Evaluation of the mechanical properties of conventionally-cast Al matrix composites reinforced by quasicrystalline Al-Cu-Fe particles using continuous ball indentation technique

Room temperature mechanical properties of the Al/(AlCuFe)_p and Al₉₆Cu₄/(AlCuFe)_p cast composites were estimated from uniaxial compressive test and continuous ball indentation technique. Values of the Young’s modulus and yield stress determined from continuous ball indentation tests were slightly overestimated, suggesting a surface effect on the mechanical properties. However, it was shown that the Al-Cu-Fe particles provided a significant increase of the elastic modulus, yield stress, and strain hardening, especially in the range up to 10% volume fraction of reinforcements. Also, determination of the hardness by continuous-ball-indentation tests revealed a strong influence of the matrix strength on the mechanical properties of the conventionally cast composites.     

OPTIMAL DESIGN PROCEDURE BASED ON VISCOPLASTIC MATERIAL BEHAVIOUR

1.IntroductionSafety,functionality,protectionofenvironmentandlowpricemaybenumberedasmayorreasonsformakingofanoptimalproduct.Ontheotherhandoptimalproductmaybedonebyconcurrentlyutilizingalloftherelevantinformation,methods,computerperformances,manufacturingpossibilitiesandofcourseknowledgepotential.Themaintaskoftheoptimalprocedureinthedesignprocessaswellasinthemanufac-turingprocessistofindthebestcombinationbetweentheobjectivefunctionandconstrains.Theobtainedproductwillbeoptimalasthemathematicalid…     

Synergism in the wetting properties of ternary surfactant mixtures

It has been shown that ternary surfactant synergism can be predicted on the basis of nonideality parameters of binary subsystems derived from advancing contact angles. Studies with appropriate surfactant mixtures of glucamides, ether sulfates, secondary alkane sulfonates, and alkylamidopropyl betaines were performed on substrates of different polarity.     

Characterization of Pheromone Blend for Grapevine Moth, Lobesia botrana by Using Flight Track Recording

The behavioral responses of Lobesia botrana males to calling females, pheromone gland extracts, and synthetic sex pheromones were recorded in a wind tunnel. Gland extracts and synthetic pheromones were released from a pheromone evaporator. The numbers of males reaching the source and their flight tracks in response to calling females and pheromone gland extracts were compared to those of synthetic blends. Upwind flights to natural sex pheromone were straighter and faster than to a three-component blend of (E)-7,(Z)-9-dodecadienyl acetate (E7,Z9–12:Ac), (E)-7,(Z)-9-dodecadien-1-ol (E7,Z9–12:OH), and (Z)-9-docecenyl acetate (Z9–12:Ac) (100:20:5). The optimum ratio of E7,Z9–12:OH and Z9–12:Ac to E7,Z9–12:Ac was found to be 5% and 1%, respectively. An additional seven compounds identified in the sex pheromone gland were investigated for their biological activity. Two unsaturated acetates, i.e., (E)-9-dodecenyl acetate (E9–12:Ac) and 11-dodecenyl acetate (11–12:Ac), increased the number of males reaching the source as well as straightness, linear velocity, and decreased the track angle of upwind flight. Optimum response was obtained by releasing 10 pg/min E7,Z9–12:Ac in a mixture with 0.5 pg/min E7,Z9–12:OH, 0.1 pg/min Z9–12:Ac, 0.1 pg/min E9– 12:Ac and 1 pg/min 11-12–Ac. The saturated acetates previously identified in the female glands were biologically inactive.     

Crystallization and melting behaviors of poly(trimethylene terephthalate)

The crystallization and melting behaviors of poly(trimethylene terephthalate) (PTT) have been studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and solid-state NMR. At certain crystallization temperatures (T_c) for a given time, the isothermally crystallized PTT exhibits two melting endotherms, which is similar to that of PET and PBT. At higher crystallization temperature (T_c = 210 °C), the low-temperature endotherm is related to the melting of the original crystals, while the high-temperature endotherm is associated with the melting of crystals recrystallized during the heating. The peak temperatures of these double-melting endotherms depend on crystallization temperature, crystallization time, and cooling rate from the melt as well as the subsequent heating rate. At a low cooling rate (0.2 °C/min) or a high heating rate (40 °C/min), these two endotherms tend to coalesce into a single endotherm, which is considered as complete melting without reorganization. WAXD results confirm that only one crystal structure exists in the PTT sample regardless of the crystallization conditions even with the appearance of double melting endotherms. The results of NMR reveal that the annealing treatment increases proton spin lattice relaxation time in the rotation frame, T_1ρ ^H, of the PTT. This phenomenon suggests that the mobility of the PTT molecules decreases after the annealing process. The equilibrium melting temperature (T _m ^o ) determined by the Hoffman-Weeks plot is 248 °C.     

L-苹果酸中富马酸钙与苹果酸钙溶解动力学

采用反应分离耦合技术以富马酸钙为底物生产Ｌ－苹果酸是目前该产品生产的最佳方式,因此,研究该工艺过程中底物富马酸钙与产物苹果酸钙的溶解行为显得十分重要。详细考察了底物富马酸钙、产物苹果酸钙的溶解过程,讨论了温度、ｐＨ对溶解过程的影响,得出不同温度下溶解的Ｃ－ｔ曲线及动力学方程,结果如下。底物富马酸钙溶解动力学方程：４０℃：ｄＣ／ｄｔ＝２．７６１×１０－２（０．０９１２６－Ｃ）０．５６８２２０℃：ｄＣ／ｄｔ＝２．８７８×１０－３（０．０７５２２－Ｃ）０．２６７９产物苹果酸钙溶解动力学方程：４０℃：ｄＣ／ｄｔ＝４．０４１×１０－３（０．０６７５２－Ｃ）０．４０７１２０℃：ｄＣ／ｄｔ＝９．０９６×１０－３（０．０５１９５－Ｃ）０．７６７６     

三（2,2—二溴甲基—3—溴丙基）磷酸酯对聚丙烯阻燃及流变性的影响

以自行合成的三（２,２－二溴甲－３－溴丙基）磷酸酯（ＴＤＢＰ）为阻燃剂,研究了ＴＤＢＰ阻燃聚丙烯的阻燃和力学性能。采用Ｌｎｓｔｒｏｎ３２１１流变仪测定和分析了ＴＤＢＰ和ＴＤＢＰ／Ｓｂ２Ｏ３阻燃聚丙烯在不同阻燃剂用量及温度下的流变行为。结果表明,ＴＤＢＰ与Ｓｂ２Ｏ３对聚丙烯的阻燃具有明显的协同阻燃效应。ＴＤＢＰ和ＴＤＢＰ／Ｓｂ２Ｏ３阻燃聚丙烯的流变行为均表现出剪切变稀的非牛顿流体特性,其流变行为受温     

PPO／PA6／弹性体多相共混物的流变行为

采用Ｉｎｓｔｒｏｎ３２１１毛细管流变仪对不同用量的ＳＥＢＳ和ＰＯＥ－ｇ－ＭＡＨ两种弹性体增韧改性的ＰＰＯ／ＰＡ６多相共混物的流变行为进行了测试。对比了两种弹性体在不同温度和剪切速度下对共混体系表观粘度的影响。     

形状记忆晶相/铜基非晶复合材料的组织和微观力学行为研究

本文采用悬浮熔炼-水冷铜模吸铸法制备Cu50Zr42Al8锥形试样,研究了合金不同直径处的组织和微观力学行为,分析了尺寸效应和裂纹自愈合行为。结果表明,复合材料组织中包括非晶基体相、金属间化合物AlCu2Zr相、奥氏体B2-ZrCu相和热致马氏体 B19’-ZrCu相。纳米压痕结果表明,单一非晶结构的试样心部硬而表面较软,呈现越小越软趋势,而较大尺寸的非晶复合材料由于析出相的存在,心部软而表面较硬。形状记忆晶相由TRIP效应对非晶基体增强增韧,而AlCu2Zr相析出使基体脆化。经150 oC 10mins退火后,微观压痕产生的裂纹表现出自愈合行为。加载时,形变诱导B2奥氏体向B19’马氏体相转变并伴随着体积的膨胀,而高于逆转变温度退火,B19’转变为B2相,体积收缩并驱动裂纹愈合。     

球磨纳米结构Fe40Al合金粉末及其冷喷涂沉积行为研究

目的研究冷喷涂用纳米结构Fe40Al合金粉末的球磨制备工艺及其在不同基体表面的冷喷涂沉积行为。方法以Fe粉、Al粉为原料,按照Fe-40Al进行配比混合,采用行星式球磨机制备纳米结构Fe40Al合金粉末,在不同硬度基体表面(不锈钢、低碳钢、纯铜及锡)冷喷涂沉积单个Fe40Al合金粉末颗粒。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM),分析球磨过程中Fe40Al合金粉末的组织结构演变规律、粉末颗粒在不同基体表面的碰撞变形行为及沉积特性。结果球磨过程中,随着球磨时间的延长,Al扩散进入Fe晶格形成纳米结构Fe(Al)固溶体,球磨36 h后,Fe40Al合金粉末的晶粒尺寸约为35 nm,平均颗粒尺寸约为20μm,内部为精细层状结构。纳米结构Fe40Al合金粉末在硬度较高的不锈钢和低碳钢基体上沉积时,粉末颗粒发生强塑性变形而基体变形量较小,颗粒和基体间的结合较弱,沉积效果较差;当在硬度较低、塑性较好的Cu基体上沉积时,基体与粉末颗粒同时发生塑性变形,颗粒和基体间的结合较强,沉积效果最好;在硬度最低的Sn基体上沉积时,基体发生强烈的塑性变形且出现部分熔化,但颗粒几乎没有变形,且颗粒与基体间的结合很弱,沉积效果最差。结论采用球磨工艺可制备出适合冷喷涂用的纳米结构Fe40Al合金粉末,随着球磨时间的延长,粉末晶粒尺寸减小,硬度增加。基体种类对纳米结构Fe40Al合金粉末的冷喷涂沉积行为影响显著,基体硬度过高或过低均不利于粉末颗粒沉积,基体与粉末颗粒同时发生塑性变形有利于增强颗粒与基体间的界面结合,从而改善沉积效果。