铸造铝锂合金强韧化研究现状与展望

铸造铝锂合金具有低密度、高模量、高比强度和比刚度等优点,适用于制备复杂薄壁构件,是航空航天、国防军工行业理想的结构材料。基于铸造铝锂合金的组织特征,探索提升合金强塑性的有效途径,可以夯实铸造铝锂合金在轻量化领域的优势地位,扩大其应用范围。首先,概括了国内外铸造铝锂合金的发展历程,归纳了铸造铝锂合金的组织特征与强韧化机制。然后,围绕铸造铝锂合金强韧化研究的最新进展,系统分析了合金化与热处理对铸造铝锂合金微观组织及力学性能的影响规律,总结了提升铸造铝锂合金强塑性的主要途径。最后,面向铸造铝锂合金实际工程需求,对其强韧化处理中尚存的科学难题与未来的研究方向进行了探讨与展望。     

挤压铸造与超声处理对铸造铝锂合金组织与性能的影响

目的 研究挤压铸造与超声处理工艺对铸造铝锂合金组织与性能的影响规律,分析工艺改变对组织细化及性能提升的作用机理,解决传统重力铸造下铝锂合金性能较差的问题。方法 将挤压铸造（SC）与超声处理（UT）相结合制备Al-2Li-2Cu-0.5Mg-0.2Zr合金,在熔体超声2 min后,以50 MPa的挤压力制备合金,探究各工艺对铸造铝锂合金显微组织与力学性能的影响。结果 与传统的重力铸造（GC）相比,SC合金的孔隙率和成分偏析显著降低,晶粒尺寸也明显减小,特别是经过UT+SC处理的合金得到了进一步优化。经UT+SC处理后,Al-2Li-2Cu合金的极限抗拉强度（UTS）、屈服强度（YS）和伸长率分别为235 MPa、135 MPa和15%,与GC合金相比,分别提高了113.6%、28.6%、1 150%,与SC合金相比,分别提高了5.4%、3.8%、15.4%。结论 UT+SC工艺能明显提升铸造铝锂合金的性能。UT+SC制备的Al-Li合金的强度和伸长率的提高归因于孔隙率的降低、晶粒细化和第二相的均匀分布。将挤压铸造与超声处理相结合制备铸造铝锂合金解决了重力铸造下合金性能较差的问题,为满足航...     

液态动压实铝锂合金在时效过程中的结构转变

采用液态动压实(LDC)工艺制备的四种铝锂合金在时效过程中强化相的析出规律进行了研究。用 TEM 观察了析出相在晶内、亚晶界和位错上的析出分布。结果表明:四种合金的共同析出相为δ′(Al_3Li),β′(Al_3Zr)和δ′(Al_3Li)的复合析出相。改变合金中的铜、镁、锂含量,对强化相θ′(Al_2Cu),T_1(Al_2CuLi)和 S′(Al_2CuMg)的形成有较大的影响。同时也发现在190℃时效有利于β′+δ′复合相,S′和 T_1相的析出.     

金属型重力铸造高强度铝铜合金

目的 针对铝铜合金热裂敏感性高、难以进行金属型铸造的难题,研究其合金成分、铸造工艺、组织与性能的关系。方法 首先充分分析铸造铝铜合金的凝固机制与特点,在ZL205A合金基础上,设计了新型合金成分以及两种铸造试样模,经过熔炼、铸造与热处理,获得砂型铸造与金属型铸造试样,进行力学性能测试、组织分析,并观察试样的抗热裂性。结果 两种铸造试样都获得了较高的力学性能,铸态及T6态全部为等轴晶组织,成功避免了热裂问题,并提高了合金的力学性能;金属型铸造试制了油马达铸件。结论 证明了通过铝铜合金的成分优化设计,以及含钪复合细化剂的合理匹配,采用金属型铸造获得等轴晶组织,进而避免粗大枝晶组织,是克服热裂问题的关键,从而实现金属型铸造高强度铝铜合金。     

强电场对预拉伸变形1420合金效行为的影响

对１４２０铝锂合金进行预拉伸变形电场时效处理，并运用透射电镜，拉伸试验研究了强电场对１４２０合金的显微以及力学性能的影响，结果表明：强电场使δ’相数量增多，而且细小弥散化，可以显著提高合金的强度。     

2090+Ce铝锂合金时效组织形成及其强化机制

以2090铝锂合金作为参照,细致地观察了2090+Ce铝锂合金时效组织特征及其形成规律。首次利用图形分析等手段,对比研究了2090和2090+Ce铝锂合金中沉淀相尺寸分布规律,通过对两合金中δ′相和T_1相生长、粗化行为的研究,探讨了微量稀土Ce的作用机制。研究中发现添加微量稀土Ce,对时效初期δ′相的生长有一定的抑制作用,而对T_1相的析出却有一定的促进作用,其T_1相表现出较小的长厚比。在深入观察2090+Ce合金位错组态特征的基础上,计算了δ′相、T_1相的强化贡献及其综合效应。发现合金中位错组态随时效条件发生变化。T_1相与位错间的交互作用形式是切过和绕过的混合型,两相复合强化形式与时效时间有关。对比研究了2090和2090+Ce铝锂合金板材屈服强度各向异性及其形变织构、人工时效等因素的影响作用,探究了沉淀相强化作用与两合金板材屈服强度各向异性间的内在联系以及微观形变和断裂特征随取向角、时效条件的变化。结果表明T_1相等沉淀相对铝锂合金屈服强度各向异性以及断裂特征有着直接的影响,并提出了一修订的塑性内合物模型。     

铝锂合金研究开发的历史与现状

综述了国内外关于铝锂合金的研究概况；对铝锂合金的实际应用进行了简要归纳；分析和评述了铝锂合金今后的发展态势。     

Li对7075铝合金钻杆材料微观组织与摩擦磨损行为的影响

采用热压烧结制备7075-(0%,0.5%,1%,2%,质量分数，下同)Li合金，研究Li对7075铝合金微观组织及摩擦磨损性能的影响。结果表明：7075-0.5Li合金在60 kN烧结压力下致密度可达到99%以上。铝合金由α-Al相、η相和S′相组成；随着Li含量增加至2%,η相减少，δ′相、δ相增多，但α-Al仍为主相。铝合金的硬度和磨损率分别为71.25HV和3.50×10^-3 mm³·N^-1·m^-1,随Li含量增加，铝锂合金硬度降低，磨损率升高，但7075-0.5Li比铝合金的硬度更高，磨损率更低。7075-Li合金均发生了氧化磨损，同时还发生了黏着磨损。铝锂合金随Li含量增加，η相减少，硬度降低，Al₂O₃脆性大从而与基体结合较弱，微观组织枝晶间距增大，导致合金由磨粒磨损逐渐转变为黏着磨损，耐磨性能逐渐降低。与铝合金相比，热压烧结制备的7075-0.5Li合金显示了更好的耐磨性能。     

快速凝固粉末铝锂合金的研究及发展(一)

本文综述了快速凝固粉末铝锂合金在成分选定、粉末的制取和成型、合金组织与性能等几方面的主要研究成果。分析了粉末冶金铝锂合金的发展前景和趋势。简要介绍了铝锂合金粉末冶金的两种新技术的基本原理。     

铝锂合金TIG焊缝中细晶层成因的研究EI

铝锂合金ＴＩＧ焊缝边缘存在独特的细晶层组织，而焊缝金属的联生结晶被抑制。细晶层的形成与铝锂合金中锂、锆和钛等合金元素的性质以及这些元素对熔池结晶过程的影响有关。     

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.