高熔点差三元合金累积叠轧-扩散合金化制备工艺

为解决高熔点差多元合金制备方法存在的元素偏析、合金性能受限、制备成本高等问题,提出了高熔点差组元合金的累积叠轧-扩散合金化制备新工艺。采用SEM、EDS、TEM、XRD和万能试验机表征了累积叠轧-扩散合金化Cu-21Ni-5Sn合金的组织和性能,研究了累积叠轧和阶梯式扩散热处理工艺对Cu-21Ni-5Sn合金成分均匀性的影响和机理,并揭示了后续时效制度对Cu-21Ni-5Sn合金性能的影响和机理。结果表明：通过累积叠轧7道次+650 ℃/5 h+1000 ℃/8 h阶梯真空扩散热处理工艺,制备出了元素误差小于5%、成分均匀的Cu-21Ni-5Sn合金。采用累积叠轧实现减薄中间层、缩短扩散距离,增加晶界、位错等原子扩散通道,低熔点Sn元素与Cu、Ni元素在650 ℃形成高熔点(Cu,Ni)₃Sn金属间化合物临界层,在1000 ℃高温加速Cu、Ni元素扩散。Cu-21Ni-5Sn合金在40%预冷变形下于470 ℃时效60 min充分调幅分解,基体中析出致密的与基体共格的DO22及L12有序固溶体,与α铜基体之间的取向关系为(-1-1-1 )Cu//(-2-20)DO22,(-200)Cu//(-310)L12。合金抗拉强度达到峰值916 MPa,弹性模量为135.4 GPa,合金导电率达到6.23% IACS。     

金属熔体外场处理技术的研究进展

金属熔体外场处理技术是金属熔体处理技术的重要类别之一,它应用于金属半固态或低温液态流变成形等各种铸造场合,目的是实现凝固组织的整体均匀化和细化。基于性价比,提出了评价外场处理技术的3个原则:工艺简单原则、均匀细化原则和减少缺陷原则。结合对现有外场处理技术的客观评价,引荐了一种类似豆浆机原理的\"金属熔体切割破散处理技术\"。     

均匀化对TiN细化Al-Zn-Mg-Cu合金组织和硬度的影响

研究了均匀化处理对纳米TiN/Ti细化Al-Zn-Mg-Cu合金组织及性能的影响。结果表明,纳米TiN/Ti细化剂可显著细化铸态Al-Zn-Mg-Cu铝合金晶粒,使合金的铸态硬度（HV）从123提高至142.3。470℃×24h一级均匀化处理后,Al-Zn-Mg-Cu合金晶界第二相得到了比较充分的溶解,只有少量MgZn2相残留;经过（400℃×10h+470℃×24h）二级均匀化处理后,第二相溶解充分,但在均匀化处理之后的冷却过程中析出MgZn相,并均匀分布在晶粒中。     

高速匀浆法提取辣蓼茎中总黄酮

以辣蓼茎为原料,对匀浆法提取辣蓼茎中总黄酮工艺进行了研究,确定了最优工艺参数:提取1次,提取时间2 min,60%的乙醇溶剂,转速为20 000 r/min,料液比为1∶25 g/m L。在最佳条件下,提取并测定了辣蓼茎中总黄酮含量,结果表明,黄酮提取率为4.75%。     

Microstructural design of connective base cells for functionally graded materials

Control of compositions and microstructures plays a significant role on developing functionally graded material (FGM). The existing fabrication technologies allow placing multiple compositions in such a way that a desirable gradient of effective physical properties can be achieved. It is interesting to explore how to design microstructure for the same purpose. This paper introduces an inverse homogenization procedure to FGM design. A quasi-periodic base cell (PBC) is optimized for attaining a specific gradient of Young's modulus. To ensure proper connectivity between adjacent PBCs, heat sinks originally used in thermal conduction problem are employed as connection constraints. The capability of this technique is demonstrated by the examples of FGM microstructural design.     

Stability Problems in Soil‐Structure Interfaces: Experimental Observations and Numerical Study

This article presents experimental results of tests on soil‐structure interfaces carried out on a new “ring simple shear” apparatus specially developed at Ecole Nationale des Ponts and Chaussées, Paris, for such studies. In this apparatus strain localization takes place at or near the surface of the rotating steel drum that forms the soil‐structure interface. Depending on the conditions of tests, in terms of surface roughness, special instrumentation is capable of recording local as well as global response. Three tests on Hostun gravel at different confining radial pressures have been conducted and a deviatoric hardening model with nonassociated flow rule has been adopted for their numerical simulations. The point of inception of strain localization based on various theoretical considerations has been discussed and experimentally verified. The post‐peak behavior is simulated by employing a homogenization technique in which the soil sample is treated as a composite material consisting of a shear band surrounded by intact material. A deviatoric strain softening model has been adopted for the shear band. It is shown that the mechanism of failure and the response of the soil sample is reasonably well simulated. Although there are some concerns regarding the homogeneity of the sample, the post‐peak stage and the overall mechanical response of gravel‐steel interface are rather well reproduced.     

Tailoring materials with prescribed elastic properties

This paper describes a method to design the periodic microstructure of a material to obtain prescribed constitutive properties. The microstructure is modelled as a truss or thin frame structure in 2 and 3 dimensions. The problem of finding the simplest possible microstructure with the prescribed elastic properties can be called an inverse homogenization problem, and is formulated as an optimization problem of finding a microstructure with the lowest possible weight which fulfils the specified behavioral requirements. A full ground structure known from topology optimization of trusses is used as starting guess for the optimization algorithm. This implies that the optimal microstructure of a base cell is found from a truss or frame structure with 120 possible members in the 2-dimensional case and 2016 possible members in the 3-dimensional case. The material parameters are found by a numerical homogenization method, using Finite-Elements to model the representative base cell, and the optimization problem is solved by an optimality criteria method.

Numerical examples in two and three dimensions show that it is possible to design materials with many different properties using base cells modelled as truss or frame works. Hereunder is shown that it is possible to tailor extreme materials, such as isotropic materials with Poisson's ratio close to − 1, 0 and 0.5, by the proposed method. Some of the proposed materials have been tested as macro models which demonstrate the expected behaviour.     

Buckling of thin-walled orthotropic cylindrical shells under uniform external pressure.: Application to corrugated tin cans

The general instability of thin-walled orthotropic circular cylindrical shells under external pressure is investigated. The buckling pressure can be predicted with the use of simple analytical formulae derived from an asymptotic analysis of the corresponding eigenvalue problems. The results predicted by these formulae are compared with finite element solutions and the four types of experimental models investigated by Ross (Thin Walled Structures 1996;26(3):179–93). The comparison proved to be accurate enough for practical purpose except for experimental model 1.     

均匀化理论在多孔板结构优化中的应用研究

多尺度均匀化理论自从上世纪 70年代产生以来 ,就被认为是确定复合材料当量性能的一种不可替代的方法。本文将多尺度均匀化方法应用于基于有限元分析的多孔板结构优化设计中 ,简述了求解当量板有效弹性常数的均匀化理论 ,在此基础上 ,建立了基于有限元分析的多孔板结构优化流程 ,编写了FORTRAN程序 ,并将其与AN SYS软件相连接 ,完成了一个多孔板结构的优化设计 ,所得结果表明 ,它能够满足工程应用的需要 ,并为多孔板结构设计提供了一种新思路     

包裹体在确定成藏年代中的应用及应注意的问题

介绍了包裹体方法确定成藏年代的原理和方法。在包裹体测温和单井热史、生烃史恢复的基础上,运用包裹体方法分析了天东19井、磨13井和平昌1井的油气充注期次和充注时间。天东19井和磨13井发生了三期油气充注,其中天东19井三次油气充注时间分别为早三叠世、中侏罗世早期和中侏罗世晚期;磨13井三次油气充注时间分别为早中侏罗世、中晚侏罗世和晚白垩世―早第三纪早期。平昌1井发生两次油气充注,充注时间分别为中晚侏罗世和晚侏罗世―早第三纪。最后指出了运用包裹体确定成藏年代值得注意的一些问题。