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Jiu-han Xiao Wei-guo Jiang Dong-yu Han Kai-wen Li Guo-jun Tong Yu-zhang Lu Lang-hong Lou 《中国铸造》2022,19(1):35-45
Single-crystal rods with different diameters and deviation angles with respect to the solidification direction were produced by Bridgman rapid solidification method at withdrawal rates of 3 and 6 mm·min-1 and used as grain continuators.The crystallographic orientation of the rods,which cross-sections were perpendicular to the solidification direction at different solidification heights,was measured by electron backscattered diffraction,while the corresponding microstructures were observed by optical microscopy.The mushy zone morphology and the distribution of the temperature gradient were simulated by the finite element analysis software ProCAST.The experimental results indicate that the crystallographic orientation of the single-crystal rods corresponds to the statistical average value of all the dendrite orientations in cross-section.The crystallographic orientation of the primary and secondary dendrites of each single-crystal rod at different cross-sections fluctuates irregularly within a small range(less than 4°).The crystallographic orientation of the dendrite in each single-crystal rod is not exactly consistent with each other and is affected by their branching mode of dendrites in the solidification space.In addition,the simulation results show that the mushy zone shapes and the temperature gradient of single-crystal rods change with the increase of solidification height during the solidification process.Finally,the evolution mechanism of the crystallographic orientations and the corresponding influence factors were analyzed and discussed. 相似文献
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Using a mixture of the gas-atomized Ni52.5Nb10Zr15Ti15Pt7.5 and Fe73Si7B17Nb3 glassy alloy powders, we produced the two-phase bulk metallic glass (BMG) with high strength and good soft magnetic properties as well as satisfying large-size requirements by the spark plasma sintering (SPS) process. Two kinds of glassy particulates were homogeneously dispersed each other. With an increase in sintering temperature, density of the produced samples increased, and densified samples were obtained by the SPS process at above 773 K. Good bonding state among the Ni- and Fe-based glassy particulates was achieved. 相似文献
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Erlin Zhang Chunming Zou Guoning Yu 《Materials science & engineering. C, Materials for biological applications》2009,29(1):298-305
Silicon-substituted hydroxyapatite (Si-HA) coatings with 0.14 to 1.14 at.% Si on pure titanium were prepared by a biomimetic process. The microstructure characterization and the cell compatibility of the Si-HA coatings were studied in comparison with that of hydroxyapatite (HA) coating prepared in the same way. The prepared Si-HA coatings and HA coating were only partially crystallized or in nano-scaled crystals. The introduction of Si element in HA significantly reduced P and Ca content, but densified the coating. The atom ratio of Ca to (P + Si) in the Si-HA coatings was in a range of 1.61–1.73, increasing slightly with an increase in the Si content. FTIR results displayed that Si entered HA in a form of SiO4 unit by substituting for PO4 unit. The cell attachment test showed that the HA and Si-HA coatings exhibited better cell response than the uncoated titanium, but no difference was observed in the cell response between the HA coating and the Si-HA coatings. Both the HA coating and the Si-HA coatings demonstrated a significantly higher cell growth rate than the uncoated pure titanium (p < 0.05) in all incubation periods while the Si-HA coating exhibited a significantly higher cell growth rate than the HA coating (p < 0.05). Si-HA with 0.42 at.% Si presented the best cell biocompatibility in all of the incubation periods. It was suggested that the synthesis mode of HA and Si-HA coatings in a simulated body environment in the biomimetic process contribute significantly to good cell biocompatibility. 相似文献
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为研究Al-Si9-Cu3-Fe合金发动机缸体材料特性,建立该缸体热负荷分析模型对该发动机缸体进行有限元热-固耦合分析,采用对流换热分析模型进行有限元分析其在受热条件下的应力、在螺栓载荷下的应力与燃气压力条件下的材料应力,分别求得机械应力场和温度场综合热-固耦合模型应力,得出应力云图。分析结果表明:合金发动机缸体各项应力都小于材料最大屈服极限,发动机气缸体满足设计要求。 相似文献
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15MnB钢的化学成分和生产工艺决定了材料中极易出现MnS和TiN这两种夹杂物,研究了15MnB钢中S、Ti两种元素对夹杂物的产生及冲击性能的影响。设计不同S元素、Ti元素含量的15MnB钢,采用相同锻造、轧制及热处理工艺处理后,检测其冲击性能。采用光学显微镜观察试样的显微组织和夹杂物形貌,并用扫描电镜及能谱仪对夹杂物的化学成分进行检测。结果表明:S元素含量≤0.0029%,Ti元素含量≤0.03%时,15MnB钢的冲击性能最优;S元素含量≤0.0029%时,材料中形成的夹杂物数量少且尺寸小,15MnB钢的冲击性能稳定性随其含量减少而增强;Ti元素含量≥0.06%时,材料中会形成大量尺寸较大的TiN导致15MnB钢冲击性能大幅度降低。为了获得良好且稳定的冲击性能,建议企业在生产15MnB钢时严格控制夹杂物种类和等级,具体要求:D类(细系)≤1.0级、TiN≤0.5级,不应存在其他类型的夹杂物。 相似文献
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通过金相法进行了TC4-DT钛合金相变点温度Tβ测定,并利用热膨胀法进行了验证。对不同冷却速度下TC4-DT钛合金的热膨胀量曲线进行测绘,结合显微组织分析和硬度测试,绘制了TC4-DT钛合金的SH-CCT曲线。结果表明,TC4-DT钛合金的相变温度为(945±5) ℃。当冷速小于10 ℃/s时,由β相转变的α相呈不同取向的集束状,同时,晶内出现网篮状α相;当冷速大于10 ℃/s后,组织为马氏体α′相+块状αm相;当冷速超过100 ℃/s后,组织为马氏体α′相。TC4-DT钛合金发生马氏体转变的开始温度为836 ℃,终了温度为760 ℃。 相似文献
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《材料科学技术学报》2019,35(11):2658-2664
Foam structure materials are well known for their lightweight,efficient,and broadband microwave absorption properties compared to bulk material.However,little has been understood about the effect of a foam structure on the absorption performance of the foam material.In this study,the role of foam structure properties of the silicon carbide/carbon(SiC/C) foam material on microwave absorption is explored using experiment and simulation.We find that the foam structure of SiC/C foam material causes diffraction,multiple reflections,improves the interfacial polarization,and compatibilization.The absorption performance of SiC/C foam material is also studied.The-10 dB effective absorption bandwidth can be adjusted from 4.0 GHz to 18 GHz by tuning SiC/C foam material thickness to 3-7 mm.Therefore,the foam structure design is an effective way to improve the absorption performance of the SiC/C foam material. 相似文献