单晶高温合金再结晶形核条件及长大机制

对DD6单晶高温合金进行表面压痕处理,然后在不同温度(1220、1270和1310℃)热处理2h,研究合金再结晶的形核和长大行为.结果表明:γ'相溶解是再结晶的必要条件;再结晶晶粒以外,产生大量的亚晶界,离压痕中心越近,亚晶界密度越大,亚晶聚合粗化是再结晶的形核和长大机制.在γ'相溶解温度以上,γ'相对再结晶的形核和长大无明显影响.     

挤压工艺参数对FGH96合金棒材显微组织的影响

对FGH96合金进行了不同挤压工艺参数的热挤压变形,研究了挤压温度、挤压比、挤压速度对FGH96合金热挤压棒材的晶粒组织和γ′相的影响,以及γ′相对再结晶晶粒长大的影响。结果表明:在实验选定的挤压工艺参数范围内,FGH96合金均发生了动态再结晶,随着挤压温度的升高,再结晶晶粒尺寸增大;在FGH96合金棒材的显微组织中,大尺寸γ′相呈链状分布于晶界,小尺寸的γ′相弥散分布在晶粒内部;随着挤压温度的升高,晶界处的大尺寸γ′相逐渐溶解,晶界迁移、阻力减小,再结晶晶粒长大,挤压温度为1100℃时,晶界处的大尺寸γ′相开始快速溶解,再结晶晶粒开始明显长大;挤压比和挤压速度的影响主要体现在单位时间内等效应变量和变形潜热对再结晶形核和长大的双重作用上,挤压比或者挤压速度过大或过小均会出现不均匀组织。     

DD6单晶高温合金再结晶形核位置和机制研究

采用压痕变形方法,利用扫描电镜研究了DD6单晶高温合金在不同温度和状态下的再结晶形核位置及形核机理。结果表明,在低于γ′相溶解温度(≤1 220℃)进行热处理,胞状再结晶可以在碳化物、显微疏松、共晶处形核,1 220℃热处理等轴状再结晶可在表面形核,形成表面再结晶层。在1 270℃热处理时除了第二相形核外,再结晶主要在枝晶干上形核,形成了枝晶状再结晶,再结晶形核的主要机制为亚晶聚合形核机制。     

热挤压态FGH95合金的动态再结晶机制研究

针对热挤压态FGH95合金进行变形温度为1050~1120 ℃、变形量为50%和70%、应变速率为10?4~1 s?1的热压缩试验,研究该合金动态再结晶（DRX）的组织演变和形核机制。结果表明:提高变形温度和降低应变速率可以促进小角度晶界向大角度晶界迁移,有利于动态再结晶晶粒的长大;变形温度和变形量对热挤压态FGH95合金的动态再结晶机理的影响不明显,而应变速率对动态再结晶机制影响较大;随着应变速率的增加,热挤压态FGH95合金由不连续动态再结晶机制逐渐转变为连续动态再结晶机制;热挤压态FGH95合金的动态再结晶以不连续动态再结晶形核机制为主,以连续动态再结晶形核机制为辅;在1050 ℃、1 s?1变形条件下,热挤压态FGH95合金发生连续动态再结晶形核。     

FGH96合金静态再结晶行为的研究

研究了FGH96合金在再结晶退火中的静态再结晶行为，并对再结晶机理进行了讨论与分析。结果表明：在较大冷变形量下，FGH96合金的静态再结晶在很短时间内完成，再结晶组织中有大量的孪晶组织。冷变形造成γ’/γ，界面上的位错塞积，再结晶形核方式形核有亚晶粗化形核和应变诱导晶界移动（SIBM）方式。γ’相在应变诱发晶界迁移（SIBM）机制中起到两方面作用：一为冷变形在γ’/γ界面上形成高密度的位错塞积，这为晶界单向移动并为最终的再结晶形核提供驱动力，二是再结晶晶粒晶界的移动速度（即晶粒的长大）受到γ’相的分解速率控制。     

热处理对变形高铝Ni3Al基合金组织及性能的影响

对热变形量56％的高铝Ni3Al基合金在热处理过程中的组织转变进行了研究.结果表明:热处理过程中随β-NiA1相的增大,γ+γ′相区不断向β+γ′相区扩展,借此消除锻后形成的γ′脆性晶界,提高锻后合金的塑性.在γ+γ′两相区,γ′相不断发生回溶;而在β+γ′两相区,随着M23C6向MCⅡ碳化物逆转变的进行,γ相以MCⅡ为形核质点发生再结晶长大.此外于扩大的γ相内有呈方形的粒状γ′相析出,与γ相保持完全共格,可提高合金高温强度.     

Ni3Al基单晶合金IC6sx的表面再结晶

对Ni3Al基单晶合金IC6sx的表面进行吹砂变形处理;再在800-1260 ℃热暴露1-10 h,采用OM,SEM和EPM研究了IC6sx合金的再结晶行为.结果表明,合金再结晶开始形核的温度约1000 ℃,一次再结晶完成的温度为1200-1210 ℃.在1200-1240 ℃热暴露时的再结晶层厚度约为10 μm,而在1260 ℃热暴露时增长到约23 μm.再结晶在枝晶干长大的速度明显小于枝晶间,再结晶层和基体的枝晶干之间观察到一种由粗大条状γ′相和γ γ′相构成的胞状转变结构,这是由于枝晶干中粗大的γ′相阻碍再结晶向基体内生长形成的.     

镍基单晶高温合金的动态再结晶(英文)

利用高温蠕变试验,研究SRR99单晶高温合金在低应变速率下的动态再结晶行为。结果显示,在大气环境且无涂层保护的情况下,长时间高温低应力作用会使单晶合金发生动态再结晶,动态再结晶的温度和临界应变量均低于静态再结晶,再结晶晶粒均位于试样边缘的γ′相贫化层内,再结晶深度较浅,一般不超过15μm。在高温低应变速率下,再结晶以完整晶粒的形式发生,晶粒内无条状γ′相存在。单晶合金在高温低应变速率下的动态再结晶行为主要与高温氧化有关。在实际服役条件下,表面涂层可有效抑制动态再结晶的发生。此外,还利用高温压缩试验,研究了SRR99单晶合金在高应变速率下的动态再结晶行为。在高应变速率下,单晶合金发生动态再结晶的温度和临界应变量均显著提高,再结晶以胞状组织的形式发生,晶胞内含有大量粗大的条状γ′相。     

变形参数对挤压态AZ41M镁合金热变形行为和组织演变的影响

通过热模拟压缩试验研究了挤压态AZ41M镁合金在应变速率为0.005～1s-1、温度为300～450℃条件下的热变形行为.利用光学显微镜分析了合金热变形过程中的组织演变.结果表明:挤压态AZ41M镁合金热变形过程中,真应力应变曲线表现出典型的单峰动态再结晶(DRX)特征,合金具有比较高的温度和应变速率敏感性;合金热变形过程中,DRX 会促进晶粒细化,且应变速率越小,温度越高,合金越容易发生动态再结晶;温度的升高可以促进合金DRX 的发生与晶粒长大,能改善合金变形的不均匀性,但温度过高会导致晶粒尺寸粗大不均匀;应变速率越大,变形量越大,晶粒尺寸越细小且更均匀;合金热变形过程中,DRX形核机制主要受温度影响,应变速率与变形量对其影响较小,在温度较低(300℃)时,合金主要以弓弯形核机制发生不连续动态再结晶,在较高温度(450℃)时,同时存在弓弯形核不连续动态再结晶形式和孪晶诱变形核连续动态再结晶形式.     

某新型粉末高温合金的晶粒细化

运用Gleeble-1500热模拟机,对热等静压态的某新型粉末高温合金进行了形变温度在1120～1170℃和应变速率在2×10-3～2×10-1s-1下的热压缩实验研究。实验结果表明:热压缩过程发生了动态再结晶,形变温度和应变速率对动态再结晶细化晶粒有重要影响;在高应变速率、低于γ′相完全固溶温度下可获得动态再结晶细晶组织;在高于γ′相完全固溶温度下再结晶晶粒尺寸粗化;其动态再结晶晶粒平均尺寸与Zener-Hollomon参数呈双对数线性关系。     

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.