磁控溅射制备钛合金扩散焊中间层Ti薄膜的研究

以磁控溅射的Ti薄膜作为中间层可在较低温发下实现钛合金的扩散焊.研究了工作气压和溅射功率两个主要工艺参数对Ti薄膜沉积速率、成膜质量的影响规律.在Ar气压为0.8Pa,溅射功率为38W的条件下在TC4试祥表面沉积了厚约1μm的Ti薄膜,采用感应加热方式将其分别快速加热至600℃,800℃,900℃和1000C.通过对薄膜表面形貌、成分及物相分析发现,随着加热温度的升高,薄膜晶粒显著长大,少量Al,V原子扩散进入Ti薄膜中,除Ti6O外未发现新的物相.     

以Ti,Ni薄膜为中间层的钛合金与高温合金低温扩散焊研究

采用磁控溅射技术在TA15钛合金表面沉积Ti薄膜,在DD6单晶高温合金表面沉积Ni薄膜,以Ti,Ni薄膜作为中间层进行低温扩散焊研究.通过X射线衍射分析发现Ti,Ni薄膜均为多晶体结构.采用AFM分析发现,沉积薄膜后,TA15钛合金和DD6单晶基片的表面粗糙度均有所降低.以Ti,Ni薄膜作为中间层在800℃/20MPa/2h规范下实现了TA15钛合金和DD6单晶高温合金的异种材料低温扩散连接.通过扫描电镜和能谱分析表明,Ti,Ni两元素均扩散至另一母材界面,整个接头呈现分层组织,主要为Ti2Ni和TiNi相.     

脉冲电沉积纳米晶Ni-Co合金镀层热稳定性的研究

采用X射线衍射(XRD)、能谱分析(EDS)等方法研究脉冲电沉积法制备的纳米晶Ni-Co合金镀层的组织结构和合金成分.测定不同退火温度下纳米晶Ni-Co合金镀层的显微硬度,并着重研究Ni-23.5%Co(质量分数)合金的热稳定性,结果表明:随着退火温度的升高,纳米晶Ni-Co合金在低温退火后显微硬度有所升高,在250℃时达到最高值,然后随退火温度的继续升高而降低.纳米晶Ni-23.5%Co合金镀层的晶粒尺寸逐渐增大,从原始晶粒尺寸13.5nm长大到300℃时的98.5nm,在升温速率为20K·min-1的DSC曲线中,Ni-23.5%Co合金在约300～350℃一直是低能放热,随后出现明显的放热峰,其峰值温度为372℃,放热焓为14.22J·g-1.通过测定不同升温速率条件下的DSC曲线峰值温度,由Kissinger方程求得纳米晶Ni-23.5%Co合金镀层的晶粒长大激活能为212.SkJ/mol.     

表面纳米化对高温Ti合金与TiAl合金的扩散连接工艺及力学性能影响

目的研究表面纳米化Ti合金与Ti Al合金异质扩散连接的界面反应、力学性能和工艺条件。方法利用高能喷丸技术对钛合金的表面进行纳米化处理,然后在高温压力真空炉内进行扩散连接实验。结果 Ti合金/Ti Al扩散连接的结合强度与中间层厚度密切相关,当中间层厚度为1.7~2.0μm时,剪切强度最大。结论表面纳米化可以促进原子扩散、增加接头厚度、缩短扩散连接所需的时间。对于扩散界面存在缝隙接头,在无压热处理条下表面纳米化样品可以快速提高焊合率,改善连接质量。     

Inconel718合金扩散连接接头的组织与性能研究

对细晶Incone1718高温合金无中间层和加Ni箔中间层两种情况下的扩散连接进行了研究,分析了不同的连接温度、连接压力、连接时间等工艺参数对接头剪切强度的影响;通过SEM、EPMA和金相技术对接头微观组织和力学性能进行了分析.确定了获得优质接头的最佳工艺参数区间,即扩散连接温度T=1 050℃,连接压力P=20 MPa,连接时间t=45 min,选用Ni箔作为中间层,厚度为25 μm.     

稀土Ce含量对双脉冲电沉积Ni-Co合金层结构及耐蚀性的影响

目前将稀土用作电沉积Ni-Co合金添加剂时有关其对镀层耐蚀性的影响报道较少.通过X射线衍射、极化曲线和中性盐雾试验研究了稀土Ce对双脉冲电沉积纳米Ni-Co合金层晶粒尺寸及耐蚀性的影响,采用扫描电镜对有无稀土Ce的Ni-Co合金镀层盐雾腐蚀前后的表面形貌进行了观察.结果表明:无论是否添加稀土Ce,Ni-Co合金镀层均为面心立方结构,主要的晶面取向为(111)和(200)面;稀土Ce含量在一定范围时,细化了Ni-Co合金镀层的晶粒,镀层的自腐蚀电位正移,自腐蚀电流减小,耐蚀性增加,且加入量为0.6 g/L时晶粒尺寸最小.     

焊后热处理对高氧TC4/TC17钛合金线性摩擦焊接头组织及性能的影响

对高氧TC4/TC17钛合金线性摩擦焊接头进行热处理,研究了不同热处理温度对异质钛合金线性摩擦焊接头显微组织及力学性能的影响.结果表明:异质钛合金线性摩擦焊接头焊缝区在TC17侧形成亚稳定β相,在高氧TC4侧形成针状马氏体相.经过热处理后,板条状α相在晶界处析出,针状α相在晶粒内部析出,并且残余α相在保温过程中发生分解,随着热处理温度的升高,析出相逐渐长大.接头焊缝及热力影响区显微硬度在热处理后显著增加.裂纹尖端张开位移(Crack tip opening displacement,CTOD)试验结果表明:接头断裂韧性薄弱区域在焊缝区及TC17侧热力影响区,热处理温度的升高可以明显提高接头薄弱区域的断裂韧性.     

DD3单晶合金短时液相扩散连接接头组织与性能研究

采用D1P和D1F两种中间层合金在1250℃下分别保温10,30min,1,2,4h扩散连接DD3单晶合金.这两种中间层合金是在DD3合金成分基础上添加了一定量的降熔元素硼,分别以粉和箔带形式使用.对上述规范下获得的DD3接头组织和性能进行了研究分析,结果表明, 扩散时间短,D1P中间层合金扩散焊接头组织很不均匀,在中间层合金流入处生成大量光板γ′相,对接头持久性能不利,1250℃下扩散4h接头的980℃持久性能为母材性能的60%;而D1F中间层合金扩散焊接头组织均匀一致,1250℃下扩散4h接头980℃持久性能超过母材性能的70%.     

Ti2AlNb合金与钛基复合材料的低温固相扩散连接机理

Ti2AlNb合金和Ti基复合材料可以使用直接固相扩散的方法进行连接,但较高的扩散温度使得母材发生相变,其接头性能也因此变差。采用Ti箔中间层的方法优化Ti2AlNb合金和Ti基复合材料的固相扩散连接接头性能。结果表明:加入30μm的Ti箔中间层后,扩散连接温度由950℃降低至850℃,变形率由5%降低至1.7%,扩散连接温度的降低有效地改变了接头界面的组织,典型界面组织为Ti2AlNb/富B2相/α+β双相组织/Ti基复合材料,其中接头界面处α+β双相组织的形成提高了接头的强度。最佳扩散连接工艺参数为850℃/60min/5 MPa时,剪切强度达到最大值399MPa,实现了Ti2AlNb和Ti基复合材料在低温下的扩散连接。     

钛合金化学镀镍-磷前后处理对镀层耐蚀性能的影响

为了提高TC4钛合金化学镀镍-磷层的耐腐蚀性能,对TC4基材化学镀前作微弧氧化处理和化学镀后作低温热处理,采用中性盐雾法研究了其腐蚀性能。结果表明:TC4钛合金表面微弧氧化、化学镀镍-磷后作再热处理,镀层的耐蚀性能最好,达8级;直接化学镀后再热处理镀层的耐腐蚀性为5级,不经热处理镀层的耐蚀性能最差,仅为1级;微弧氧化和低温热处理均能大大提高化学镀镍-磷层的耐腐蚀性能。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.