退火对大变形异步-同步复合轧制超细晶TWIP钢组织与性能的影响

研究了不同退火温度对大变形异步与同步复合冷轧制TWIP钢(Fe-0.5C-18.6Mn-1.5Al-0.5Si)的组织和性能的影响,结果表明:经96%大变形轧制后的材料组织明显细化,抗拉强度从593 MPa提升至2021 MPa;在500℃以下退火,大变形轧制超细晶TWIP钢未发生再结晶;在500~600℃发生部分再结晶;在600℃以上则发生完全再结晶。随着退火温度升高,材料强度降低,但塑性增加,大变形异步-同步轧制后经700℃退火获得了平均晶粒尺寸600 nm的超细晶TWIP钢,并表现出优秀的综合力学性能,其强度、塑性分别达到1114 MPa、59.4%。此外,制备的TWIP钢在500℃~600℃退火时,奥氏体基体中生成了大量细小弥散的硬质DO3结构的(Fe,Mn)3(Al,Si)型金属间化合物,显著提高了材料强度。     

低温薄规格取向硅钢初次再结晶组织对二次再结晶行为的影响

取向硅钢成品带材具有锋锐的Goss织构,其前提是需要保证在高温退火过程中能发生完善的二次再结晶,而合适的初次再结晶组织是发生二次再结晶的关键要点之一,探索初次再结晶组织对二次再结晶行为的影响具有重要的研究意义。分析了低温薄规格取向硅钢在不同脱碳退火时间条件下的初次再结晶组织,并研究了初次再结晶组织对二次再结晶行为的影响规律。结果表明:在脱碳退火温度880℃条件下,最佳退火时间约为3 min,此时高温退火可发生完全二次再结晶。延长脱碳退火时间,初次再结晶组织平均晶粒尺寸增大,导致二次再结晶不完善,高温退火后出现"细晶"组织。二次再结晶不稳定很大程度是初次再结晶组织中心层的{100}〈025〉取向晶粒长大所致,最终未发生二次再结晶的"细晶"组织也多为{100}〈025〉取向。     

钽丝的织构和再结晶行为研究

研究了变形钽丝在不同温度下退火后的织构演变和再结晶行为，发现1360℃退火后钽丝初次再结晶基本完成；1500℃退火后，钽丝中发生了二次再结晶，晶粒异常粗大。提出了拉拔钽丝的再结晶织构模型。     

热处理对AZ31B镁合金轧板组织和性能的影响

研究了AZ31B镁合金轧板经不同温度、时间退火后的组织和性能及其再结晶行为。结果表明,热轧板材在退火过程中主要发生再结晶;退火后,强度略有下降,但伸长率明显提高;在523K下退火,保温60min,可获得平均晶粒直径为10μm的细晶组织,其抗拉强度为258MPa,断裂伸长率为22.3%,综合性能较好。热轧态板材呈脆性准解理断裂,退火后转变为韧性断裂。     

135°ECAP+旋锻变形工业纯钛的热稳定性研究

对经过135°ECAP+旋锻变形后的工业纯钛100,150,200,250,300,350,400,450℃和500℃下保温1h退火。采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、拉伸试验机及显微硬度仪等技术研究ECAP+旋锻变形工业纯钛退火后的组织与性能变化。结果表明:在400℃以下退火时,显微组织中位错密度降低,晶界逐渐清晰,变形组织未发生明显变化,材料的抗拉强度和显微硬度略有降低,伸长率增加不明显;在400℃以上退火时,随着退火温度的升高,发生再结晶,晶粒尺寸明显增大,平均晶粒尺寸约为5μm,材料的抗拉强度和显微硬度均出现明显降低,伸长率增加。拉伸断口表明,ECAP+旋锻变形退火后工业纯钛的拉伸断裂均为韧性断裂。随着退火温度的升高,韧窝尺寸变大,韧窝深度变深。     

退火温度对GH3600合金箔材组织与性能的影响

目的 探究退火温度对GH3600镍基高温合金箔材微观组织及力学性能的影响。为制备综合性能良好的GH3600箔材提供参考。方法 将厚度为2 mm的铸态板材反复轧制退火得到组织均匀的0.3 mm厚度带材,再利用四辊冷轧机将带材轧制成厚度为0.1 mm和0.05 mm的箔材,然后将2种厚度箔材在950、1 000、1 050 ℃下保温1 h后空冷。通过金相观察、电子探针、EBSD检测及XRD分析来研究箔材的微观组织演变。通过拉伸实验检测箔材的室温拉伸性能。结果 随着变形程度的增大,轧制态箔材晶粒沿轧制方向被拉长得更加明显。在相同热处理参数下,0.05 mm退火态箔材晶粒尺寸更小。退火后,箔材晶粒发生了回复再结晶并析出了细小的碳化物。随着退火温度的升高,晶内碳化物逐渐减少,孪晶界比例增大,再结晶程度及晶粒尺寸增大。0.05 mm箔材在1 050 ℃退火时,其晶粒迅速粗化,在厚度方向上出现单层晶,导致箔材的抗拉强度及延伸率出现异常降低的现象,即“越小越弱”的尺寸效应。结论 适宜的热处理工艺有助于改善箔材的微观组织,进而提高其力学性能。0.05 mm箔材在950 ℃下退火1 h时,其延伸率为19.1%,屈服强度以及抗拉强度分别达到293 MPa和560 MPa,综合力学性能良好。     

ECAP变形对超细晶铜再结晶行为的影响

为研究ECAP变形对超细晶铜再结晶行为的影响,室温条件下对纯铜进行12道次等通道转角挤压(ECAP)变形,分别在100、150、280℃下对不同道次的超细晶铜进行退火处理,分析其硬度及微观组织变化规律.结果表明:经12道次ECAP变形后,铜的晶粒尺寸细化到约250 nm,硬度达146 HV;随着变形道次增加,超细晶铜的热稳定性降低,软化速度加快,在150℃退火时,1道次超细晶铜完成再结晶的时间约为20 h,12道次为0.5 h;12道次ECAP超细晶铜等温退火温度越高,完成再结晶时间越短,150℃完成再结晶时间约为1 200 s,200℃时缩短至600 s,280℃时再结晶仅需50 s;利用Arrhenius公式计算了再结晶激活能,1道次约为1 eV,12道次为0.78 eV,ECAP变形降低了铜的再结晶激活能.     

快速凝固/粉末冶金法制备ZK60高强镁合金

采用快速凝固/粉末冶金法(RS/PM)制备块体ZK60(Mg-5.52Zn-0.33Zr,质量分数/%)镁合金,研究了挤压态合金在200,300℃退火1h后微观组织和力学性能的变化.结果表明:挤压致密化过程中,合金粉末颗粒在剪切力作用下被拉长,内部晶粒碎化成小角度亚晶粒、位错胞和条带状亚晶,第二相纳米颗粒沿亚晶界随机分布;随后200℃退火后,组织发生不完全再结晶,位错密度有所降低;而在300℃退火后,合金组织发生完全再结晶,形成平均尺寸约2.5μm的等轴晶,同时晶内析出大量β2′相.挤压态合金的屈服强度和延伸率分别为394MPa,15.2%;随着退火温度的升高,强度略有下降,塑性提高,合金综合性能优异.     

退火温度对超细钼丝性能的影响

通过调整退火温度测试不同温度下超细钼丝的力学性能,探讨退火温度对超细钼丝力学性能影响的规律,从而制定钼丝最佳退火工艺.结果表明,在900～1 100℃退火,超细钼丝的延伸率变化不明显,而在1 100～1 350℃退火,延伸率发生了突变;结合断口分析得知,900～1 100℃退火主要发生回复,未消除加工形成的轴向织构,而1 350℃退火,超细钼丝发生了再结晶,完全消除了加工织构,所以综合性能得到改善.依此推荐超细钼丝最佳连续退火工艺参数为:在氢气保护下,移动速度为10 m/min,加热温度在1 350℃左右.     

微量Sc和Zr对Al-Mg合金组织和性能影响的研究

用硬度法，金相显微镜，扫描电镜（SEM）和力学性能检测等方法，研究了微量Sc和Zr对Al-5%Mg合金显微组织，再结晶温度和力学性能的影响。实验结果表明，添加0.17%Sc和0.08%Zr的合金铸态组织得到显著细化，枝晶组织在相当程度上得到消除；合金的再结晶起始温度约为300℃，比不加Sc和Zr的合金再结晶起始温度提高了约150℃，添加了Sc和Zr的合金没有确定的再结晶终了温度，其再结晶是一种连续，缓慢的过程，一直到575℃合金仍然保留着大量的变形组织；添加了钪和锆后的合金在稳定化退火后的强度提高，特别是高温退火后可以保留较高的强度。     

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.……     

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.……     

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...     

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.     

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.     

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.     

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 ...