Experimental investigation on the cooling helium circulation of the internal purifier pilot plant

The internal purifier is utilized to remove impurities from impure helium, keep the helium free of any gaseous contaminants. However, there is few report on the performance improvement of the internal purifier. In this paper, we present a novel circuit of the experimental platform with GM cryocooler providing a separated cooling helium circulation as the refrigeration power supply for investigating the performance the internal purifier. Namely, that circuit is easily constructed by extracting a small stream of helium from the high-pressure side of the GM cryocooler serving as the cooling helium circulation. The experiment is then carried out to test the mass flow and the temperature of the cooling helium circulation. The impact of the modification on the cold head is also estimated. It is finally demonstrated that the circuit is sufficient to guarantee the cooling supply of the whole experimental system, which means that the modification is suitable and efficient.     

Oxidation behaviour of zirconium alloys and their precipitates – A mechanistic study

The precipitate oxidation behaviour of binary zirconium alloys containing 1 wt.% Fe, Ni, Cr or 0.6 wt.% Nb was characterised in TEM on FIB prepared transverse sections of the oxide and reported in previous studies [1], [2]. In the present study the following alloys: Zr1%Cu, Zr0.5%Cu0.5%Mo and pure Zr are analysed to add to the available information. In all cases, the observed precipitate oxidation behaviour in the oxide close to the metal-oxide interface could be described either with delayed oxidation with respect to the matrix or simultaneous oxidation as the surrounding zirconium matrix. Attempt was made to explain these observations, with different parameters such as precipitate size and structure, composition and thermodynamic properties. It was concluded that the thermodynamics with the new approach presented could explain most precisely their behaviour, considering the precipitate stoichiometry and the free energy of oxidation of the constituting elements.The surface topography of the oxidised materials, as well as the microstructure of the oxide presenting microcracks have been examined. A systematic presence of microcracks above the precipitates exhibiting delayed oxidation has been found; the height of these crack calculated using the Pilling–Bedworth ratios of different phases present, can explain their origin. The protrusions at the surface in the case of materials containing large precipitates can be unambiguously correlated to the presence of these latter, and the height can be correlated to the Pilling–Bedworth ratios of the phases present as well as the diffusion of the alloying elements to the surface and their subsequent oxidation. This latter behaviour was much more considerable in the case of Fe and Cu with Fe showing systematically diffusion to the outer surface.     

Research on Preheating of Titanium Alloy Powder in Electron Beam Melting Technology

研究了电子束熔化快速成形技术中的钛合金粉末预热工艺,并对粉末预热后的颗粒联接方式进行了分析.结果表明,当Ti6A14V粉末由电子束连续扫描快速预热升温至600℃以上,粉末颗粒中高比表面积的细小颗粒,由于高能量密度电子束作用将全部或部分熔化而充当粉末颗粒联接团聚的粘结剂,使得预热区域的粉末颗粒聚团结块.该粉末团聚体不仅能有效抵挡高速电子束流的冲击而使熔化成形的表面粉末不飞溅,而且也能避免成形表面粉末颗粒熔化时的球化效应.以Ti6Al4V粉末为原料并充分预热每层的成形粉末,制备了层间熔合良好并且力学性能优异的Ti6Al4V柱状试样.     

Zr-0.80Sn-0.4Nb-0.4Fe-0.10Cr-xCu合金在400 ℃过热蒸气中的耐腐蚀性能

采用静态高压釜腐蚀试验研究了Zr-0.80Sn-0.4Nb-0.4Fe-0.10Cr-xCu(x=0.05~0.5,质量分数,%)合金在400℃,10.3MPa过热蒸气中的耐腐蚀性能,用TEM和SEM分别观察了合金的显微组织和氧化膜的断口形貌。结果表明:当Cu含量不超过0.2%时,合金中析出的第二相主要是尺寸较小的Zr(Fe,Cr,Nb)2型和少量尺寸相对较大的含Cu的Zr3Fe型;当Cu含量超过0.2%时,合金中析出了Zr2Cu型第二相,随着Cu含量的增加,Zr2Cu型第二相尺寸增大,数量增多;在添加0.05%Cu的合金中就有含Cu第二相的析出,说明Zr-0.80Sn-0.4Nb-0.4Fe-0.10Cr-xCu合金-Zr基体中固溶的Cu含量很低。当Cu含量不超过0.35%时,合金的的耐腐蚀性能基本没有差别;但是当Cu含量达到0.5%时,由于合金中析出了尺寸较大、数量较多的Zr2Cu型第二相,致使合金的耐腐蚀性能变差。     

掌握运用先进技术 促进钼业可持续发展

掌握与运用先进技术,诸如辉钼矿浮选高效捕收剂、矿物综合利用技术、氧压氧化钼精矿方法、溶剂萃取法生产钼酸铵、高效催化剂生产技术和低钾、铀、钍高纯钼粉生产技术等,以提升与拓展钼产业链条,促进钼业可持续发展。     

TiO2纳米管阵列晶化处理研究进展

综述了近年来TiO2纳米管阵列、非金属掺杂以及金属掺杂TiO2纳米管阵列晶化的最新研究成果,指出TiO2纳米管膜晶化的核心工艺参数为晶化处理温度、升降温速率、热处理气氛等,并对今后的研究提出了展望.     

电感耦合等离子体原子发射光谱法测定TaNb6合金中铌和10种杂质元素

使用氢氟酸、盐酸、硝酸混合酸溶解TaNb6合金样品,选择Nb 309.418 nm、Fe 259.940 nm、Cr 267.716 nm、Ni 221.647 nm、Mn 257.610 nm、Ti 336.121 nm、Al 167.076 nm、Cu 224.700 nm、Sn 189.989 nm、Pb 261.418 nm和Zr 339.19 8 nm为分析线,在仪器最佳工作条件下,采用电感耦合等离子体原子发射光谱法(ICP-AES)测定TaNb6合金中铌、铁、铬、镍、锰、钛、铝、铜、锡、铅和锆,从而建立了TaNb6合金中铌及10种杂质元素的测定方法。采用基体匹配法绘制校准曲线可消除基体效应的影响。各待测元素校准曲线线性回归方程的相关系数均大于0.999 5;方法中各元素的检出限为0.000 1～0.02 μg/mL。按照实验方法测定TaNb6样品中铌、铁、铬、镍、锰、钛、铝、铜、锡、铅、锆,结果的相对标准偏差(RSD,n=7)为0.021%～0.25%,与国家标准GB/T 15076—2008(钽铌合金成分测试的规定方法)测定结果相吻合。     

Internal stress superplasticity in anisotropic polycrystalline materials

A theoretical model of internal stress superplasticity is developed in a single-phase polycrystalline material with an anisotropic thermal expansion. Quasi-steady-state creep equation during a thermal cycle is derived quantitatively based on continuum micromechanics. The model assumes that the generated mismatch strain is accommodated simultaneously by the plastic flow of the material. The linear creep deformation, which corresponds to internal stress superplasticity, is obtained at low applied stress region, and the creep rate depends on the crystallographic texture of the material. The validity of the model is experimentally verified using polycrystalline zinc which is a typical metal having large anisotropy in thermal expansion. The calculated strain rates using the texture information and the isothermal creep equation agree quantitatively well with the experimental results. The apparent activation energy of thermal cycling creep reveals 1/n (n: stress exponent of isothermal creep) of that of isothermal creep, which is one of the characteristics of internal stress superplasticity. Except for the factors attributable to the material geometry, the thermal cycling creep equation in the polycrystalline material is identical to that in a metal matrix composite.     

Microstructure,Texture, and Hardness Evolution of Cold-Rolled High-Purity Ti Sheet During Annealing at 350 °C to 550 °C

Metallurgical and Materials Transactions A - The microstructural, textural, and hardness evolution of a cold-rolled high-purity Ti sheet (50 pct reduction in thickness) during isochronal annealing...