On the Quaternary System Ti-Fe-Ni-Al

The homogeneity ranges of the Laves phases and phase relations concerning the Laves phases in the quaternary system Ti-Fe-Ni-Al at 900 °C were defined by x-ray powder diffraction (XPD) data and electron probe microanalysis (EPMA). Although at higher temperatures the Laves phase forms a continuous solid solution, two separate homogeneity fields of TiFe₂-based (denoted by λ_Fe) and Ti(TiNiAl)₂-based (denoted by λ_Ni) Laves phases appear at 900 °C. The relative locations of Laves phases, G phase, Heusler phase, and CsCl-type phase as well as the associated tie-tetrahedra were experimentally established in the quaternary for 900 °C and presented in three-dimensional (3D) view. Furthermore, a partial isothermal section TiFe₂-TiAl₂-TiNi₂ was constructed, and a connectivity scheme, derived for equilibria involving Laves phases in the Ti-Fe-Ni-Al quaternary system at 900 °C was derived. As a characteristic feature of the quaternary phase diagram, the solid solubility of fourth elements in both the TiFe₂-based and Ti(NiAl)₂-based Laves phases is limited at 900 °C and is dependent on the ternary Laves phase composition. A maximum solubility of about 8 at.% Ni is reached for composition Ti_33.3Fe_33.3Al_33.4. Structural details have been evaluated from powder x-ray and neutron diffraction data for (i) the Ti-Fe-Ni ternary and the Ti-Fe-Ni-Al quaternary Laves phases (MgZn₂-type, space group: P6₃/mmc) and (ii) the quaternary G phase. Atom site occupation behavior for all phases from the quaternary system corresponds to that of the ternary systems. For the quaternary Laves phase, Ti occupies the 4f site and additional Ti (for compositions higher than 33.3 at.%Ti) preferably enters the 6h site. Aluminum and (Fe,Ni) share the 6h and the 2a sites. The compositional dependence of unit cell dimensions, atomic coordinates, and interatomic distances for the Laves phases from the quaternary system is discussed. For the quaternary cubic G phase, a centrosymmetric as well as a noncentrosymmetric variety was observed depending on the composition: from combined x-ray and neutron powder diffraction measurements Ti_33.33Fe_13.33Ni_10.67Al_42.67 was found to adopt the lower symmetry with space group .     

PNN测井技术及其应用分析

PNN测井是一种利用测量地层中剩余热中子数量随时间变化关系,从中提取地层的宏观俘获截面,计算储层的剩余油饱和度的方法;其采集方式区别于其它脉冲中子测井,也具备独特的数据处理技术。文章介绍了PNN测井原理、解释方法,并结合实例认为：地层的宏观俘获截面是表征地层中子特性的参数,与地层岩性、裸眼井的伽马曲线有很好的对应关系;PNN测井资料解释须参考生产井史、邻井注水动态资料,才能得出准确的结论。     

B_4C/6061Al中子吸收材料FSW接头的纳米压痕和拉伸性能研究

采用粉末冶金的方法制备了30vol%B_4C/6061Al中子吸收材料板材。通过搅拌摩擦焊(FSW)的方法对4 mm厚30vo1%B_4C/6061A1中子吸收材料板材进行对接焊接,获得了表面成形良好的焊缝。采用纳米压痕法对FSW焊接接头的焊核(WZ)、热力影响区(TMAZ)、热影响区(HAZ)和母材(BM)4个区域中的微区力学性能进行研究,对焊接接头的拉伸性能进行了测试。运用扫描电镜对压痕的微观形貌和拉伸断口进行表征。结果表明:在同一区域中,随着距颗粒/基体界面距离d(d11μm)的增加,微区的硬度和弹性模量总体呈现降低趋势。在微区数值均值化后,不同区域的硬度和弹性模量由高到低为WZ、TMAZ、BM和HAZ,压入功恢复率在WZ、TMAZ、HAZ和BM依次为28.10%、25.14%、31.76%和29.30%。在焊接接头不同区域出现性能差别的原因是由于在FSW过程中不同区域的塑性变形程度和热循环作用不同导致的,FSW接头强度可达母材的85.7%,断裂部位在HAZ区。     

In situ neutron diffraction measurement of strain relaxation in welds during heat treatment

Neutron diffraction (ND) is commonly used to investigate the stress redistribution before and after post-weld heat treatment (PWHT) in welded structures. However, there is a lack of information on the evaluations of strains during PWHT. The present work employed in situ ND to measure the relaxation of residual strains during conventional PWHT in multi-pass high-strength low-alloy steel welds. It was found that strain relaxation occurs principally during the heating stage of the heat treatment. The findings have important economic bearings and can be used to characterise comparable material combinations and optimise the PWHT process for high-strength low-alloy weld joints. This unique information also provides a valuable benchmark for the finite element modelling of this complex process.     

Ni /Ti 多层膜界面状态优化分析

目的减小Ni/Ti多层膜表面粗糙度,提高Ni/Ti多层膜对中子束的反射率。方法采用离子束辅助沉积设备沉积Ni/Ti周期性多层膜,通过不同抛光时间和不同离子能量轰击对多层膜界面进行清洗抛光;采用反应溅射法,在镀Ti层时使用氢气和氩气混合气为工作气体,将H原子掺入Ti层以改变晶粒结构而影响多层膜界面状态。结果随着辅助离子源功率的增加,Ni/Ti多层膜的表面粗糙度增加;在合适的离子能量下,随着抛光时间的不断增加,Ni/Ti多层膜的表面粗糙度逐渐减小。Ti层中掺H的Ni/Ti多层膜比未掺H的多层膜表面粗糙度小,界面更加清晰。结论低能量的离子轰击条件下,适当的抛光时间能对多层膜实现较好的抛光效果。Ti层中掺入H原子,抑制了Ni原子与Ti原子的扩散,减小了Ti膜层晶粒大小,从而抑制了表面粗糙度的增加。     

一种超高强度低合金钢的拉伸微屈服行为的原位中子衍射研究

研究了一种超高强度低合金钢与环境裂纹敏感性（EAC）有关的拉伸微屈服行为。宏观屈服强度为1120MPa,拉伸应力近700MPa开始微屈服的超高强度低合金钢,其化学成分（质量分数,％）为0．22C．0．25Si。0．70Mn．3．40（Cr＋Ni＋Mo）-0．13（V＋Nb＋Ti）。用这种钢制作的深水系泊链环经1273K淬火和873K回火,原位中子衍射测量结果表明,对其光滑圆柱试样施加拉力,至应力500MPa,良好地符合线弹性应变;至700MPa时,（200）晶面族晶粒优先出现非线弹性应变;至800MPa,（110）晶面族晶粒也呈非线弹性应变。随着拉力的进一步增大,（200）晶面族晶粒的非线性弹性应变量逐步增加,而（211）晶面族晶粒仍停留在线弹性应变阶段。     

Grain-size effects in the quasi-static fracture resistance of a thermally embrittled RPV steel (quenched and tempered microstructures)

The elastic-plastic fracture toughness and crack extension behavior under the quasi-static loading regimen of several thermally embrittled conditions of a nuclear reactor pressure vessel (RPV) steel were assessed on the basis of microstructural parameters. It was discovered that the bainite packet size is the fracture properties controlling parameter of single-phase quenched and tempered microstructures. Results were found in close agreement to those obtained in a parallel study with dual-phase annealed microstructures derived from the same low alloy steel. Similarly, it was concluded that a Hall-Petch type relationship correlates J-fracture mechanics criteria to the grain size.     

金属/氧化物界面形成机理原位研究

金属/氧化物界面是控制反应机理和宏观性质的关键区域.原位表征手段可以实时、连续、动态地对金属/氧化物界面形成过程进行研究,其观察和分析结果对理解界面形成过程及其应用有重大学术意义和工程价值.本文综述国内外原位表征金属/氧化物界面的研究工作,主要关注原位透射电子显微镜、原位同步辐射技术、原位中子技术等先进表征分析金属/氧...     

注塑机液压系统的改进设计

对某型注塑机液压系统进行改进设计,将该型注塑机顶模机构的液压中子并联起来。对改进后的注塑机液压系统进行AMESim仿真实验和改进实验,均验证了改进后的注塑机可以缩短注塑成型周期,并可实现二级调速。此改进方法不增加其他液压阀,方法简单且成本低廉,可以提高企业的生产效益。     

Development of MRI-Detectable Boron-Containing Gold Nanoparticle-Encapsulated Biodegradable Polymeric Matrix for Boron Neutron Capture Therapy (BNCT)

This study aimed to develop a novel magnetic resonance imaging (MRI)-detectable boron (B)-containing nanoassemblies and evaluate their potential for boron neutron capture therapy (BNCT). Starting from the citrate-coated gold nanoparticles (AuNPs) (23.9 ± 10.2 nm), the diameter of poly (D, L-lactide-co-glycolide) AuNPs (PLGA-AuNPs) increased approximately 110 nm after the encapsulation of the PLGA polymer. Among various B drugs, the self-produced B cages had the highest loading efficiency. The average diameter of gadolinium (Gd)- and B-loaded NPs (PLGA-Gd/B-AuNPs) was 160.6 ± 50.6 nm with a B encapsulation efficiency of 28.7 ± 2.3%. In vitro MR images showed that the signal intensity of PLGA-Gd/B-AuNPs in T1-weighted images was proportional to its Gd concentration, and there exists a significantly positive relationship between Gd and B concentrations (R² = 0.74, p < 0.005). The hyperintensity of either 250 ± 50 mm³ (larger) or 100 ± 50 mm³ (smaller) N87 xenograft was clearly visualized at 1 h after intravenous injection of PLGA-Gd/B-AuNPs. However, PLGA-Gd/B-AuNPs stayed at the periphery of the larger xenograft while located near the center of the smaller one. The tumor-to-muscle ratios of B content, determined by inductively coupled plasma mass spectrometry, in smaller- and larger-sized tumors were 4.17 ± 1.42 and 1.99 ± 0.55, respectively. In summary, we successfully developed theranostic B- and Gd-containing AuNPs for BNCT in this study.