LD7铝合金热变形研究

在Gleeble-1500热模拟机上对LD7铝合金进行等温热变形实验,变形温度为300～500℃,应变速率为0.01～10s-1,研究其热变形的流变应力行为、显微组织及软化机制.结果表明LD7铝合金真应力-真应变曲线表现出动态回复特征,在应变速率ε=1.0s-1,变形温度高于420℃时,应力出现锯齿波动,表现出不连续动态再结晶特征.合金在压缩过程中主要软化机制为动态回复,同时也存在动态再结晶.变形后晶粒尺寸随变形温度升高而增大,随变形速率增加而减小.     

含钪Al-Zn-Mg合金的热变形行为和显微组织EI北大核心CSCD

采用Gleeble-1500热模拟试验机对含钪Al-Zn-Mg合金进行热压缩实验,研究了合金在不同热压缩条件下的热变形行为和显微组织。结果表明:合金的流变应力随应变速率的增大而增大,随变形温度的升高而减小。该合金热压缩变形的流变应力行为可用Zener-Hollomon参数来描述,其热变形激活能为150.25kJ/mol。在变形温度为380℃,应变速率为1s-1条件下,合金组织中存在大量的位错墙,表明发生了动态回复现象。随着变形温度的升高,当温度为500℃时,合金中出现了再结晶晶粒,说明主要软化机制逐步由动态回复转变为动态再结晶。     

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。     

轧制态7A60铝合金的热压缩显微组织及流变行为

对轧制态7A60铝合金在应变速率为0.1~0.01s-1、变形温度为250~350℃条件下热压缩的显微组织特征和流变应力进行实验研究。结果表明:随着应变速率的降低和温度的升高,材料的各向异性减弱,均匀性增强,晶粒发生明显粗化;在热变形的过程中该合金的主要软化机制为动态回复和动态再结晶,峰值应力随应变速率的增加而增大,随温度的升高而降低,在应变速率为0.01s-1时发生了明显的非连续动态再结晶行为。合金热变形的流变应力行为可用双曲正弦函数来表示,其热激活能为438.981kJ/mol。     

Cu-2.32Ni-0.57Si-0.05P合金热压缩变形研究

在Gleeble-1500D热模拟试验机上,对Cu-2.32Ni-0.57Si-0.05P合金在应变速率为0.01～5s-1、变形温度为600～800℃、最大变形程度为60%条件下,进行恒温压缩模拟实验研究.分析了实验合金在高温变形时的流变应力、应变速率及变形温度之间的关系,研究了变形温度对合金显微组织的影响.计算了合金高温热压缩变形时的应力指数n、应力参数α、结构因子A以及平均热变形激活能Q.结果表明:合金的流变应力随变形温度升高而降低,随应变速率提高而增大.热变形过程的流变应力可用双曲正弦本构关系来描述.当变形温度高于750℃时,合金流变曲线呈现出明显的动态再结晶特征,合金显微组织为完全的动态再结晶组织.合金的热加工宜在应变速率为0.1～1s-1、温度为700～800℃范围内进行.     

Mg-9Gd-3Y-0.3Zr合金高温塑性变形行为研究

以Mg-9Gd-3Y-0.3Zr合金为研究对象,采用热模拟等温压缩的试验方法,利用Arrhenius关系式,分析了合金应力与应变的关系,同时利用金相显微镜和扫描电镜,观察合金在热变形过程中组织的演变。结果表明,合金高温等温压缩变形的真应力-真应变曲线属于动态再结晶型,并且当应变速率ε一定时,温度升高,峰值流变应力下降,当温度一定时,应变速率ε增大,峰值流变应力和它所对应的应变值均提高;变形过程中随着温度的升高,合金发生不同程度的再结晶。当变形温度为623K时,组织变化以动态回复为主,变形温度提高到673K,开始出现再结晶现象,温度达到773K时得到完全再结晶组织。     

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.     

β21S钛合金高温变形行为研究

在Gleeble-1500热模拟试验机上对β21S钛合金进行了高温恒应变速率压缩实验,研究其在变形温度为750～1100℃,应变速率为0.01～1s-1条件下的流变应力及微观组织变化规律,计算了变形激活能及应力指数,并给出了流变应力的计算模型.结果表明:合金的流变应力随应变速率的增大而增大,在恒应变速率下,其应力水平随温度的升高而降低;在较低温度和高应变速率变形时,合金仅发生回复现象,随着温度的升高和应变速率的降低,有部分再结晶发生且再结晶程度逐渐增大;计算得出实验条件下的变形激活能和应力指数分别为211.04kJ/mol和4.0129.     

β21S钛合金高温变形行为研究EI北大核心

在Gleeble-1500热模拟试验机上对β21S钛合金进行了高温恒应变速率压缩实验,研究其在变形温度为750～1100℃,应变速率为0．01～1s^-1条件下的流变应力及微观组织变化规律,计算了变形激活能及应力指数,并给出了流变应力的计算模型。结果表明：合金的流变应力随应变速率的增大而增大,在恒应变速率下,其应力水平随温度的升高而降低;在较低温度和高应变速率变形时,合金仅发生回复现象,随着温度的升高和应变速率的降低,有部分再结晶发生且再结晶程度逐渐增大;计算得出实验条件下的变形激活能和应力指数分别为211．04kJ／mol和4．0129。     

含Sc超高强Al-Zn-Cu-Mg-Zr合金的热变形行为和微观组织

采用热模拟实验对含Sc超高强Al-Zn-Cu-Mg-Zr合金在应变速率为0.001～10s-1、变形温度为380～470℃的条件下进行了热压缩实验.研究了实验合金的流变应力行为和微观组织演变.结果表明:流变应力随变形温度升高而下降;随应变速率增加峰值应力也相应增加.随变形温度升高和应变速率降低,合金动态再结晶的程度加深,亚晶尺寸变大.含Sc超高强Al-Zn-Cu-Mg-Zr合金,形成了Al3Sc弥散相,该相可强烈抑制再结晶.合金主要软化机制为动态回复伴随动态再结晶.     

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 ...     

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     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.