Sn-Pb合金枝晶生长的同步辐射X射线衍射增强成像研究

用北京同步辐射光源X射线衍射增强成像法对Sn-Pb金属合金的结晶过程进行实时成像研究,成功地获得枝晶生长行为及形貌演变的系列动态图像,为研究金属合金结晶理论提供直接的实验数据.实验观察到接近共晶成分的Sn-50wt.%Pb合金,在一定的温度梯度和冷却速率下呈现先等轴晶后柱状晶形貌生长.同步辐射X射线衍射增强成像技术为原位研究不透明的金属合金枝晶生长过程提供了崭新的实验手段,为验证或完善金属合金结晶过程的微观动力学模型提供了有效途径.     

高能激光束引燃自蔓延合成共晶Al/Cu合金组织结构及性能

针对共晶Al/Cu系粉末压坯,采用激光引燃自蔓延烧结技术(SHS)制备烧结Al/Cu合金,用扫描电镜(SEM)、金相显微镜(OM)、X射线衍射(XRD)以及布氏硬度计研究了压制压力和激光功率与作用时间对烧结合金微观结构、致密性及硬度的影响.研究结果表明,随着激光功率提高和作用时间延长,烧结合金组织均匀性得到提高,相对密...     

The transformation behavior of a U-16.4 at % Nb-5.6 at % Zr alloy

The isothermal transformation kinetics of a γ-phase U-16.4 at % Nb-5.6 at % Zr alloy have been studied by resistometric techniques between 130 and 590° C. Three distinct regions of transformation were observed. Above 420° C the transformation proceeded by nucleation and growth and progressed to the equilibrium $\text{α + γ}{}_2$ phases. Aging at temperatures between 270 and 400° C resulted in the appearance of a transition $\text{α}{}^{\mathrm{″}}$ monoclinic phase that remained stable after even 7 days of aging at 380° C. Aging below 250° C produced a tetragonal $\text{γ}{}^0$ phase. A negative temperature coefficient of resistance is observed at temperatures below 400° C when the material is quenched from a 900° C anneal. It is suggested that 400° C represents an athermal γ to $\text{γ}{}^{\mathrm{<mtext>S</mtext>}}$ transformation and that the negative resistance coefficient results from a continual change of lattice parameters of $\text{γ}{}^{\mathrm{<mtext>S</mtext>}}$ with decreasing temperature.     

Development of an oxygen sensor for molter 44.5% lead-55.5% bismuth alloy

A potentiometric sensor for measuring oxygen activity in molter 44.5% lead-55.5% bismuth alloy is under development. Three parts form this sensor: an In/In₂O₃ reference electrode, a ZrO₂/Y₂O₃ solid electrolyte, and a molybdenum working electrode. The oxygen partial pressure in the melt is calculated applying the Nernst equation to the potential difference measured by the sensor. The minimum oxygen partial pressure detected by this sensor is 10⁻⁴⁰ bar. The sensor has been calibrated with the following metal/metal oxide mixtures: Pb-Bi/PbO, Pb/PbO, Sn/SnO₂, and Bi/Bi₂O₃. Reproducible measurements of the oxygen pressure of PbO formation have been obtained. The sensor performance has been evaluated in 99.999% N₂ and air (20% O₂) environments.     

Possible field-ion microscopical investigation of the behavior of interstitial atoms in tungsten and A W-1.5% ThO2 alloy

Translated from Atomnaya énergiya, Vol. 69, No. 1, pp. 46–47, July, 1990.     

Creep damage behaviour of 12% Cr steel

The creep damage behaviour of different batches of 12% Cr steel X 20 CrMoV 12 1 was investigated. An overall damage map as function of consumed life fraction was developed. This classification is being compared to that of TRD 508 guideline. Generally in X 20 CrMoV 12 1 cavitation and microcrack formation is shifted to higher life fractions. Recommendations for procedures with power plant components are given.     

Textural nonuniformity in sheets of Zr-2.5% Nb alloy

Moscow Engineering Physics Institute. Translated from Atomnaya Énergiya, Vol. 72, No. 2, pp. 181–184, February, 1992.     

Irradiation behavior of atomized U–10wt.% Mo alloy aluminum matrix dispersion fuel meat at low temperature

In order to examine the in-reactor behavior of very-high-density dispersion fuels for high flux performance research reactors, U–10wt.% Mo alloy dispersions in an aluminum matrix have been irradiated at low temperature in the Advanced Test Reactor (ATR). The alloy fuel dispersant was produced by a centrifugal atomization process. The fuel shows stable in-reactor irradiation behavior to a fission density of 5×10²⁷ m⁻³ at an irradiation temperature of 65 °C. The fuel–matrix interaction layer growth rate is similar to that observed in uranium-silicide fuels. The fuel particles have a fine and a relatively narrow fission gas bubble size distribution. There appears to be features in the microstrucure that are the result of segregation of the microstructure in to molybdenum rich and depleted regions on solidification.