Prediction of hot deformation behaviour of Fe-25Mn-3Si-3Al TWIP steel

Hot deformation behaviour of Fe-25Mn-3Si-3Al twinning-induced plasticity (TWIP) steel was investigated by hot compression testing on Gleeble 3500 thermo-mechanical simulator in the temperature range from 800 to 1100 °C and at strain rate range from 0.01 to 5 s⁻¹, and the microstructural evolution was studied by metallographic observations. The results show that the true stress-true strain curves exhibit a single peak stress at certain strain, after which the flow stresses decrease monotonically until the end of deformation, showing a dynamic flow softening. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be predicted by the Zener-Hollomon (Z) parameter in the hyperbolic sine equation with the hot deformation activation energy Q of 405.95 kJ/mol. The peak and critical strains can also be predicted by Z parameter in power-law equations, and the ratio of critical strain to peak strain is about 0.7. The dynamic recrystallization (DRX) is the most important softening mechanism for the experimental steel during hot compression. Furthermore, DRX procedure is strongly affected by Z parameter, and the decreasing of Z value leads to more extensive DRX.     

Physicochemical properties and photocatalytic hydrogen evolution of TiO2 films prepared by sol–gel processes

Anatase TiO₂ films were obtained on glass substrates using a sol–gel method using titanium isopropoxide as a precursor. The thickness of the film was about 140 nm for one coating, and the thickness is controlled by the number of coating cycles. The spectra of UV-VIS absorption indicated that the absorption edge of the TiO₂ films is ca. 385 nm, corresponding to the band gap energy of 3.20 eV. We obtained TiO₂ films having a high activity for the hydrogen evolution from photocatalytic water cleavage. By loading with 0.3 wt% Pt rate of hydrogen production increases. No influence of film thickness and calcination temperature on the photocatalytic property is observed.     

Effects of load and thermal conditions on Pb-free solder joint reliability

Reliability of lead-free solder joints has been a hot topic widely debated in the electronic industry. Most published data indicate that a change to lead-free soldering has the potential benefit of more reliable solder joints than the current Sn-Pb eutectic solder joints. However, in reality many mechanical, metallurgical, thermal, and environmental factors affect the service reliability of solder joints. This paper tries to shed some light on the effects of mechanical loading and thermal conditions on solder joint reliability. These conditions are determined not only by external environments but also by the solder alloy itself and the joint geometry. Analyses with first principles are carried out on solder joints of both areal array and peripheral packages. Effects on fatigue life of solder joint geometry, thermal and mechanical characteristics of components and substrate materials, and application conditions are discussed. The analysis helps explain why lead-free solder joints may not be more reliable in certain application conditions than the current Sn-Pb eutectic solder joints.     

紫外激光辐照非纯7-DHC研究

本文报道用KrF准分子激光和N_2分子激光分别辐照含杂质的7-去氢胆留醇合成维生素D_3的实验研究。维主素D_3的前身P_3的转化率～63％。     

分光光度法测定聚氨酯中微量异氰酸酯基

研究了分光光度法测定聚氨酯中微量异氰酸酯基的方法。以N,N-二甲基甲酰胺(DMF)为溶剂,在冰醋酸(HAc)存在下,异氰酸酯基与二甲氨基苯甲醛(DMAB)形成有色化合物,该有色化合物的最大吸收波长为430 nm,表观摩尔吸光系数ε=2.80×104 L·mol-1·cm-1。在430 nm波长下,NCO基团浓度在0-20μg/10 mL范围内符合比尔定律。该方法用于聚氨酯中微量游离异氰酸酯基的测定,相对标准偏差小于5％,具有简便、快速、准确、可靠的特点。     

An analytical model for the interaction between an insoluble particle and an advancing solid/liquid interface

In this article, the behavior of particles in front of an advancing solidJliquid interface was analyzed. In the analytical model presented, the critical velocity for the transition from particle pushing to engulfment by the interface was calculated as a function of relevant material parameters and processing variables. In particular, the effect of the difference in the thermal properties of the particle and the matrix on the particle/interface interaction was examined. It was demonstrated that the presence of particles could destabilize the interface which, in turn, affected the behavior of particles at the interface. Based on the analysis, a particle behavior map was constructed to illustrate the complex particle behaviors in different material systems under various growth conditions. Theoretical predictions were compared against experimental results obtained in transparent organic materials as well as in metallic systems. The relevance of these observations to the melt processing of particulate-reinforced metal matrix composites (MMCs) was discussed. Formerly Assistant Research Engineer, The University of Alabama, is now Manufacturing Engineer     

CrNiMo钢在不同氧气含量气氛中的高温摩擦磨损性能

利用QG-700型摩擦磨损试验机,研究与H96黄铜配副的CrNiMo在不同氧气含量环境中的高温摩擦磨损性能,并利用扫面电镜对磨损表面进行表征。结果显示,在较低速度和载荷条件下,气氛环境中氧气含量的增加对与黄铜配副的CrNiMo钢摩擦磨损性能影响较小;在较高速度和载荷条件下,CrNiMo钢摩擦因数与磨损率随气氛环境中氧气含量的增加而减小。随气氛中氧气含量的增加,在摩擦接触表面形成不同的表面膜,使CrNiMo钢的磨损机制发生变化,由黏着磨损为主转变为黏着磨损和氧化磨损共同作用然后到氧化磨损。     

改革开放30年汽车橡胶减振行业的发展变迁

一、橡胶减振零部件与汽车NVH性能 汽车的NVH（Noise,Vibration and Harshness）特性是汽车的五大重要性能之一（另外四个性能指标为：安全、节能、环保和可靠性）。随着汽车的高速化、轻量化设计和人们对汽车舒适性要求的不断提高,汽车在NVH方面的问题越来越突出并被日益重视。橡胶减振元件是汽车减振系统中的重要减振元件．对汽车的NVH性能有重要的影响。汽车的NVH性能是通过控制汽车中有关零部件及相关子系统的振动与噪声而得以实现的．它给汽车用户的感受是最表面和直接的。汽车的NVH特性是汽车行业与相关汽车零部件行业关注的综合性问题之一。     

不确定目标的多解规划研究--以北京大环文化产业园的预景规划为例

预景规划被认为是当今处理动态的、复杂的、非线性的环境的最好的规划方法之一。欧美生态学家和景观规划师早在20世纪80年代就将此方法运用于环境规划和管理之中。本文以大环文化产业园的预景规划为例,探索从一个模糊的不确定目标通过多次头脑风暴和不断搜寻,进而寻找到若干个相对清晰的目标的多解规划的过程与方法。     

紫红薯渣、膳食纤维和漂白膳食纤维物化特性分析

对紫红薯渣、膳食纤维和漂白膳食纤维的物化特性进行了测试与分析。结果表明,紫红薯膳食纤维的水合性质与紫红薯渣相比差异极显著(P<0.01),H2O2处理极显著地降低了紫红薯膳食纤维的水合性质;酶法和H2O2处理降低了样品吸附胆酸钠的能力,但提高了吸附亚硝酸钠的能力;紫红薯渣、膳食纤维和漂白膳食纤维的水合性质分别为:膨胀力4.36、14.3、9.30 mL/g,持水力2.65、8.39、6.49 g/g,结合水力1.89、3.12、2.05 g/g;紫红薯渣、膳食纤维和漂白膳食纤维的阳离子交换能力分别为0.12、0.88、0.48 mmol/g;紫红薯渣、膳食纤维和漂白膳食纤维吸附胆酸钠的能力分别为35.03、24.12、17.84 mg/g;紫红薯渣、膳食纤维和漂白膳食纤维吸附NaNO2的能力分别为1.08、2.81、2.98 mg/g。结果显示,紫红薯膳食纤维是一种天然的优质膳食纤维,具有广阔的应用前景。