GH4720Li合金粗晶组织热变形细化预测研究

目的 研究不同变形参数下GH4720Li合金动态再结晶行为,建立GH4720Li合金粗晶组织动态再结晶细化的预测模型,为铸态初轧GH4720Li合金锻造工艺参数制定、粗晶组织消除、细晶组织获得提供理论支撑。方法 在温度为1 030～1 150℃、应变速率为0.01～10 s^-1条件下,对铸态初轧GH4720Li合金粗晶组织进行了热压缩实验,分析了不同变形参数下合金的动态再结晶行为。研究了合金动态再结晶演化机制,构建了GH4720Li合金粗晶组织动态再结晶预测模型和晶粒尺寸模型,并结合实验对模型的准确性进行了验证。结果 在合金热压缩过程中,流变应力表现出明显的加工硬化、动态回复和动态再结晶软化平衡特征,粗晶组织动态再结晶细化程度可以通过流变应力变化间接反映。根据应力–应变数据计算得到合金的热变形激活能为1 230.48 kJ/mol,确定了Z参数与峰值应变和临界应变之间的关系,发现峰值应变和临界应变与Z参数均呈线性关系。通过观察合金微观组织发现,在变形过程中发生了非连续动态再结晶和连续动态再结晶,2种变形机制共同影响着粗晶组织的演化,所建立的动态再结晶细化模型和动态...     

锻态GH4169合金热变形本构方程及热加工图

目的 研究锻态GH4169合金的热变形行为,获得优化的热加工参数。方法 采用Gleeble 3500热模拟实验机对锻态GH4169合金进行不同工艺参数的热压缩实验,建立锻态GH4169合金的热变形本构方程,分析流变应力与热加工参数之间的关系。根据获得的流变应力–应变曲线建立锻态GH4169合金的热加工图。采用金相显微镜观察锻态GH4169合金变形后的显微组织。结果 锻态GH4169合金的应力随变形温度的增加和应变速率的降低而降低。基于锻态GH4169合金的热加工图可知,锻态GH4169合金可热加工的区域分别为987～1 027℃/0.026～0.01 s^-1和1 070～1 100℃/0.026～0.01 s^-1,最优热加工参数分别为1 000℃/0.01 s^-1和1100℃/0.01s^-1。通过金相组织结果分析可知,锻态GH4169合金无论在低温高应变速率条件下,还是在高温低应变速率条件下都发生了再结晶。对于热加工图中的流变失稳区,合金的动态再结晶主要与变形热有关。对于热加工图中可热加工的区域,合...     

GH4706合金的热变形行为与显微组织演化

在Gleeble 3800热模拟试验机上进行GH4706合金的热压缩实验,研究了变形温度为900～1150℃、应变速率为0.001～1s-1范围内合金的热变形行为.结果表明:GH4706合金的真应力真应变曲线呈现出流变软化特征,随变形温度增加或应变速率减小,峰值应力逐渐降低,峰值应变逐渐减小.合金的本构关系可由双曲正弦函数描述,变形激活能为435.36kJ/mol,应力指数为4.13.合金的显微组织演化机制与Z参数密切相关,高Z值条件下主要发生动态回复,低Z值条件下主要发生动态再结晶与再结晶晶粒粗化.GH4706合金发生完全动态再结晶且不发生晶粒粗化的临界lnZ值为35.     

温度和应变速率半固态Alsi7Mg合金变形性的影响

采用Gleeble-1500热模拟试验机研究了温度和应变速率对半固态AlSi7Mg合金变形性的影响.从中得知,半固态合金的压缩流动应力不仅是变形温度的函数,而且是应变速率的函数,变形温度和应变速率决定了半固态压缩变形的特征.     

新型高强Al-Zn-Mg-Cu合金的热变形行为和热加工图

采用热力模拟实验方法进行热压缩变形实验,研究了一种新型Al-Zn-Mg-Cu高强铝合金铸态组织在变形温度为300～450℃,应变速率为10-3～10s-1,压缩变形量为50%条件下的热变形行为,建立了该合金的热加工图。变形温度和应变速率对该合金流变应力的影响显著;实验参数条件下,该合金流变应力曲线呈现稳态动态回复型曲线特征。热加工图和组织分析表明:当应变较小时(ε=0.1),合金具备铸态组织特征,合适的热加工参数:350～450℃,应变速率10-3～10-2s-1;当应变较大时(ε=0.5),合金具备锻态组织特征,较佳的热加工参数:300～450℃,应变速率10-3～10-1s-1。     

冷拔态GH4738合金热变形本构方程及热加工图

目的 研究紧固件用冷拔态GH4738合金棒材在不同工艺参数下的热变形行为,为紧固件热加工工艺参数优化提供理论指导。方法 采用Gleeble-3500热模拟实验机对冷拔态GH4738合金棒材在变形温度1 000~1 080 ℃、应变速率1~10 s⁻¹条件下进行了热压缩实验,变形量为50%。计算了该合金的材料常数和变形激活能Q,建立了基于峰值应力的冷拔态GH4738合金的本构方程,根据动态材料模型理论绘制了冷拔态GH4738合金的能量耗散图和失稳图,获得了合金在不同应变下的热加工图,并讨论了显微组织演变情况。结果 冷拔态GH4738合金的流变应力随着变形温度的增加或应变速率的减小而降低。线性回归的相关系数证实了描述该材料热变形行为的本构方程的准确性。基于冷拔态GH4738合金的热加工图及显微组织验证结果可得,冷拔态GH4738合金的主要失稳区工艺参数区间为1 000~1 035℃/0.12~3 s⁻¹,1 030~1 072℃/ 0.25~10 s⁻¹和1 075~1 080 ℃/2.72~10 s⁻¹。热加工较佳工艺条件为1 000~1 028 ℃/0.02~0.14 s⁻¹和1 040~1 080 ℃/ 0.06~0.74 s⁻¹。结论 通过对冷拔态GH4738合金热变形本构方程和热加工图进行研究,获得了冷拔态GH4738合金优化的热变形工艺参数,可用于指导冷拔态GH4738合金的紧固件热加工成形。     

GH4049合金的热变形行为及组织演变

在Gleeble-1500热模拟机上进行GH4049合金的热压缩实验,获得合金在温度为1090~1180℃、应变速率为0.1~50s-1条件下的应力-应变曲线。对峰值应力进行线性回归获得合金在不同变形条件下的材料常数,通过非线性回归建立合金的热变形本构方程。结果表明:随着变形温度升高,动态再结晶更加充分,晶粒尺寸变大;随着应变速率增加,晶粒组织趋于均匀,晶粒尺寸先减小后增大。     

铸态Mg−2Sc−2Y−0.5Zr合金热压缩行为及热加工图

目的 研究铸态合金Mg?2Sc?2Y?0.5Zr合金热压缩行为及热加工图,根据合金的用途和再结晶程度,确定最佳热加工艺参数,为合金后续变形提供参考。方法 通过实验设计合金成分,称取一定质量的纯镁锭和二元中间合金,在真空熔炼炉中加热至760 ℃,保温至熔化,搅拌,静止,然后在钢磨具中空冷,得到合金锭。实际成分通过电感耦合等离子体原子发射光谱法测定;切取合适大小的铸锭进行X射线衍射实验。用于热压缩的铸态样品为圆柱形试样(?10 mm×15 mm) ,在进行热压缩实验前,对所有样品表面进行抛光。使用Gleeble?3800热压缩模拟试验机对铸态Mg?2Sc?2Y?0.5Zr合金进行热压缩试验,变形温度为573~723 K,应变速率为0.001~1 s^?1。经热压缩后将各试样立即进行水淬,以保持压缩变形组织。将压缩样品沿着纵轴切割压缩样品,然后抛光、蚀刻,并使用扫描显微镜进行检查,以观察微观结构的演变,计算该合金的变形激活能,并构建合金高温变形的本构方程,建立真应变为0.5时的热加工图。结果 得到了铸态Mg?2Sc?2Y?0.5Zr合金热变形本构方程及真应变为0.5时的热加工图,合金热变形发生了动态回复和动态再结晶,合金的热变形激活能Q为198.58 kJ/mol。结论 根据用途和再结晶程度,铸态Mg?2Sc?2Y?0.5Zr合金的最佳加工参数为变形温度623~673 K、应变速率0.001~0.01 s^?1,以及变形温度723 K、应变速率0.001~1 s^?1。     

基于流动应力曲线的AZ80镁合金动态再结晶动力学表征

热物理模拟获得了铸态AZ80镁合金热压缩真应力-应变曲线,以此作为计算动态再结晶体积分数演变的底层数据.通过求解流动应力的双曲正弦表征模型,获得了本构模型与动态再结晶激活能等重要参数.分析峰值应力出现之前与之后的硬化曲线,识别了真应力-应变曲线所隐含的关键应变点:临界应变,峰值应变及最大软化速率应变.进一步引入表征晶体...     

GWN751K镁合金热压缩实验研究

在Gleeble-1500D热模拟机上进行了单向热压缩试验,研究了GWN751K镁合金在变形温度为623-773K,应变速率为0.002-2s-1条件下热变形行为,变形量为60%.结果表明,在相同变形温度条件下,流变应力随变形速率的增加而上升,在相同的应变速率条件下,流变应力随着变形温度的升高而下降,计算出其平均激活能Q为228.61kJ/mol,应力指数n为4.2.根据材料动态模型,计算并分析了GWN751K合金的热加工图,并确定了合适的挤压加工条件为723K,0.01/s.通过对合金的挤压试验研究,验证了加工条件,挤压后的合金断裂强度为320MPa,延伸率为18%,较铸态合金有显著提高.     

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.……     

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.     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from