熔体温度对类K445合金组织及硬度的影响

研究了真空熔炼时熔体温度对类K445镍基高温合金铸态组织及硬度的影响.结果表明,熔体温度对合金的相种类没有影响,均由树枝状y基体、弥散分布于基体的γ'相、晶界和枝晶间的γ γ'共晶、以及γ"、MC碳化物、少量M3B2硼化物等强化相组成;但随熔体温度的升高,枝晶逐渐细化,一次枝晶轴大量熔断;MC碳化物含量逐渐减少,γ γ'共晶和γ"相逐渐增多;同时,随熔体温度的升高,合金的硬度不断提高.在1600℃保温时,合金组织中枝晶最细小、γ γ'共晶和γ"含量最多、碳化物含量最少,且HB硬度达到最高值3.84 GPa.     

DD6单晶高温合金凝固特性研究

利用等温凝固淬火法、光学金相技术、定量金相技术以及扫描电镜、能谱分析等方法,研究了Re含量为2%的DD6单晶高温合金的凝固特性,结果表明,合金凝固过程中所析出相依次为γ相→MC相→共晶γ′→枝晶间γ′→枝晶干γ′,DD6合金的固-液相温度范围(ΔT)、有效结晶温度范围(ΔT2)和F值(枝晶间失去补缩能力温度下的液相体积分数)较小,铸造性能较好.     

铸态GH742合金的凝固特点及枝晶偏析

高合金化GH742合金存在严重的枝晶偏析,Nb、Ti大量偏聚于枝晶间,导致MC碳化物、(γ+γ′)共晶、Laves相、δ相等析出;高Mo含量及其枝晶间偏析是析出σ相的重要原因;La、Ce在枝晶间的富集促使含氧硫稀土相和Ni5Ce相的析出。与一般合金凝固特点不同,高含量Al、Ti、Nb导致GH742合金凝固过程中先后发生(γ+γ′)和(γ+Laves)两种类型的共晶反应。结合差热分析技术和凝固组织特点确定了合金的凝固温度区间为1346-1190℃,凝固顺序为γ、MC、(γ+γ′)、Laves、Ni5Ce。     

GH742y合金凝固偏析行为

采用组织分析和差热分析相结合的方法系统研究GH742y合金的凝固偏析行为和铸态组织形成规律。GH742y合金枝晶偏析严重,组织析出复杂:Cr、Co、W、V和Al偏析于枝晶干,而Nb、Ti和Mo等元素在枝晶间的富集导致一次和二次γ′相、(γ γ′)共晶、MC碳化物、M6C碳化物、Laves相和δ相的析出;稀土元素La和Ce的偏析导致Ni5Ce相和富氧硫稀土相的枝晶间析出。相分计算表明,严重的元素偏析以及大量富Nb和Ti相的析出是σ相和μ相等有害TCP相析出的主要原因。GH742y合金的凝固顺序为:γ基体、MC碳化物、一次γ′相、(γ γ′)共晶、Laves相、Ni5Ce相和M6C碳化物。     

钒对高铬白口铸铁凝固和显微组织的影响

论述了Fe-C-Cr-V合金的凝固特点,以及钒对该合金系显微组织的影响.当w（V）＜5%时,钒使合金的共晶点稍向右移;当w（V）＞5%时,钒使共晶点左移.w（V）量大于2%后,钒能抑制w（Cr）/w（C）＜5的Fe-C-Cr合金M3C的形成,得到M7C3型碳化物,含钒的Fe-C-Cr-V合金,由于VFe结晶后不久发生（γFe＋MC）共晶反应,缩短了γFe枝晶长大的温度范围,使γFe枝晶细化.指出了为得到MC体积量＞M7C3体积量的C、Cr、V含量适宜范围.     

一种新型高温合金凝固组织和元素偏析行为研究

采用热力学平衡模拟计算、差热分析(DTA)和等温凝固淬火试验(ISQ)相结合的方法对一种新型镍基高温合金K4750合金的凝固组织和主要元素的偏析行为进行研究。结果表明,实际K4750合金的固相线温度为1270℃,液相线温度为1350℃,MC型碳化物析出温度为1320℃;凝固顺序为L→γ(1350℃),L→γ+MC(1320℃)。K4750合金在凝固初期凝固速度较快,液相体积分数下降明显,凝固后期速度开始变慢,在1310～1290℃温度区间内枝晶间连通残余液相开始断开,同时会有大块状的MC相析出,进一步阻碍液相的连通,从而极易导致合金凝固疏松的形成。合金中W、Fe、Cr的溶质分配系数大于1,富集于枝晶干,为负偏析元素;Ti、Nb、C、Mo的溶质分配系数小于1,富集于枝晶间的液相中,为正偏析元素。     

熔体保温时间对类K445合金组织及硬度的影响

采用真空熔炼工艺制备类K445高温合金,研究熔炼保温时间对其铸态组织及硬度的影响。结果表明,熔体保温时间对合金的相种类没有影响,合金均由树枝状γ基体、弥散分布于基体的γ′相、枝晶间的γ＋γ′共晶、γ′′相、MC碳化物、少量M3B2硼化物等强化相组成;但随熔体保温时间的延长,枝晶尺寸先减小后增大,MC碳化物含量先减少后增多,γ＋γ′共晶和γ＇＇相含量先增多后减少;同时合金的硬度呈先升高后降低的趋势;保温30 min时枝晶最细小、γ＋γ′共晶和γ′′含量最多、MC碳化物含量最少,且平均硬度达到最高值HB381。     

GH2132高温合金熔敷金属结晶裂纹敏感性

针对GH2132高温合金熔敷金属热裂纹敏感性问题,通过采用试制焊丝、熔敷金属焊接试验、组织及断口分析、凝固计算等手段对熔敷金属组织、凝固行为、开裂机制等进行了研究. 结果表明,试验熔敷金属金相组织主要由柱状树枝晶γ相(NiCrFe固溶体)、枝晶间富Ti的Laves相(Cr,Fe,Ni)₂ (Ti,Mo)、MC碳化物与共晶组织组成,凝固路径为L→L + γ→L + γ + MC→L + γ + MC + Laves→γ + MC + Laves,裂纹断口呈典型的鹅卵石共晶花样,整个断口形貌被呈自由表面的液膜所覆盖,属于发生在高温段的结晶裂纹. 结晶裂纹开裂机理为在凝固过程的终了阶段,发生了L→γ + Laves的低熔点共晶反应,在凝固收缩应力作用下,残余液相未及时补充而形成. Laves相的形成主要与凝固过程中Ti元素的偏析有关,理论计算结果表明,GH2132结晶裂纹指数(solidification cracking index, SCI)值为1944 ℃,(solidification temperature range, STR)为258 ℃,在结晶裂纹敏感性评价方面,相比STR,SCI指标能相对更为合理地实现结晶裂纹敏感性的量化评价,但仍存在考虑因素不全等问题.     

镍基高温合金GH4282的凝固和偏析行为

采用差示扫描量热（DSC）分析、显微组织观察和热力学计算相结合的方法对镍基高温合金GH4282的凝固过程和元素偏析行为进行研究,得到了合金的凝固顺序以及元素偏析特征。结果表明,GH4282合金的凝固顺序为：γ基体、MC碳化物以及少量的硼化物。由DSC测得的合金GH4282合金的固-液相温度范围为1316~1367 ℃,MC、M6C型碳化物和γ′相的溶解温度分别为1338 ℃、1092 ℃和1003 ℃。热力学计算结果表明,GH4282合金在凝固过程C、B、Ti和Mo偏聚于枝晶间,Al偏析于枝晶干,Cr、Fe和Co几乎不发生偏析,这与铸态组织观察到的元素偏析特征是一致的。     

GH4151合金的凝固偏析行为及均匀化热处理研究

GH4151合金是一种承温能力高达800℃的新型涡轮盘用铸锻变形高温合金,该合金在凝固过程中元素偏析严重,主要偏析元素包括Nb、Mo和Ti等元素,同时合金中包含大量的C元素,在熔炼凝固后期由于残余液相中的元素富集,枝晶间会析出大量有害相,包括（γ-γ′）共晶,Laves相,η相和MC碳化物。实验通过研究C含量对各偏析元素的影响发现,增加C含量可减轻Nb元素在枝晶间的偏析,此外,随C含量的增加枝晶更发达,枝晶间区域减少。随后通过研究在1160～1210℃不同温度下的均匀化热处理对各枝晶间析出相的影响发现,（γ-γ′）共晶和Laves相的熔点约为1180℃,η相的熔点约为1200℃,MC碳化物的熔点超过1300℃;同时,发现1170℃/16 h+1200℃/8 h双步均匀化热处理不仅可以消除铸锭中的偏析,而且避免了低熔点相过烧而产生的孔洞,使坯料更加有利于后续开坯变形。     

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.     

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.     

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.