纤维预热温度对3D-C_f/Al复合材料显微组织及力学性能的影响

采用真空气压浸渗法制备纤维体积分数为51%的三维五向编织M40碳纤维增强铝基复合材料(3D-C_f/Al),研究纤维预热温度对3D-C_f/Al复合材料显微组织与力学性能的影响,并对比研究3D-C_f/Al复合材料与单向连续C_f/Al复合材料的差异。结果表明:复合材料致密度随着编织体预热温度的提高而增大,提高预热温度可有效减少复合材料内部孔洞和纤维偏聚等浸渗缺陷;复合材料的拉伸强度随纤维预制体预热温度的提高而显著降低。其中,在预热温度500℃、浸渗温度720℃、浸渗压力7 MPa和保压时间20 min的工艺条件下,所制备的3D-C_f/Al复合材料致密度为97.3%,拉伸强度为777.8 MPa,弹性模量为186.1 GPa。     

低浸渗压力制备纤维增强铝基复合材料

利用液态浸渗技术制备了氧化铝纤维增强铝基复合材料。研究结果表明,在低压下使液态合金浸渗纤维预制件制备铝基复合材料是可行的。在浸渗过程中,液态合金的温度对浸渗压力有较大影响。所制备的复合材料具有均匀的显微组织,基体中的共晶组织可依附在纤维表面形核生长。     

纤维预热温度对真空气压浸渗连续SiC_f/Al复合材料致密度和力学性能的影响

选用先驱体法制备的直径10~15μm束丝SiC纤维作为增强体材料,采用真空气压浸渗法制备了SiCf体积分数为40%的连续SiCf/Al复合材料,研究纤维预热温度对复合材料显微组织与力学性能的影响。结果表明:复合材料中原局部存在少量团聚的SiC纤维束随着纤维预热温度的提高,纤维团聚减少,分布更趋于均匀;而复合材料致密度和抗拉强度随纤维预热温度的升高先逐渐增加后缓慢降低;其中,在纤维预热温度为500℃、浸渗温度为730℃、浸渗压力为7 MPa和保压时间为5 min的浸渗工艺条件下所制备的连续SiCf/Al复合材料的致密度为97.24%,抗拉强度达到768.9 MPa。     

液态金属浸渗动力学模型及其应用

从流体动力学出发导出了液态金属浸渗纤维预制件的动力学模型.实验研究了碳纤维增强铝基复合材料的浸渗过程,测定了浸渗速度和浸渗系数.结果表明:实验数据与浸渗模型吻合;还发现了两种不同的浸渗方式,均匀浸渗和非均匀浸渗;并提出一种复合材料制造新工艺.用此工艺在不润湿的情况下,在低压力下制出高质量的C/Al复合材料。     

石墨颗粒铝基复合材料的研制

用预成形压力浸渗技术制备了石墨颗粒铝基复合材料，研究了石墨颗粒预成形的制备及压力浸渗时铝液温度、保温时间和石墨颗粒尺寸对复合材料制备的影响，测定了石墨颗粒铝基复合材料磨损特性。     

3D-C_f/Al复合材料真空气压浸渗工艺研究

三维编织碳纤维增强铝基复合材料(3D-Cf/Al复合材料)具有耐冲击、不分层、抗开裂、耐疲劳、整体性强等优点,但浸渗过程中存在难以浸渗和过度界面反应等问题。在采用真空气压浸渗制备单向排布Cf/Al复合材料的工艺试验基础上,进行了三维五向编织Cf/Al复合材料的真空气压浸渗工艺研究,得到了3D-Cf/Al复合材料真空气压浸渗成形工艺参数。在预热温度为500~550℃、浸渗温度为730℃、保压时间为20min时,制备出的3D-Cf/Al复合材料浸渗良好,其致密度达到95.88%,抗拉强度达到782.33 MPa。     

气压浸渗法制备Al2O3短纤维增强铝基复合材料

利用自行设计的试验装置采用气压浸渗法成功制备出Al2O3短纤维增强铝基复合材料,对金相组织和硬度进行了分析,得出了温度、体积分数、压力对浸渗的影响结果.证明了气压制备短纤维铝基复合材料的可行性.     

铜/铝固-液复合研究

利用压力条件下固-液复合法,在不同的铝液浇注温度下制备铜/铝复合材料,并对复合界面的结合性能和组织结构进行了研究。结果表明:在铜板预热温度400℃、单位压力1 000 MPa等其他条件相同的前提下,铝液浇注温度720℃时制备出的铜/铝复合材料抗拉强度最大,约为40.07 MPa;冶金复合界面层内部又分为不同的内层,且随着浇注温度的升高,内层数增加;沿着铝基体到铜基体的方向界面层各内层相分别为α-Al+CuAl2、CuAl2、CuAl,且各内层厚度逐渐减薄;拉伸断裂易发生在含CuAl2的层。     

压铸工艺生产的铝基复合材料的组织和性能

报道了压铸浸渗法生产的γ Al2 O3 长纤维、δ Al2 O3 短纤维和SiC颗粒强化铝基复合材料的组织特征和强度性能检测结果。试验结果表明 ,采用优化工艺条件 ,在工业压铸机上可以生产出高浸渗质量、可热处理的铝基复合材料。所获复合材料与 13 0MPa挤压浸渗生产的复合材料相仿 ,具有理想的工艺质量和组织结构 ,强度性能达到或超过混合律的预测值。     

真空吸渗挤压制备2D-C_f/Al复合材料的组织和性能研究

采用真空吸渗挤压工艺制备了二维碳纤维增强铝基(2D-Cf/Al)复合材料。在挤压力(比压)为60~90 MPa、真空度为10~30 k Pa、浸渗挤压温度为580~620℃、保压时间为60~120 s时,可以获得浸渗充分和成形质量良好的复合材料。微观组织观察分析表明,基体合金和碳纤维分布均匀,纤维无折断、漂移现象,无明显微观缺陷。对Cf/Al复合材料进行密度和拉伸性能测试,其密度比基体合金降低17.9%,抗拉强度提高100%。热处理实验表明,经过T6热处理,基体合金的组织得到改善,内部应力和缺陷得到有效控制和消除,抗拉强度提高41%,而碳纤维和基体合金热膨胀系数的差异会在复合材料内部产生不良应力,导致其拉伸性能没有提高反而下降16%。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

FORMULAS OF TENSION OF CONTINUOUS ROLLING PROCESS

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.     

RHEOLOGY FEATURE OF SIMPLE METAL MELT

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.