Wang 《Science and Technology of Advanced Materials》2013,14(1):297-302
In order to design a new kind of low-cost high-temperature ferrite-austenite duplex alloy, the effects of carbon and chromium on the alloy solidification structure and properties have been investigated with orthogonal experiments. The addition of carbon promotes strongly the formation of austenite and that of carbides in the alloy solidification structure and refines the alloy grains. With the increase of carbon content, the alloy high temperature strength and oxidation resistance at 1250°C improves at first, but then begins to deteriorate greatly when the carbon content exceeds 0.15%. The addition of chromium facilitates the formation of ferrite in the alloy solidification structure. As the chromium content increases, the alloy rupture strength at 1250°C initially is enhanced, but then reduces rapidly, while the alloy oxidation resistance improves continuously. 相似文献
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将AZ61镁合金液态凝固过程分为高温熔体和凝固两个阶段,研究各阶段冷却速率对铸态组织的影响,不同冷速下铸态合金枝晶间距的变化及其对显微硬度的影响。结果表明:在高温熔体阶段随着冷却速率从0.65℃/s增加到15.9℃/s,枝晶组织不断细化且尺寸更均匀,一次枝晶间距从230μm逐渐减小到80μm,二次枝晶间距从12.8μm逐渐减小到9.2μm;凝固阶段在7.8℃/s至23.0℃/s不同冷却速率下,一次枝晶间距从105μm逐渐减小到73μm,二次枝晶间距从10.6μm逐渐减小到8.8μm。两个阶段显微硬度值随冷却速率增大都呈增高趋势。相对于凝固阶段,高温熔体阶段的冷却速率变化对铸态凝固组织的影响更显著。 相似文献
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由于单晶高温合金消除了晶界这一高温薄弱结构,已成为航空发动机首选的热端部件材料。为了满足航空发动机对推重比和涡轮燃气温度的更高需求,新型单晶高温合金中添加了越来越多的Re、Ru等难熔元素,致使单晶制备过程中缺陷形成倾向显著提高,研制周期和研制成本明显增加,严重限制了单晶高温合金的产业化应用。近年来,随着计算方法和熔模铸造技术的发展,数值模拟在单晶高温合金制备领域中得到了越来越广泛的应用,已成为减少单晶铸造缺陷,获得高质量单晶铸件的重要手段。以商用铸造模拟软件Procast为例,对单晶高温合金定向凝固过程的温度场分布和组织演化进行了分析,综述了数值模拟在单晶熔模铸造研究中的应用现状。首先,介绍了数值模拟中的前处理过程,即几何建模、网格划分等,强调了前处理过程的注意事项。随后,根据已有文献,分析了数值模拟技术在研究温度场和晶粒组织演化过程的作用。最后,指出数值模拟技术在单晶高温合金熔模铸造领域进一步发展需要解决的问题。 相似文献