从动圆锥齿轮毛坯吃刀现象分析

对20CrNi3A的从动圆锥齿轮进行了硬度、化学成分、金相组织等进行了分析。结果表明:吃刀现象是由于在组织中存在着硬质相(马氏体相),导致加工时严重吃刀、机床颤动剧烈等现象的发生。     

近β钛合金高温压缩变形过程中流变软化行为研究进展

综述了近β钛合金高温压缩变形过程中流变软化行为的影响因素、流变软化机制及其分析方法以及基于流变软化机制的本构方程的发展,重点分析了变形工艺参数以及原始微观组织对流变软化行为的影响规律,此外,讨论了动态回复、动态再结晶、变形热等软化机制对软化现象的贡献,并提出了近β钛合金高温变形过程中关于流变软化现象亟待解决的问题,指出定量化及物理模型化是未来近β钛合金高温变形过程中流变软化现象的重要发展方向。     

Static and dynamic deformation mechanisms of a high-density polyethylene having rownucleated crystalline texture of a-axis orientation as observed by orientation distribution function of crystallites

The rheo-optical properties of a high-density polyethylene having a row-nucleated crystalline texture of a-axis orientation were investigated in the machine direction (MD) and transverse direction (TD) of fabricating the specimen. The tensile complex dynamic compliance function $\text{J1}$ displays two dispersions designated as the α₂ and α₂ mechanical retardation processes with activation energies of about 21 and 35 kcal mol^?1, respectively, for both MD and TD specimens, and the complex dynamic stress-optical coefficient function $\text{M1}$ exhibits a single discrete dispersion designated as the α optical retardation process with an activation energy of about 24 kcal mol^?1 for both specimens over the same frequency and temperature ranges as those covered for the dynamic mechanical measurements. The real and imaginary components of $\text{M1}$ converge from positive values to almost zero at the highest frequencies and lowest temperatures covered for both specimens, with the exception of the real component of the MD specimen which converges to a small but definitely negative value. The analysis of this anomalous behaviour of the MD specimen in terms of the optical retardation time spectrum has ascribed the negative convergence to a negative form birefringence that arises from a dynamic lamellar splaying or bending process responding in phase with the dynamic bulk stress. The dynamic X-ray diffraction studies have revealed the α optical dispersion and possibly the α mechanical dispersion to be mostly attributed to the crystal orientation dispersions involving intralamellar shearing processes, i.e. detwisting and tilting processes of the lamellar segments for the MD and TD specimens, respectively. The optical dispersion, if any, associated with the lamellar splaying or bending process may be expected at higher frequencies or lower temperatures than those covered here to assign the β mechanical dispersion to the interlamellar shearing process.     

复Banach空间上推广的Roper-Suffridge算子的性质

讨论复Banach空间上两类推广的Roper-Suffridge算子,证明该算子保持强β型螺形映照、强α次殆星映形照、α次强β型螺形映照及α次殆β型螺形映照的性质,并作为特殊情况包含了已有的结论.     

Re-examination of the β→γ transformation of Ca2SiO4

Dicalcium silicate finds applications in different fields (cement, bio-ceramics, refractories). In the case of Portland cement, its interest is its lower sintering temperature compared to tricalcium silicate and therefore an interesting compound for low CO₂ cements. Dicalcium silicate goes through different polymorphic forms, namely α, α'_H, α'_L, β and γ, as the temperature decreases. In theory, only the γ-phase is stable at room temperature. In a polycrystalline material, the different polymorphs can co-exist depending on several factors (sintering conditions, presence of impurities, grain size) and the interpretations given in the literature are sometimes contradictory. For cement applications, only the α, α' or β polymorphs react with water to give hydrates while γ does not. Therefore, this paper focuses specifically on the effect of grain size on the β to γ transformation. We also propose that the transformation is semi-reconstructive and not martensitic as suggested by some authors.     

Ti-25 Nb-25 Ta合金拉伸变形过程中｛332｝〈113〉变形孪晶的EBSD研究

本文利用EBSD技术对亚稳β型Ti?25Nb?25Ta合金室温拉伸变形过程中｛332｝〈113〉变形孪晶的演变趋势及交叉现象进行了研究。结果表明：随着变形量的增大，孪晶宽度不断增加，孪晶形态由变形初期的平直细条带状逐渐变为宽窄不一的条带状，至变形末期部分孪晶呈破碎状，孪晶界严重扭曲变形。多数晶粒内产生两种以上｛332｝〈113〉孪晶变体，部分孪晶能穿越晶界继续生长，某些初次孪晶内部有二次｛332｝〈113〉孪晶产生。不同变体孪晶间易发生交叉现象。不同｛332｝〈113〉孪晶变体的交叉作用导致交叉区域出现较大的局部晶格畸变，晶格畸变主要集中于孪晶内部，且交叉界面处的晶格畸变程度最为严重。交叉作用的结果是交叉区域的晶体相对于不同孪晶变体和基体的取向都发生一定程度的改变。     

双杂原子Cr-Co-β沸石的合成及其苯乙烯氧化性能

采用水热法在Si O2-Cr2O3-Co O-(TEA)2O-H2O-NH4F体系中((TEA)2O:氧化四乙基铵)合成了具有良好结晶的双杂原子Cr-Co-β沸石,通过XRD,FTIR,UV-Vis,TG-DTG,SEM等技术对试样的结构进行了表征。以H2O2为氧化剂氧化苯乙烯为探针反应,考察了Cr-Co-β沸石的催化活性,研究了溶剂种类、金属配比、H2O2与苯乙烯的摩尔比、催化剂用量、反应时间和反应温度等对反应的影响。实验结果表明,以丙酮为溶剂,以n(Si)∶n(Cr+Co)=20的Cr-Co-β沸石为催化剂,在催化剂用量60 mg、苯乙烯用量17 mmol、H2O2与苯乙烯的摩尔比3、反应温度70℃、反应时间7 h的条件下,苯乙烯转化率为88.4%,苯甲醛选择性为85.3%,环氧苯乙烷选择性为10.7%,苯甲醛收率为75.4%。     

甲基环糊精-对叔丁基酚包络物电化学研究及应用

本文主要研究了甲基-β-环糊精-对叔丁基酚包络物的极谱行为。在0.05mol/L的KCl底液中,甲基-?-环糊精-对叔丁基酚包络物在2.5次微分极谱仪上产生还原波,其峰电位为-0.85V(vs.SCE),其峰电位随对叔丁基酚浓度的增大而负移,峰形稳定;并且峰电流与对叔丁基酚浓度在1.0×10-5mol/L~6.0×10-5mol/L之间呈良好的线性关系,检测下限为1.0×10-5mol/L。     

硫酸亚铁-β-环糊精包合作用的研究

采用饱和水溶液法制备硫酸亚铁-β-环糊精包合物,紫外分光光度法表征了包合物的形成,并用循环伏安法进一步证实β-环糊精和硫酸亚铁的主客体包合作用。最后采用紫外分光光度法确定了硫酸亚铁-β-环糊精包合物的包合比,并测定了包合物的包合常数,结果表明,β-环糊精与硫酸亚铁可形成包合物,包合比为1：1,包合常数为57．74L/mol。