GH4169合金均匀化过程中相变动态原位研究

为揭示GH4169合金在均匀化处理过程中成分和组织的演变规律,利用高温金相显微镜实时原位观察热处理过程中合金的显微组织,定量分析了冷却后合金中Laves相的粒度分布,用电子探针EPMA探讨了合金中Nb元素在热处理前后的分布规律。结果表明,GH4169合金升温到1151℃时,邻近Laves相周围区域开始初熔。1180℃热处理后GH4169合金中Laves相颗粒数增加,但Laves相最大颗粒尺寸显著减小,小颗粒Laves相比例略有增加。在1180℃保温时,GH4169合金中已有液相存在,但NbC未溶解。热处理后合金中原枝晶间黑色区域的Nb元素偏析仍存在,但Nb元素在枝晶轴γ相中分布更加均匀。     

Nb含量对GH4169合金钢锭凝固及均匀化过程相演化规律的影响

以不同Nb含量的直径160 mm GH4169合金钢锭为研究对象,利用热力学软件Thermo-Calc的模拟计算及电子探针成分分析,系统研究了Nb元素含量变化对GH4169合金钢锭凝固及均匀化过程相演化规律的影响。结果表明:Nb元素含量的增加会降低合金初熔点和终熔点,扩大凝固区间,增加偏析形成的趋势;Nb元素含量的增加还可以提高GH4169合金钢锭凝固过程Laves相的析出温度,若Nb元素偏析浓度超过7.0%,Laves相的析出温度会高于标准均匀化温度1160℃,导致部分高浓度下生成的Laves相无法回溶。进一步的凝固过程中各相Gibbs自由能变化规律分析表明,GH4169合金凝固过程中,当达到Laves相的析出温度后,Laves相的形成激活能要显著小于MC碳化物,此时高浓度的Nb元素主要用于Laves相的析出和生长,Laves相的大量形成抑制了MC碳化物的进一步形成和长大,导致了Laves相与MC碳化物集合体的产生。上述的热力学分析结果与实际钢锭的相析出回溶实验结果一致。     

Nb含量对GH4169合金钢锭偏析规律的影响

利用光镜、扫描电镜和能谱仪等手段分析了不同Nb元素含量的GH4169合金钢锭组织特点及元素偏析规律,并对经单阶段均匀化热处理后钢锭的组织及残留析出相特征进行分析.结果表明:随着Nb元素含量增加,GH4169合金铸锭由边缘到心部,枝晶组织粗化,二次枝晶间距增大,Nb、Ti元素的偏析系数亦增大;经1160℃保温20h的均匀化处理后,Nb添加量越多,未回溶的析出相残留越多,且残留析出相有很明显的聚集趋势,残留析出物聚合体主要为富Nb的Laves相及富Nb、Ti元素的碳化物.不同Nb元素含量钢锭中Laves相完全回溶需要的时间应不相同,在高Nb含量条件下,传统的均匀化工艺无法使Laves相完全回溶;若同时考虑钢锭的尺寸因素,高Nb含量条件下,残留析出相的聚合体可能会演化为“黑斑”缺陷而使钢锭报废.     

激光增材制造高Nb含量GH4169合金微观偏析行为研究

目的减轻不同热处理状态下激光增材制造高Nb含量GH4169合金组织中的微观偏析。方法采用激光增材制造方法对球磨Nb合金化后的合金粉末进行快速成形,获得具有较高Nb含量的GH4169合金试样。通过光学显微镜、扫描电子显微镜及能谱分析、维氏硬度测试方法,对沉积态、固溶态和直接时效态试样进行分析,研究因合金中Nb含量变化引起的微观偏析对沉积态和热处理态合金的枝晶组织和显微硬度的影响。结果随着Nb含量的增加,一方面,由于枝晶间的Nb含量增加,枝晶间(γ+Laves)共晶数量增加,且共晶组织形貌更为连续;沉积态试样的显微硬度由228.4HV增大至534.1HV。另一方面,枝晶干Nb元素含量增加,枝晶干与枝晶间Nb元素含量的差异缩小,Nb元素的偏析比由8.59减小至4.13。后续固溶处理后,枝晶结构逐渐消失,枝晶间Laves相的数量随之减少,枝晶干与枝晶间的微观偏析减轻;固溶态试样硬度值随之减小,减小趋势随固溶温度的升高而逐渐平缓。随着Nb含量的增加,直接时效处理后,各试样显微硬度值在微观区域内的均匀性提高,枝晶干与枝晶间强化相的析出差异减小。结论合适的热处理制度既可以实现合金元素的均匀化,还能减小枝晶干与枝晶间强化相的析出差异,减轻激光增材制造高Nb含量GH4169合金组织中的微观偏析。     

熔体过热处理工艺对GH4169合金组织和力学性能的影响

选用光学显微镜、扫描电镜和电子万能试验机研究了不同熔体过热处理对GH4169合金组织和力学性能的影响。结果表明:熔体过热处理后,合金组织形貌规整,γ+Laves共晶团、有害Laves相析出数量减少,分布均匀;合金室温综合力学性能显著提高,存在最佳过热温度,此时Rm最大值为721 MPa,约是过热处理前的1.5倍;GH4169合金的硬度降低,存在最小值为10.15HRC,与过热处理前相比,降低26.7%;Nb、Mo元素偏析显著降低。     

激光增材制造Nb合金化GH4169合金组织分析

采用球磨合金化的方式,在常规GH4169合金粉末中添加Nb元素,利用激光增材制造技术成形了具有不同Nb含量的GH4169试样,研究了Nb含量对激光增材制造GH4169合金组织的影响。结果表明：激光增材制造Nb合金化GH4169合金显微晶粒结构仍为粗大柱状晶组织;随着Nb含量的增加,合金粉末在熔池中合金化反应放热量增多,使得柱状晶的生长方向由偏离激光束中心向外生长逐渐变化为朝向激光束中心向内生长。由于熔池中溶质浓度和粉末熔化放热量的增加,使得枝晶间γ+Laves共晶组织的数量增多,逐渐形成连续网状的共晶组织;DSC分析结果发现,随着Nb元素添加量的增加,共晶Laves相的初熔点升高,枝晶干γ相的熔点略有降低。另外,合金化改变了初生γ相的成分,枝晶干Nb元素含量最高浓度达到7.5wt.%,合金固溶强化作用得到加强。     

磷硼复合添加对GH4169合金均匀化的影响

利用微观组织分析手段、差示扫描量热法和布氏硬度研究了复合添加适量磷、硼对GH4169合金铸态组织和均匀化的影响。结果表明:GH4169合金中磷、硼的复合添加促进Nb、Ti的偏析和块状Laves相的形成。适量的磷、硼导致GH4169合金的初熔温度下降40℃,相应的均匀化温度选择在1120℃而不是通常的1160℃。均匀化处理可有效消除Laves相和显微偏析,硬度测试表明磷、硼有可能阻碍合金元素的扩散,均匀化时间有所延长。     

超塑成形对GH4169合金激光焊接组织的影响

采用激光连接/超塑成形组合技术制造了GH4169合金三层板结构件,研究了超塑成形(温度965℃,成形时间130min)对GH4169高温合金激光焊接组织的影响.试验结果表明:GH4169高温合金激光焊接组织主要由树枝晶构成,枝晶间中有Nb元素偏聚现象,即形成了一种金属间化合物Laves相;焊接组织在超塑成形后,焊缝中心出现了粗大的等轴晶粒,熔合线附近的柱状晶粒变得粗大,成形后大部分Laves相转变为δ相,但仍有少部分Laves相保留了下来;成形后焊缝的维氏硬度明显提高,由成形前的331.63HV0.1提高到391.74HV0.1,接近成形后母材的硬度415.63.超塑成形对GH4169高温合金激光焊接组织有明显的改善作用.     

均匀化温度对K4169合金显微组织和持久性能的影响

研究了两种均匀化温度下的热处理对K4169合金显微组织、Nb偏析和持久性能的影响。结果表明,随着均匀化温度的提高,合金中Laves的体积分数逐渐降低。1120℃时,Nb元素仍强烈偏析于枝晶间;当温度升高至1160℃时,Nb元素的偏析程度得到显著改善。经固溶和时效处理后,δ相分别主要以魏氏组织和颗粒状析出,1160℃处理试样中γ′′相的体积分数较大。650℃/620 MPa持久性能测试结果表明,持久寿命随均匀化温度的提高显著增加,但延伸率有所降低。持久断裂类型由穿晶韧性断裂变为沿晶-穿晶复合脆性断裂。     

冷却速率对GH4169合金铸态组织和力学性能的影响

通过水冷铜坩埚熔炼吸铸制备了不同直径的GH4169高温合金圆柱试样,采用金相显微镜(OM)和扫描电子显微镜(SEM)及X射线衍射(XRD)等对其凝固组织和析出相进行了分析,研究冷却速率对GH4169合金铸态组织和力学性能的影响规律。结果表明,随着冷却速率的增加,合金二次枝晶臂间距减小,凝固枝晶组织明显细化;Laves相尺寸减小且呈现弥散分布;Nb和Mo元素的偏析减轻;合金硬度和强度提高。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.