Al、Mn元素对Mg-2.5Sn-3.5Ca合金微观组织与力学性能的影响

目的 研究Mg-Sn-Ca-Al系合金的力学性能与微观组织之间的关系,以期开发一种新型的高性能、低成本的非稀土镁合金材料。方法 在非稀土Mg-2.5Sn-3.5Ca合金中添加Al和微量Mn元素,制备出了Mg-2.5Sn-3.5Ca-xAl合金（x=1,5;分别标注为TXA341,TXA345）以及Mg-2.5Sn-3.5Ca-5Al-0.5Mn合金（标注为TXAM3450）,并对其铸态、均匀化态以及挤压态合金的微观组织与力学性能进行系统研究。结果 TXA345合金兼备高的强度和优良的塑性,其屈服强度、抗拉强度和塑性分别为~340 MPa,~350 MPa,~9.6%;TXAM3450合金表现出更高的屈服强度（~360 MPa）和抗拉强度（~375 MPa）,但是其塑性仅有~3.5%;TXA341合金的屈服强度、抗拉强度和塑性分别为~215 MPa,~298 MPa,~4.3%。高Al含量的TXA345合金表现出较高屈服强度,是由于合金内部形成了高密度的G.P.区,并直接导致其再结晶晶粒可细化至~0.8 μm。继续在TXA345合金的基础上添加微量的Mn元素,TXAM3450合金内G.P.区的析出密度继续提高,并且会伴有条带状Al2Ca微米第二相的出现,因此其屈服强度进一步升高,然而该条带状微米相在室温下的塑性较差,因此直接导致TXAM3450合金低的伸长率。结论 相关结果对于设计高强塑兼备的非稀土变形镁合金具有较好的指导意义,为非稀土镁合金在结构材料中的广泛应用提供了可能。     

Al，Zn对挤压Mg-1Mn合金晶粒组织和塑性变形机制的影响

目的 探索镁合金中常用合金化元素Al,Zn对挤压Mg-1Mn合金的晶粒组织和力学性能的影响,为含Mn合金的成分设计及商业化应用提供理论支撑.方法 在280℃下,对Mg-1Mn,Mg-1Mn-1Al和Mg-1Mn-2Zn合金进行热挤压,制备镁合金棒材,采用拉伸测试分析力学性能,利用电子背散射衍射技术观察晶粒组织,并通过粘塑性自洽模型研究塑性变形机制.结果 在3种合金中,Mg-1Mn-1Al的晶粒最为细小,平均晶粒尺寸为1.3μm,屈服强度、抗拉强度和断裂伸长率分别为309 MPa,313 MPa和19.5％.结论 在Mg-1Mn合金中,与Zn相比,较低含量的Al具有更好的再结晶晶粒细化效果.Al,Zn的添加能够有效抑制基面滑移,促进非基面滑移的开启.     

挤压比对Mg-Zn-Y合金微观组织和力学性能的影响

研究了在350℃不同挤压比(16、32)下的Mg-6xZn-xY(x=0.5,0.75,1)合金微观组织和室温力学性能。结果表明,当挤压比为32时,合金中第二相体积百分含量较多,平均晶粒尺寸较小。其中,Mg-6Zn-1Y合金在挤压比为16时,α-Mg基体平均晶粒尺寸为14.6μm,抗拉强度及屈服强度分别为264MPa和169MPa;当挤压比为32时,α-Mg基体平均晶粒尺寸为5.9μm,抗拉强度和屈服强度达到337 MPa和237 MPa,分别提高了27.7%和40.3%。另外,所有合金经热挤压后都有良好的塑性,室温拉伸断口均呈韧性断裂特征。     

挤压态Mg–9Al–Zn–0.5RE–Ca–Si合金微观组织和力学性能

目的 改善AZ91镁合金在温度超过120℃时的力学性能。方法 在AZ91合金中添加Ca、Si和La/Ce混合稀土元素。在360℃下等温挤压,平均挤压速度为1.2 mm/s,挤压比为30︰1,以探究Ca、Si和La/Ce混合稀土元素对AZ91合金力学性能、物相组成和显微组织等的影响。结果 在AZ91挤压态合金中,与添加Si元素相比,Ca元素对挤压态合金的力学性能影响更大。在室温时,Mg–9Al–Zn–0.5RE–Si挤压态合金的屈服强度、极限抗拉强度和伸长率分别是254 MPa、306MPa、7.0%,而Mg–9Al–Zn–0.5RE–0.5Ca挤压态合金的屈服强度、极限抗拉强度和伸长率分别是308 MPa、330 Ma、7.1%。Mg–9Al–Zn–0.5RE–0.5Ca–0.5Si挤压态合金室温力学性能最佳,其屈服强度、极限抗拉强度和伸长率分别是351 MPa、383 MPa、7.4%,说明Ca、Si这2种元素的协同作用可同时提高室温下AZ91合金的强度和塑性。在150℃和200℃下,Mg–9Al–Zn–0.5RE–0.5Ca–0.5Si合金仍然具有最佳的力学性能。在150℃下,其屈...     

Sb变质Mg-10Al合金的组织与力学性能

研究了不同Sb含量的Mg-10Al合金的微观组织及在室温和150℃高温下的力学性能。结果表明,加入适量的Sb,Mg-10Al合金中生成了弥散分布的针状Mg3Sb2相,α-Mg初晶显著细化,抑制了网状共晶组织的形成。当Sb含量为0.5%(质量分数)时,组织细化效果最佳。随着Sb含量的增加,室温及高温下合金的抗拉强度、屈服强度和伸长率先升高后降低,均在Sb含量为0.5%(质量分数)时获得最佳综合性能。Mg-10Al-0.5Sb合金在150℃的抗拉强度为180MPa、伸长率为19%,比Mg-10Al合金分别提高了30%和90%。此外,在150℃条件下,含Sb合金仍保持了与其在室温下相当的强度,而未添加Sb的Mg-10Al合金的强度则明显下降。     

石墨烯增强镍基粉末高温合金复合材料的力学性能

采用湿混法将石墨烯纳米片分散到高温合金粉末中,并采用热等静压+热挤压+等温锻造+热处理的方法制备出FGH96镍基粉末高温合金。结果表明:石墨烯纳米片在高温合金中分散均匀,初步发现在后续的热工艺过程中并未发生变性;添加0.1%(质量分数)的石墨烯后,室温抗拉强度和屈服强度分别提高了58MPa和43MPa,塑性从21.0%提高到37.3%;650℃条件下抗拉强度和屈服强度分别提高了58MPa和28MPa,塑性从18.5%提高到26.5%。此外对石墨烯增强FGH96镍基高温合金力学性能的作用机制也进行了进一步分析。     

Mg-13Gd-1Zn合金的组织与力学性能

研究了铸态、退火态、挤压态和T5时效态Mg-13Gd-1Zn三元合金的显微组织和力学性能。结果表明,合金的铸态组织由α-Mg、(Mg,Zn)₃Gd和14H-LPSO长周期相组成。合金在均匀化退火和热挤压后的直接时效(T5)过程中都发生了晶内14H-LPSO相的沉淀析出,表明合金中14H-LPSO的沉淀相变发生在一个很宽的温度范围(200~510℃)。在挤压后合金的直接时效(T5)过程中发生了β'及β₁相的沉淀析出。在沉淀强化和LPSO强化的共同作用下,合金的屈服强度、抗拉强度和伸长率分别为197 MPa、397 MPa和2.56%。在200℃/80 MPa和200℃/120 MPa两种实验条件下,Mg-13Gd-1Zn合金的抗蠕变性能均优于WE54合金。     

微量钪对高Cu/Mg比Al-Cu-Li-Mg合金组织与性能的影响

利用金相显微镜、透射电子显微镜和拉伸试验等手段,研究了微量Sc对高Cu/Mg比Al-3.5Cu-1.5Li-0.5Mg-0.12Zr合金组织和拉伸性能的影响.结果表明:在Al-3.5Cu-1.5Li-0.5Mg-0.12Zr合金中加入0.10%Sc消除了合金铸态枝晶组织,有效抑制合金再结晶,明显提高了合金的强度和塑性,但晶粒细化效果不明显;添加0.15%和0.25%Sc显著细化合金铸态晶粒组织,塑性随Sc增加而提高,但添加0.25%Sc促进合金再结晶,合金强度显著降低.     

稀土Y对Mg-6Zn-1Mn合金显微组织和力学性能的影响

利用光学显微镜、X射线衍射仪、扫描电子显微镜、万能力学试验机等手段,系统研究了不同含量Y(1%~6%(质量分数))对Mg-6Zn-1Mn合金显微组织和力学性能的影响。结果表明,随着Y的不断增加,Mg-6Zn-1Mn系铸态合金主要物相演变规律为α-Mg+Mg7Zn3→α-Mg+I→α-Mg+W→α-Mg+X,这主要归因于不同的Zn/Y原子比。研究发现,当Y含量低于2%时,挤压可使晶界和晶粒内部析出细小弥散的第二相,同时提高了合金强度和室温延展性。而随着Y的进一步增加,第二相颗粒变大,且主要存在于晶界,热挤压过程中晶粒不易被挤碎,弱化了析出相与基体的界面能,最终使得挤压态合金综合力学性能降低。     

Bi对Mg-3Al-3Nd合金显微组织和力学性能的影响

使用扫描电子显微镜(SEM)和光学显微镜(OM)观察、X-射线衍射(XRD)分析以及力学性能测试等手段研究了Bi含量对Mg-3Al-3Nd合金的显微组织和力学性能的影响。结果表明：添加Bi元素可细化Mg-3Al-3Nd合金的组织。当Bi含量(质量分数)为1%时晶粒最小,晶粒尺寸从1854±58 μm减小到890±64 μm;Mg-3Al-3Nd合金由呈网状分布在晶界的Al₁₁Nd₃相和分布在晶内的颗粒状Al₂Nd组成;随着Bi含量的提高Al₁₁Nd₃相和Al₂Nd相的数量减少,晶内的BiNd相数量增加;Bi能明显改善Mg-3Al-3Nd合金室温和高温力学性能,Bi含量为1%时其室温和高温力学性能最佳。室温抗拉强度和延伸率分别为167±2.3 MPa和(16.1±0.3)%,高温抗拉强度及延伸率分别为136±1.7 MPa和(19.3±0.3)%。     

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.     

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.     

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.……     

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.