材料织构与晶界特征分布及其性能增强

为探索织构变化规律及再结晶织构形成机制 ,采用激光超快速再结晶退火对Cu样品进行了处理 ,研究了织构转变的规律和织构控制手段 ,提出了再结晶织构形成的亚晶择优形核—微区选择生长—优势生长理论和数学解析模型并进行了计算机模拟。选取了LY12试验材料 ,经轧制 ,在不同退火条件下进行再结晶处理 ,得到不同形态的组织与织构 ,测定了GBCD ,研究其对高温力学性能和耐晶间腐蚀性能的影响。本文对上述实验研究结果作一综合概述和总结。

金属材料织构的激光超声检测研究

为了提高金属材料织构检测的准确性,设计一个金属材料织构的激光超声检测方法。首先对激光超声信号检测的信号进行了处理,然后采用有限元分析方法进行检测数值模拟,最后采用对金属材料织构进行了检测。实验结果表明,所研究的检测方法有效提高了检测准确性,可实际应用意义强。

立方晶系织构材料残余应力测定的H晶面衍射法

本文在Dolle理论基础上,对应力测定中织构材料的2θOscillation现象作了进一步分析,并设计实验予以考察和检验。理论与实验均表明,影响织构材料2θ与sin^2Ψ关系的本质原因是材料的弹性各向异性,其影响程度在X射线衍射分析中更直接地表现在晶体取向性的强弱上。一般讲,取向性愈明显,Oscillation就愈严重。对立方系材料,可用的方法是选取(hhh)或(hoo)晶面作衍射,此时仍可获得线性的2θ与sin^2Ψ关系,并由斜率求得应力,但应注意粗晶造成统计波动,原因在于H晶面具有最低的多重性因子,并且织构材料在某些Ψ角度下衍射强度本身就很低。

织构材料X射线应力分析的线性方程组

织构材料因弹性呈现各向异性，经典Ｘ射线残余应力分析法不再适用．借助取向分布函数（ＯＤＦ）分析法，由单晶的弹性性质按织构计权平均预估材料的宏观弹性各向异性，根据广义虎克定律获得求解所需应力－应变线性方程组．为了方便实际应用，深入讨论了该线性方程组的组建问题，导出对应任何测量方向的方程式系数均为一固定宏观试样坐标系下弹性常数张量元的线性组合，该组合系数仅与测量方向有关，而与材料本身的弹性性质及织构无关．对一些通常采用的测量方向，提供了适用于具有正交试样对称的织构材料确定方程组系数所需的数据，归纳了这些数据的取值规律．所述方法可适用于任何晶体结构对称的织构材料及三维应力状态，并可推广至正交对称外的其他试样对称的织构材料．

织构材料残余应力的ODF分析─方法的数学原理

利用Ｘ射线衍射测定材料的残余应力时，织构的存在引起材料宏观弹性各向异性，从而导致εψ－ｓｉｎ２ψ关系丧失线性．为了获取这类材料应力分析的近真应力－应变关系，必须定量地考虑材料中晶粒择优取向对宏观弹性性质的影响．近年来在织构ＯＤＦ分析法的基础上，相继提出适于织构材料应力分析的数学方法，本文详尽地阐述了这种方法的基本原理，并尽可能提供了所需数学处理的细节．所述方法也力图博采众长，以期尽量减少测试和计算的工作量．

高温超导融熔织构材料中单颗粒边界结的制备和测量

研究了从高温超导ＹＢＣＯ融熔织构材料中分离出单颗粒边界的工艺。采用聚酰亚胺材料作为绝缘层，从单颗粒上引出了电压测量引线，实现了对单颗粒边界传输特性的测量。实验观察到这类样品中的颗粒边界有不同的传输特性，包括磁通流类型和Ｊｏｓｅｐｈｓｏｎ弱连接类型。文中还对样品的成分和结构进行了分析，并讨论了出现弱连接行为的原因。对具有弱连接特性的样品的成分分析表明，在颗粒边界上金属元素的成分有一些偏离，Ｘ－衍射分析观察到除（００Ｌ）峰之外，还有（２００）峰，表明样品中有ａ轴取向的颗粒。而颗粒边界上的成分偏离以及颗粒间大角度的取向错位均可能导致弱连接行为的出现．

有织构 TiC 渗层内三维宏观应力梯度分布的研究

本文在综合研究前人理论的基础上,提出用侧倾装置的 H 晶面法或多重因子晶面法,根据所测晶面的 X 线弹性常数来测定有织构的 TiC 渗层内三维宏观内应力及三维宏观加权平均内应力梯度分布和精确测定无应力的2θ_0。本法可适用于测定各种渗层、涂层材料表面薄层内外的三维宏观内应力梯度分布。

Preparation and mechanical properties of carbon/carbon composites with high textured pyrolytic carbon matrix

Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon （C/C） composites was 1.89 g/cm3 after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.

Effect of NiAl content on phases and microstructures of TiC-TiB_2-NiAl composites fabricated by reaction synthesis

TiC-TiB2-NiAl composites were fabricated by self-propagating high temperature reaction synthesis（SHS） with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni＋Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC-TiB2-NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.

轧制铝合金的X-射线法残余应力测试

在轧制铝合金的X射线残余应力测试中,由于存在择优取向,在不同Ψ角位置参与衍射的晶面数目不同,造成不同Ψ角位置的衍射强度出现差异,影响衍射峰的θ-2θ位置的判断,进而2θ-sin2Ψ和Ip-sin2Ψ出现不同程度的震荡,造成测试结果准确度下降.文中采用"多晶面衍射法"从衍射峰形和强度分布出发,分析了轧制铝合金测试过程中不同衍射晶面随Ψ角位置衍射强度的变化,然后选择合适的峰形进行拟合.结果表明,采用"多晶面法衍射"可以保证衍射峰型和强度比,进而得到的测试结果和理论值吻合度较好,满足对轧制铝合金测试结果的要求.

Microstructure of TA2/TA15 graded structural material by laser additive manufacturing process

TA2/TA15 graded structural material（GSM） was fabricated by the laser additive manufacturing（LAM） process. The chemical composition, microstructure and micro-hardness of the as-deposited GSM were investigated. The results show that the TA2 part of exhibiting near-equiaxed grains was Widmanst？tten α-laths microstructure. The TA15 part containing large columnar grains was fine basket-weave microstructure. The graded zone was divided into four deposited layers with 3000 μm in thickness. As the distance from the TA2 part increases, the alloy element contents and the β phase volume fraction increase, the α phase volume fraction decreases and the microstructure shows the evolution from Widmanst？tten α-laths to basket-weave α-laths gradually. The micro-hardness increases from the TA2 part to the TA15 part due to the solid solution strengthening and grain boundary strengthening.

Hot deformation behaviors of 35% SiC_p/2024Al metal matrix composites

The hot deformation behaviors of 35%SiCp/2024 aluminum alloy composites were studied by hot compression tests using Gleeble-1500D thermo-mechanical simulator at temperatures ranging from 350 to 500 °C under strain rates of 0.01-10 s-1. The true stress-true strain curves were obtained in the tests. Constitutive equation and processing map were established. The results show that the flow stress decreases with the increase of deformation temperature at a constant strain rate, and increases with the increase of strain rate at constant temperature, indicating that composite is a positive strain rate sensitive material. The flow stress behavior of composite during hot compression deformation can be represented by a Zener-Hollomon parameter in the hyperbolic sine form. Its activation energy for hot deformation Q is 225.4 kJ/mol. To demonstrate the potential workability, the stable zones and the instability zones in the processing map were identified and verified through micrographs. Considering processing map and microstructure, the hot deformation should be carried out at the temperature of 500 °C and the strain rate of 0.1-1 s-1.

Microstructure stability of Ti_2Al N/Ti-48Al-2Cr-2Nb composite at 900 °C

Microstructure stability of in situ synthesized Ti2AlN/Ti-48Al-2Cr-2Nb composite during aging at 900 ℃ was investigated by XRD, OM and TEM, and the unreinforced Ti-48Al-2Cr-2Nb alloy was also examined for comparison. The result showed that in the TiAl alloy,α2 lamellae thinned and were broken down, and became discontinuous with increasing aging time. The decomposition ofα2 lamella toγ which was characterized by parallel decomposition and breakdown ofα2 lamellae led to the degradation of the lamellar structure. While in the composite, lamellar structure remained relatively stable even after aging at 900 ℃ for 100 h. No breakdown ofα2 lamellae except parallel decomposition and precipitation of fine nitride particles was observed. The better microstructural stability of the composite was mainly attributed to the precipitation of Ti2AlN particles at theα2/γ interface which played an important role in retarding the coarsening of lamellar microstructure in the matrix of composite.

Prediction of the thermo-elastic properties of knitted structural composites using FEM

It is a very important and complex task to estimate the thermo-elasticproperties of a textile structural composite. In this paper, the finite element method (FEM) wasused for the prediction of the orthotropic thermo-elastic properties of a composite reinforced byglass fiber knitted fabric. In order to define the final 3-D configuration of the loop reinforcingstructure, the interactions between the adjacent loops, the large displacement and the contactelements without friction were considered. The values predicted were compared with the experimentalresults.

放电等离子烧结制备(ZnO)_mIn_2O_3织构材料及其热电性能研究

以Zn(OH)2和In2O3为原料,用放电等离子烧结(SPS)技术制备了层状结构的(ZnO)mIn2O3(m=5,7,9)织构热电材料。通过XRD、SEM以及ZEM表征样品的物相、显微组织和电输运性能,分析了m值和烧结温度的影响机制。结果表明,(ZnO)mIn2O3(m=5,7,9)块体材料在平行于压力方向沿(00l)择优取向,呈层状结构特征。固定烧结温度为1323K时,(ZnO)7In2O3样品在773K取得最大功率因子1.88×10-4W·m-1K-2。优化(ZnO)9In2O3样品的烧结温度,发现降低烧结温度增加了Seebeck系数,1223K烧结时在773K取得最大功率因子2.2×10-4W·m-1K-2。

Preparation and Properties of Antibacterial Lyocell Fibers Containing Chitosan Derivative

The O-carboxymethyl chitosan sodium salt, NaCMCh, was initially synthesized and analyzed with better antibacterial activity than chitesan. Then NaCMCh was dissolved in the N-mcthylmorpholine-N-oxide, NMMO, solution with cellulose for spinning of the lyocell fiber. The results showed that the lyocell fibers modified with over 2 wt% NaCMCh has good antibacterial activity in against the E. coli and with NaCMCh content below 6 wt% has considerable mechanical properties.

A Novel Aqueous Polyurethane Containing Short Fluoroalkyl Chains:Synthesis and Application on Cotton Fabrics

As very useful superficial mediflcation agents, the common long perfluoroalkyl -- containing agents are facing the ecological problems, such as persistence, bioacumulatlen, and/or toxicity in the environment. In order to overcome the problems, we designed and synthesized a polyether dioi containing short perfluoroaikyl side chains, which was condensed with diisocyanate to form fluorine-containing aqueous polyurethane. This aqueous polyurethane was applied on cotton fabrics by conventional pad-dry-cure process. The treated cotton fabrics showed good water repellent property with the contact angle reached 131°, and also IXBSessed good washing durability.

Die sinter bonding in air using copper formate preform for formation of full-density bondline

Pressure-assisted sinter bonding was performed in air at 250−350℃ using a preform comprising copper formate particles to form a bondline that is sustainable at high temperatures.H2 and CO generated concurrently by the pyrolysis of copper formate at 210℃ during the sinter bonding removed the native oxide and other oxides grown on bulk Cu finishes,enabling interface bonding.Moreover,Cu produced in situ by the reduction of Cu(II)accelerated the sinter bonding.Consequently,the bonding achieved at 300−350℃ under 5 MPa exhibited sufficient shear strength of 20.0−31.5 MPa after 180−300 min of sinter bonding.In addition,an increase in pressure to 10 MPa resulted in shear strength of 21.9 MPa after an extremely short time of 30 s at 250℃,and a near-full-density bondline was achieved after 300 s.The obtained results indicate the promising potential of the preform comprising copper formate particles for high-speed sinter bonding.

Effects of laser surface melting on crystallographic texture, microstructure, elastic modulus and hardness of Ti-30Nb-4Sn alloy

The biocompatibility of orthopedic implants is closely related to their elastic modulus and surface properties.The objective of this study was to determine the effects of cold rolling,recrystallization and laser surface melting(LSM)on the microstructure and mechanical properties of a biphase(α″+β)Ti-30Nb-4Sn alloy.X-ray diffraction(XRD)texture analysis of the cold-rolled substrate revealed the[302]α″//ND texture component,while analysis of the recrystallized substrate showed the[302]α″//ND and[110]α″//ND components.Theβ-phase texture could not be directly measured by XRD,but the presence of the[111]β//ND texture component was successfully predicted by considering the orientation relationship between theα″andβphases.Nanoindentation measurements showed that the elastic modulus of the cold-rolled substrate(63GPa)was lower than that of the recrystallized substrate(74GPa).Based on the available literature and the results presented here,it is suggested that this difference is caused by the introduction of crystal defects during cold deformation.The combined nanoindentation/EBSD analysis showed that the nanoindentation results are not affected by crystal orientation.LSM of the deformed alloy produced changes in hardness,elastic modulus and crystallographic texture similar to those produced by recrystallization heat treatment,creating a stiffness gradient between surface and substrate.