连续凝固偏晶合金薄带凝固组织进化过程模拟

分析了偏晶合金薄带垂直连续凝固过程,发展了描述该条件下偏晶合金凝固组织演变的数学模型,将计算的温度场和浓度场与凝固组织演变的控制方程相耦合,模拟了Al-5Pb(质量分数．%)合金的凝固过程．结果表明．在固/液界面前存在一过冷区、弥散相液滴在此区间内形核,这些液滴在移向凝固界面的过程中进行扩散长大,随着凝固速度的提高,形核率升高,弥散相液滴的数量密度增大．平均半径减小。     

连续凝固偏金合金薄带凝固组织进化过程模拟

分析了偏晶合金薄带垂直连续凝固过程。发展了描述该条件下偏晶合金凝固组织演变的数学模型。将计算的温度场和浓度场与凝固组织演变的控制方程相耦合，模拟了Al-5Pb(质量分数.%)合金的凝固过程。结果表明，在固／液界面前存在一过冷区，弥散相液滴在此区间内形核。这些液滴在移向凝固界面的过程中进行扩散长大。随着凝固速度的提高。形核率升高。弥散相液滴的数量密度增大，平均半径减小。     

难混溶合金及其制备技术研究进展

综述了难混溶合金在微重力和地面条件下制取具有均匀弥散相结构的研究成果。指出了形核、生长-扩散-对流／扩散、重力造成的沉积或上浮、相间界面能、Ostwald熟化、Marangoni运动、Brownian凝并、第二相含量和冷却速度等影响难混溶合金凝固的各种因素，分析了难混溶合金在定向凝固过程中从纤维型规则复合组织到规则排列的串状组织再到弥散分布粒子的组织演变现象。根据难混溶合金的凝固特点，介绍了粉末冶金法、定向凝固法、模拟微重力熔融铸造法、搅拌铸造法、快速凝固法等几种不同特点的制备技术。总结了密度动态法、分离粒子法、相场法等计算机组织模拟方法在难混溶合金方面的应用，同时指出了难混溶合金研究存在的问题和今后的研究方向。     

高温度梯度下Al-In偏晶合金定向凝固组织的演化规律

应用高温度梯度的方法，研究了在定向凝固条件下温度梯度与凝固速率的比值G／R对Al-17．5％In(质量分数)合金凝固组织的影响．结果表明，偏晶合金的定向凝固与共晶合金定向凝固的生长规律类似．在高温度梯度下，仅在很低的生长速度时才能形成二相有序排列的共生．在偏晶合金定向凝固进入稳态生长以后，在各自的相凝固前沿富集了另一相的溶质，由于两相的层间距不大，长大过程中的横向扩散占主导地位．随着生长速度的增大或温度梯度的降低，Al-17．5％In合金定向凝固组织从纤维结构到周期性或规则排列的串状结构再到弥散分布结构转变．这种转变与固一’液界面形状的转变有密切关系．     

偏晶系Al-Bi合金的自生复合行为

在定向凝固条件下,研究了偏晶系Al-Bi合金的自生复合行为,考察了凝固速度和温度梯度对其自生复合行为的影响。试验结果表明偏晶反应可以生成两相有序排列的共生组织。在一定的温度梯度下,随着凝固速度的提高,组织由规则形态的纤维(或串状)组织向弥散分布的不规则组织转变。当G／V＞1．60×109K·s／2时,能得到规则的组织;反之,则得到不规则的弥散分布的组织,纤维间距与凝固速度的关系满足λ2V=C。     

Ti-5.8Al-4.8Sn-2Zr-1Mo-0.35Si-0.70Nd合金中富钕稀土相研究

针对Ti-5.8Al-4.8Sn-2Zr-1Mo-0.35Si-0.70Nd粉末冶金高温钛合金中富钕稀土相的形成、尺寸、分布、形态、长大及结构特征进行了系统研究。结果表明:快速凝固态高温钛合金粉末中稀土相为液态析出相,其尺寸大部分在50~250 nm之间,弥散分布在基体中;晶内稀土相多为球状,晶界稀土相多为椭球状,其长轴平行于晶界;TEM观察到的稀土相的尺寸和分布与理论计算相符合;快速凝固高温钛合金粉末经过700~1000℃/110 MPa/0.5 h热等静压成形后,快速凝固过程中已析出的稀土相尺寸变化不大;同时细小的稀土相从过饱和的基体中大量固相析出;经过1200℃/140 MPa/3 h热等静压成形后,稀土相颗粒尺寸大部分在150~500 nm之间,有明显长大;稀土相的高分辨图像及同心衍射环花样表明,快速凝固高温钛合金粉末中的稀土相由5~10 nm的纳米晶组成,经过1200℃热等静压成形处理后的稀土相仍由纳米晶组成,而且纳米晶的尺寸没有明显变化;但是稀土相的"基体"上明显出现富Sn元素的"第二相"颗粒,结构变得复杂。     

冷变形及时效处理对CuSn10Zn2FeCo合金组织性能的影响北大核心CSCD

利用XRD、SEM、TEM等测试分析手段,研究了冷变形及时效处理对Cu Sn10Zn2Fe Co合金组织性能的影响。结果表明：在冷变形量40%,400℃时效处理4 h条件下,合金试样抗拉强度和伸长率分别为635 MPa和19.5%。透射电镜观察显示合金基体中弥散分布着尺寸在10～50 nm不等的纳米强化相,纳米颗粒与基体界面关系良好。当冷变形量为60%时,析出相在时效过程中发生粗化现象,合金试样力学性能下降。     

冷变形及时效处理对CuSn10Zn2FeCo合金组织性能的影响

利用XRD、SEM、TEM等测试分析手段,研究了冷变形及时效处理对Cu Sn10Zn2Fe Co合金组织性能的影响。结果表明:在冷变形量40%,400℃时效处理4 h条件下,合金试样抗拉强度和伸长率分别为635 MPa和19.5%。透射电镜观察显示合金基体中弥散分布着尺寸在10~50 nm不等的纳米强化相,纳米颗粒与基体界面关系良好。当冷变形量为60%时,析出相在时效过程中发生粗化现象,合金试样力学性能下降。     

凝固速度对高温度梯度定向凝固Al-17.5In合金组织的影响

在高温度梯度下对Al-17.5In偏晶合金进行定向凝固,分析了其定向凝固组织形成机制,考察了不同凝固速度对Al-17.5In偏晶合金凝固组织的影响,获得了高温度梯度定向凝固条件下微观组织的演化规律,即在固定的高温度梯度下,随着抽拉速度的增大,第二相形态演化的过程依次为:规则的纤维状,发生颈缩的纺锤状,粗化的球状,均匀弥散分布于基体中。纤维间距随着凝固速度的增大而减小。     

中小型球铁件压边冒口的探讨

在实际生产中,球铁件经常使用压边冒口。由于压边宽度较窄,它在球铁件凝固的液态收缩阶段有一定的补缩能力,而在共晶结晶阶段压边处凝固,使铸件完全封闭而能充分利用其自身膨胀,对凝固末期的第二阶段收缩进行补缩,以获得健全铸件。因此压边冒口的补缩作用与中小球铁件的凝固——收缩特性相吻合。当然它也具有自身的一定特点:压边冒口没有明显的冒口颈,这对冒口——铸件补缩系统的冷却——凝固条件和铸型温度场的分布产生影响,给工艺设计带来了新因素。本文对压边冒口的大小、压边宽度、铸型及原材料条件和冒口设计进行讨论。试验是在生产条件下进行的。熔炼设备为2.5吨热风水冷冲天炉。出炉温度1380～1420℃。炉渣氧化铁含量<5％。采用稀土镁硅铁合金球化剂,球铁化学成份为(％):C3.7～3.9。终Si2.7～2.9,Mn<0.5,S<0.03,     

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.     

A Concordant Shift Model for Flow in Bulk Metallic Glasses

The homogeneous plastic flow in bulk metallic glasses(BMGs) must be elucidated by an appropriate atomistic mechanism. It is proposed that a so-called concordant shifting model, based on rearrangements of five-atom subclusters,can describe the plastic strain behaviour of BMGs in a temperature range from room temperature to the supercooled liquid region. To confirm the effectiveness of the atomic concordant shifting model, a comparative investigation between the vacancy/atom model and the concordant shifting model is carried out based on the estimation of the strain rate deduced from two models. Our findings suggest that the atomic concordant shifting model rather than the vacancy/atom exchange model can well predict the large strain rate in the superplasticity of BMGs.