ZA27合金部分重熔过程中组织的扫描电镜观察

用扫描电镜背散射电子成像技术，对经Zr变质处理的ZA27合金在半固态温度460℃部分重熔过程中的微观组织进行了观察，并对有关组织的成分进行了测定。结果表明，随着保温时间的延长，晶界处的共晶组织向初生晶内部扩散，趋于消失，晶粒由铸态时的等轴晶变为粒状晶。当保温10min时，未来得及溶入的共晶组织开始熔化，使组织分离为近粒状。到20min时，初生晶粒演变为粒径为40μm左右的球状颗粒，同时，晶粒中细小、弥散分布的η相由外到里逐渐长大，并伴有熔化现象。     

Al-Si合金在凝固过程中颗粒和枝晶组织的演变

通过改变和控制浇注温度、冷却速度和半固态保温时间，研究了亚共晶Al-Si合金在不同凝固条件下初生相形貌的演变。结果表明．浇注温度对初生相形貌的影响最大。当浇注温度在液相线附近，冷却速度为0．3℃／s，并在半固态状态下保温1～5min的条件下，初生相为理想的颗粒状组织。随着浇注温度和冷却速度的提高，初生相由颗粒状向枝晶组织演变。此外，添加晶粒细化剂有利于颗粒组织的形成。在试验的基础上，采用改进的Cellular Automaton(MCA)模型进行计算机数值模拟，研究了Al-Si合金在凝固过程中初生相的演变机制。     

横向静磁场对Cu-10%Ag合金定向凝固组织的影响

在有无横向静磁场条件下进行了Cu-10%Ag(质量分数)合金定向凝固实验,研究了横向磁场对Cu-10%Ag合金的宏观组织和微观组织及硬度的影响。发现无磁场条件下,合金晶粒较长,尺寸粗大,初生Cu枝晶臂直径和间距较粗大,取向较好,共晶组织粗大;1T横向磁场条件下,晶粒细化、增多,枝晶臂直径和间距较小,取向消失,共晶组织细化,硬度提高。通过对比有无横向磁场条件下初生Cu枝晶以及共晶组织变化,讨论了横向磁场对初生Cu枝晶及共晶组织的影响机理。     

半固态ZCuSn10铜合金二次加热组织的演化

采用热轧与重熔的SIMA法制备了ZCu Sn10铜合金半固态坯料。先通过多向热轧对ZCu Sn10铜合金坯料进行预变形,然后对其进行半固态温度区间保温不同时间的二次加热处理。使用光学显微镜、扫描电镜、能谱及图像分析软件等手段研究了坯料二次加热过程中微观组织的演化,并分析了α(Cu)球化组织的形成机制。结果表明:在热轧变形量为16%、加热温度为930℃时,随着保温时间的延长半固态ZCu Sn10铜合金坯料初生α(Cu)逐渐发生球化,平均晶粒直径先减小后增大,由二次加热保温8 min的68.24μm先减小至10 min的62.31μm然后增大至25 min的71.09μm;保温10 min时平均晶粒直径最小,液相率由保温8 min时的18.14%逐渐增加到保温25 min时的25.32%;形状因子随着保温时间的延长先减小后增加,由保温8 min时的2.91先减小至15 min时的1.67,然后增大到保温25 min时的2.43。保温15 min时的半固态组织最优,其平均晶粒直径为65.64μm、液相率为23.66%、形状因子为1.67。在半固态铜合金二次加热过程中,组织演变的主要机制是加热前期的晶粒合并长大和液相增加后的原子扩散导致的晶粒长大并球化。     

Zr变质SiCP/ZA27复合材料在部分重熔过程中的组织演变

用扫描电镜(SEM)背散射成像技术对Zr变质SiC_P/ZA27复合材料在部分重熔过程中的组织演变进行了研究,并与未变质复合材料及基体合金作了对比。结果表明:经0.2 wt% Zr变质的SiC_P/ZA27复合材料在460℃加热过程中(0min~30min),其基体组织依次经历了晶臂的快速合并,晶粒的长大,晶界区域的熔化、组织分离,最后经球状化形成触变成形所需的粒径较为均匀、细小、圆整的半固态浆料,在随后的保温过程中(30 min~80 min)未发现明显的粗化现象;未变质复合材料则形成相互连接的不规则组织,即使经长时间的保温(80 min),也未全部球状化;基体合金组织的分离快于变质复合材料,但在保温中的晶粒粗化却较为严重。加热初期晶粒的快速粗化是由共晶组织向晶内的迅速扩散引起的。本文作者从相变角度分析了组织的演变过程。     

铝合金非枝晶组织感应加热演变动力学研究

应用图象分析法系统研究了非枝晶A356铝合金感应加热时的组织演变规律,结合非线性拟合和晶粒长大动力学等研究,结果表明:A356铝合金初生α-Al晶粒在不同感应加热温度下的长大规律均符合奥斯瓦尔德熟化关系式Rn-Rn0=kt,在540℃～600℃的保温温度范围内,n值在2～3之间,k值在O.7～155之间.在固液两相区加热保温,α-Al晶粒长大速度要明显高于固相区加热保温时的长大速度,这与液相扩散系数要远大于固相的扩散系数相关.α-Al晶粒长大方式为,在固相区加热保温,共晶组织中β-Si颗粒通过扩散不断凝聚、粗化,致使晶界逐步消失,从而使α相合并长大,而在固液两相区加热保温,晶粒长大方式更为复杂,但圆整度均没有提高.     

快速凝固条件下Ni–Pb偏晶合金的组织演变机理研究

目的 研究过冷Ni–0.5%Pb(原子数分数)合金过冷组织的演化行为,阐明其组织演化和晶粒细化的基本机制。方法 采用熔融玻璃净化和循环过热方法制备出过冷度为0~255 K的试样,并结合枝晶生长的动力学–热力学模型,研究其深过冷快速凝固行为机制。结果 在0~255 K过冷度范围内,随着过冷度的增大,Ni–Pb偏晶合金的微观组织发生了2类晶粒细化现象,组织形态由粗大树枝晶向粒状等轴晶转变。结论 第1类粒状晶的形成是由于枝晶熟化和再辉重熔导致发达枝晶破碎,第2类粒状晶的形成是由于在应力和应变能的作用下,枝晶碎变和再结晶引起了晶粒细化。     

Mg对共晶Al-2％Fe合金显微组织的影响

为了消除粗大针状富铁相对Al-Fe合金组织和性能的不良影响，在金属型铸造共晶Al-2％Fe合金中添加了质量分数为0．2％～0．8％的合金元素Mg，利用光学显微镜和电子探针研究了Mg对共晶合金组织以及富铁相形态的影响．研究结果表明：共晶Al-2％Fe合金组织为针状Al3Fe相与（α-Al）相所组成的非规则共晶组织；添加Mg后，合金组织转变为由树枝状初生（α-Al）和枝晶间网状分布共晶体所组成的亚共晶组织，富铁相尺寸显著降低；随着Mg添加量的增加，初生（α-Al）枝晶二次枝晶间距增大，一次枝晶出现熔断。     

微波烧结Fe-2Cu-0.6C合金的保温时间对组织与性能的影响

对微波烧结Fe-2Cu-0.6C粉末冶金材料进行了1150℃不同保温时间下的性能和显微组织研究,并与常规烧结试样进行了对比.结果表明:微波烧结保温时间由5min增加至15min,试样的各项性能达到最佳:密度为7.22g/cm3,硬度HRB为78,抗拉强度为416.8MPa,延伸率为5.5%;保温时间延长至20min对试样性能影响不大.微波烧结的性能较常规烧结高.通过金相显微分析表明:微波烧结有着良好的微观结构,即小的、近圆形且均匀分布的孔隙结构,从而也有利于获得细小的晶粒和高的致密度;微波烧结较常规烧结有着更多片状和粒状珠光体,能显著改善其性能.由断口分析可知,常规烧结样品属于脆性穿晶断裂,而微波烧结样品为脆性穿晶断裂和韧窝型的穿晶韧性断裂的混合型断裂.     

液相线模锻法制备ZK60-RE镁合金半固态组织演变

给出了液相线模锻法制备ZK60-RE镁合金半固态坯料的实验方法和工艺参数,并研究了该方法制备的ZK60-RE镁合金在半固态等温热处理过程中的微观组织演变.结果表明:利用液相线模锻法可以制备半固态ZK60-RE镁合金坯料,半固态ZK60-RE镁合金坯料在保温时间较短的半固态等温热处理过程中能形成晶粒细小、晶粒粗化速度较为缓慢的球晶组织,晶粒在600℃保温15 min、610℃保温3 min和618℃保温0 min时分别达到最小,最小尺寸分别为35、45、30 μm,能够达到半固态加工实际化生产的较高要求.晶粒在不同的温度下随着保温时间的延长,晶粒的圆整度均逐渐变小,球晶化越来越好.     

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.     

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.……     

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...     

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.     

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.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

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.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...