Microstructure and mechanical properties of fine grained uranium prepared by ECAP and subsequent intermediate heat treatment

The microstructure and mechanical properties of fine grained uranium prepared by equal channel angular pressing (ECAP) and subsequent intermediate heat treatment were investigated systematically by the confocal laser scanning microscope (CLSM), electron backscatter diffraction (EBSD) and split Hopkinson pressure bar (SHPB). The results show that the initial coarse grained uranium was refined from about 1000 to 6.5 μm prepared by ECAP at 3 passes and subsequent heat treatment, and the corresponding dynamic yield strength increased from 135 to 390 MPa. For the ECAPed uranium samples, the relationship between grain size and yield strength could be described by classical Hall–Petch relationship, and the fitting Hall–Petch relationship for the fine grained uranium samples prepared by ECAP was drawn.     

Effect of soaking medium on the physicochemical properties of parboiled glutinous rice of selected Laotian cultivars

The effect of various soaking mediums, viz. water (control), 3% NaCl and 0.2% acetic acid, and without soaking on the physicochemical properties of parboiled selected glutinous (TDK8 and TDK11) and non-glutinous (Doongara) was investigated in the present study. Results showed that the chemistry of soaking had a significant effect on the head rice yield (HRY), grain hardness, crystallinity, color, pasting and thermal properties, textural attributes, and glycemic index of these rice varieties. Soaking with NaCl and acetic acid significantly increased the grain hardness and HRY than control and without soaking treatments. Acetic acid and NaCl soaking significantly affected crystalline regions of starch resulting in reduced crystallinity in X-ray diffraction analysis and thermal endotherms in DSC analysis. NaCl soaking induced swelling of starch granules resulting in high peak and final viscosities. However, acetic acid restricted swelling resulting in reduced peak and final viscosities. NaCl and acetic acid soakings also resulted in increased hardness and adhesiveness of cooked grains than normal water soaked and un-soaked parboiled rice samples. Interestingly, change in textural attributes was prominent in parboiled glutinous rice. The color difference value for fresh parboiled samples was significantly lower for acetic acid soaked samples compared to NaCl soaked and un-soaked samples probably due to bleaching effect of acetic acid. Moreover, parboiling also resulted in significant reduction in glycemic index of glutinous rice. These findings revealed the potential application of parboiling with modified soaking techniques to improve the grain quality.     

Fine equiaxed dendritic structure of a medium carbon steel cast using pulsed magneto-oscillation melt treatment

The application of a pulsed magneto-oscillation (PMO) technique during the solidification of a commercial high melting point medium carbon steel ingot (φ140 mm 9 450 mm) produced fully equiaxed grains in the cast ingot, indicating that the PMO process significantly promotes heterogeneous nucleation near the solid-liquid interface. The vigorous convection induced by PMO forced the partly solidified grains to move from the solid-liquid interface and became randomly distributed throughout the melt, which resulted in the formation of uniformly sized equiaxed dendrites throughout the whole ingot. Building on the developed nucleation mechanism and a flow field simulation of pure aluminum, a PMO-induced grain refinement model for steel is proposed.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-017-0206-5     

The effects of Zr and Ti on the microstructure and tensile properties of Al–Cu–Mg aluminium alloy

The effects of Al–5Ti–1B and Al–15Zr master alloys on the structural characteristics and tensile properties of Al–4.5Cu–0.3Mg aluminium alloy were studied. Al–5Ti–1B was found to be more effective than Al–15Zr in grain refining of the alloy. It could be seen that average grain size reduces from 570 to 260?μm when 0.01?wt-% Ti addition; additionally, while different amounts of Ti and Zr were added to the alloy, the dendritic structure changes from long dendrite to rather rosette-like morphology. Furthermore, tensile testing of cast specimens revealed that ultimate tensile strength (UTS) of the cast alloy increases from 241 to 283 and 260?MPa after adding the optimum amount of Ti and Zr containing master alloys, respectively. Moreover, UTS values of T6 heat-treated specimens also showed 73 and 61% improvement after adding 0.05?wt-% Ti and 0.3?wt-% Zr to the alloy. Fracture surface examinations exhibited a transition from brittle fracture mode in as-cast to ductile fracture in refined and T6 heat-treated specimens.     

Precipitate Behavior in Fe–20Cr–30Ni–2Nb Austenitic Heat-Resistant Steel

In this study,the precipitation behavior of a new austenitic heat-resistant steel(Fe–20Cr–30Ni–2Nb,in at%)was investigated.The effects of alloying addition of boron(B) and lanthanum(La) on the microstructure of the austenitic steel were scrutinized using SEM,EPMA,TEM,and XRD.The results showed that the addition of B enhanced the precipitation of bar-type Laves phase.A small precipitate with high La concentration was observed at the grain boundary in the alloy without aging;similar precipitates without La also presented in region adjacent to the La single phase.This result indicates that La can exist independently and does not contribute to the formation of new compounds.However,in both Band La-modified alloy,B appeared in the precipitate free zone.In the alloy containing both B and La,only Fe2 Nb Lavesphase precipitates,as indicated by the XRD result.     

钛夹杂物细化管线钢热影响区组织研究现状

阐明了钢中夹杂物（氧化物冶金技术）对焊接热影响区组织的影响,综述了钢中各种含钛夹杂物对晶内铁素体的形核机制的研究概况,包括钛脱氧、Ti- Mg复合脱氧、Ti- Nb- N复合脱氧、Ti- Al复合脱氧及Ti- Mn- Si复合脱氧等几项措施,探讨了在这些措施下,如何对铁素体的形成提供最佳条件。最后,对钛夹杂物细化管线钢焊缝组织研究的发展做出了展望。     

一种新的DNA模体发现聚类求精算法

模体发现问题是分析基因转录调控关系的一个重要方面．提出了一种新的基于熵的聚类求精算法--ECRmotif,用于DNA序列中的模体发现问题．ECRmotif使用灵活的概率模型从背景序列中鉴别模体．它首先使用一个基于熵的聚类过程将数据集划分为若干子集,并对各候选子集压缩其实例的搜索空间,求精得到模体．通过模拟数据和真实数据的实验,表明ECRmotif算法可以有效地提高运行速度和效率,并准确地找出模体．     

Rapid Hydrogen Transportation Along Grain Boundary in Nickel

The permeability and diffusivity of hydrogen in directionally solidified polycrystalline and single crystal nickel foils were measured by gas permeation method.The results showed that both hydrogen diffusivity and permeability were higher in directionally solidified nickel specimen than those in single crystal one at the temperature ranging from 300 to480 °C,and confirmed the existence of short-circuit diffusion along the grain boundaries(GBs) in the directionally solidified nickel.The results suggested that the rapid diffusion along GBs was more obviously characterized in terms of higher permeability rather than higher diffusivity.The contribution of grain boundary to hydrogen transportation was represented by the differences of diffusivity(and permeability) in single crystal nickel and directionally solidified nickel.By modifying the Fick's first diffusion law and counting the grain boundary density,the hydrogen diffusivity and permeability of rapid diffusion along GBs were calculated.The results suggested both the diffusivity and permeability fit the Arrhenius relationship well at different temperature.