Development in oxide metallurgy for improving the weldability of high -strength low-alloy steel-Combined deoxidizers and microalloying elements

The mechanisms of oxide metallurgy include inducing the formation of intragranular acicular ferrite(IAF)using micron-sized inclusions and restricting the growth of prior austenite grains(PAGs)by nanosized particles during welding.The chaotically oriented IAF and refined PAGs inhibit crack initiation and propagation in the steel,resulting in high impact toughness.This work summarizes the com-bined effect of deoxidizers and alloying elements,with the aim to provide a new perspective for the research and practice related to im-proving the impact toughness of the heat affected zone(HAZ)during the high heat input welding.Ti complex deoxidation with other strong deoxidants,such as Mg,Ca,Zr,and rare earth metals(REMs),can improve the toughness of the heat-affected zone(HAZ)by re-fining PAGs or increasing IAF contents.However,it is difficult to identify the specific phase responsible for IAF nucleation because ef-fective inclusions formed by complex deoxidation are usually multiphase.Increasing alloying elements,such as C,Si,Al,Nb,or Cr,con-tents can impair HAZ toughness.A high C content typically increases the number of coarse carbides and decreases the potency of IAF formation.Si,Cr,or Al addition leads to the formation of undesirable microstructures.Nb reduces the high-temperature stability of the precipitates.Mo,V,and B can enhance HAZ toughness.Mo-containing precipitates present good thermal stability.VN or V(C,N)is ef-fective in promoting IAF nucleation due to its good coherent crystallographic relationship with ferrite.The formation of the B-depleted zone around the inclusion promotes IAF formation.The interactions between alloying elements are complex,and the effect of adding dif-ferent alloying elements remains to be evaluated.In the future,the interactions between various alloying elements and their effects on ox-ide metallurgy,as well as the calculation of the nucleation effects of effective inclusions using first principles calculations will become the focus of oxide metallurgy.

Microstructure and mechanical properties of the welding joint filled with microalloying 5183 aluminum welding wires

In this study, 7A52 aluminum alloy sheets of 4 mm in thickness were welded by tungsten inert gas welding using microalloying welding wires containing traces of Zr and Er. The influence of rare earth elements Zr and Er on the microstructure and mechanical properties of the welded joints was analyzed by optical microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, hardness testing, and tensile mechanical properties testing. Systematic analyses indicate that the addition of trace amounts of Er and Zr leads to the formation of fine Al3Er, Al3Zr, and Al3（Zr,Er） phases that favor significant grain refinement in the weld zone. Besides, the tensile strength and hardness of the welded joints were obviously improved with the addition of Er and Zr, as evidenced by the increase in tensile strength and elongation by 40 MPa and 1.4%, respectively, and by the welding coefficient of 73%.

Effects of Rare-earth and Microalloying Elements on the Microstructure Characteristics of Hypereutectoid Rails

We performed thermal simulation experiments of double-pass deformation of hypereutectoid rails with different microalloying elements at a cooling rate of 1℃/s and deformation of 80%to explore the influence of rare-earth and microalloying elements on the structure of hypereutectoid rails and optimize the composition design of hypereutectoid rails.Scanning electron microscopy,transmission electron microscopy,X-ray diffraction,and other characterization techniques were employed to quantitatively analyzed the effects of different microalloying elements,including rare-earth elements,on pearlite lamellar spacing,cementite characteristics,and dislocation density.It was found that the lamellar spacing was reduced by adding various microalloying elements.Cementite lamellar thickness decreased with the refinement of pearlite lamellar spacing while the cementite content per unit volume increased.Local cementite spheroidization,dispersed in the ferrite matrix in granular form and thus playing the role of dispersion strengthening,was observed upon adding cerium(Ce).The contributions of dislocation density to the alloy strength of four steel sheet samples with and without the addition of nickel,Ce,and Ce–copper(Cu)composite were 26,27,32,and 37 MPa,respectively,indicating that the Ce–Cu composite had the highest dislocation strengthening effect.The Ce–Cu composite has played a meaningful role in the cementite characteristics and dislocation strengthening,which provides a theoretical basis for optimizing the composition design of hypereutectoid rails in actual production conditions.

Role of multi-microalloying by rare earth elements in ductilization of magnesium alloys

The present work investigates the influences of microalloying with rare earths on the mechanical properties of magnesium alloys.The amount of each rare earth element is controlled below 0.4 wt.%in order not to increase the cost of alloy largely.The synergic effects from the multi-microalloying with rare earths on the mechanical properties are explored.The obtained results show that the as-cast magnesium alloys multi-microalloying with rare earths possesses a quite high ductility with a tensile strain up to 25-30%at room temperature.Moreover,these alloys exhibit much better corrosion resistance than AZ31 alloy.The preliminary in situ neutron diffractions on the deformation of these alloys indicate that the multi-microalloying with rare earths seems to be beneficial for the activation of more slip systems.The deformation becomes more homogeneous and the resultant textures after deformation are weakened.

A comparison study of Ce/La and Ca microalloying on the bio-corrosion behaviors of extruded Mg-Zn alloys

The influences of Ca and Ce/La microalloying on the microstructure evolution and bio-corrosion resistances of extruded Mg-Zn alloys have been systematically investigated in the current study.Compared with single Ca or Ce/La addition,the Ca-Ce/La cooperative microalloying results in an outstanding grain refinement,because the fine secondary phase particles effectively hinder the recrystallized grain growth.The coarse Ca2Mg6Zn3 phases promote the formation of Ca3(PO4)2 or hydroxyapatite particles during the immersion process and accelerate the dissolution of the corrosion product film,which destroys its integrity and results in the deterioration of anti-corrosive performance.The Ce/La elements can be dispersed within the conventional Mg7Zn3 phases,which reduce the internal galvanic corrosion between Mg matrix and the secondary phases,leading to an obvious improvement of corrosion resistance.Therefore,the Ca-Ce/La cooperative microalloying achieves a homogenous fine-grained microstructure and improves the protective ability of surface film,which will pave a new avenue for the design of biomedical Mg alloys in the coming future.

Microstructure and Thermoelectric Properties of Bi- and Cu-Substituted Ca_3Co_4O_9 Oxides

Bi- and Cu-substituted Ca3Co4O9 samples were prepared by conventional solid-state reaction method and the effect of element substitution on the microstructures and thermoelectric properties was investigated. Partial substitution of Cu for Co leads to an increase in electrical conductivity and a decrease in Seebeck coefficient due to the rise of hole concentration. The microstructure of Cu-substituted sample is almost unchanged compared with undoped Ca3Co4O9. On the other hand, partial substitution of Bi for Ca gives rise to a significant increase in the grain size, and c-axis-oriented structure can be formed in Ca2.7Bi0.3Co4O9, resulting in an obvious increase in electrical conductivity. Cu and Bi co-substitution further increases the grain growth and the electrical conductivity of Ca2.7Bi0.3Co3.7Cu0.3O9. Thus, Cu and Bi co-substitution samples possess the optimal thermoelectric performance at high temperature and the highest value of power factor can reach 3.1×10^-4 Wm^-1.K^-2 at 1000 K.

Microstructure and Mechanical Properties of Mg-Al-Ca-Nd Alloys Fabricated by Gravity Casting

The aims of this study are to investigate the effects of Nd addition in the Mg-Al-Ca alloys on microstructure and mechanical properties.Microstructure of as-cast Mg-5Al-3Ca alloy containing Nd consists ofα-Mg matrix, eutectic phase and Al-Nd rich intermetallic compound.As Nd addition was increased,α-Mg matrix morphology was changed from dendritic to equiaxed grains and average value of grain size was decreased.Nd addition to Mg-5Al-3Ca based alloys resulted in the formation of Al-Nd rich intermetallic compounds at grain boundary andα-Mg matrix grains.And these Al-Nd rich intermetallic compounds were dispersed homogeneously.In these alloys,two kinds of eutectic phases were observed,i.e.coarse irregular-shape structure at grain boundary and fine needle-shape structure in theα-Mg matrix grain.It is found that the ultimate strength showed the maximum value of 271 MPa at Mg-5Al-3Ca-2Nd alloy and elongation was decreased as the addition of Nd was increased.

Effects of Ca2+concentrations on accumulations of mineral elements in the components of Pteroceltis tatarinowii

The bark of Pteroceltis tatarinowii is a raw material for manufacturing Xuan Paper. The effects of Ca2+ concentrations on the accumulation of mineral elements in the bark, leaf and root of Pteroceltis tatarinowii were studied under controlled condi-tions. The types of Hoagland nutrient solution with three Ca2+ concentrations levels (200, 400 and 600 靏g-1) and a control (without Ca2+) were designed to culture Pteroceltis tatarinowii. After 6 months, contents of seven mineral elements including Ca, K, Mg, Mn, Zn, Cu and Na in the root, leaf and bark were analyzed. The results indicated that Ca accumulations content in the root, leaf and bark had positively relation with Ca2+ concentrations (200, 400, 600 靏g-1), and the order of the Ca content in the three components was root】leaf】bark. Ca content in the root treated with 600 靏g-1 Ca2+ concentrations was 5.5 times as high as that of the control, and about 1.4 times as high as that of the root treated in 200 and 400 靏/g Ca2+ concentrations respectively. On the contrary, K and Mg contents in the root, leaf and bark were negatively related to Ca2+ concentrations, especially in the bark, and their accumulation trend followed the order of leaf】root】bark. K content in the bark treated with 600 靏g-1 Ca2+ con-centrations was 39.3% of that of the control, and was 79.0% and 91.8% of that of the bark treated with 200 靏g-1 and 400靏g-1 Ca2+ concentrations respectively; Mg content in the bark treated with 600 靏g-1 Ca2+ concentrations was 23.4% of that of the control, and was 27.1% and 35.4% of that of the bark treated with 200 and 400 靏g-1 Ca2+ concentrations respectively. Com-pared with the control, the general tendency of Mn, Zn and Cu content decreased with increasing of Ca2+ concentrations and their contents were in the order: root】leaf】bark. Based on the results of this study, the experiment has been useful for providing academic bases in improving the bark quality of Pteroceltis tatarinowii on non-limestone soil.

Kinetic Monte Carlo simulation of microalloying effect in Al-Ag alloys

The kinetic Monte Carlo method, which based on the Multi-States Ising Model, was applied to simulate the effect of microelements on the microstructural evolution of Al-Ag alloys during initial aging stage. The simulation results suggest that the microelements In, Sn and Be have a dramatic depression effect on the Ag clustering because of their strong tendency to co-existed with vacancies. There are no significant effects on the process of Ag clustering in Al-Ag alloys containing Li or Cd, because of little interaction between Li/Cd and Ag/vacancies. Microelements can influence the aging by interacting with vacancies and the atoms of precipitated composition, in which the former seems more important. In this model, “vacancy-locking” and “vacancy clusters” are two important mechanisms in the aging process.

Alpha Decay Half-Lives of New Superheavy Elements through Quasimolecular Shapes

The lifetimes of a decays of the recently produced isotopes of the elements 112, 114, 116 and the element ^294118 and of some decay products have been calculated theoretically within the Wentzel-Kramers-Brillouin approximation. The a decay barriers have been determined in the quasimolecular shape path within a generalized liquid drop model including the proximity effects between nuclei in a neck, the mass and charge asymmetry and the precise nuclear radius. These calculations provide reasonable estimates for the observed a decay lifetimes. The calculated results have been compared with the results of the density-dependent M3Y effective interaction and the experimental data. It is indicated that the theoretical foundation of the generalized liquid drop model is as good as that of the microscopic DDM3Y model, at least in the sense of predicting the T1/2 values as long as one uses a correct a decay energy. The half lives of these new nuclei are well tested from the consistence of the macroscopic, the microscopic and the experimental data.

RE,Ca低合金化AZ31镁合金板材拉胀复合成形性能的研究

研究了稀土、钙元素低合金化对AZ31镁合金板材力学性能、弯曲及拉胀复合成形性能的影响。结果表明:加入0.3%RE,0.3Ca%(质量分数,下同)后,AZ31镁合金板材的晶粒较细、力学性能明显提高,300℃,4h退火后室温抗拉强度为284MPa、延伸率为23.2%;同时,该合金板材具有最好的弯曲及拉胀复合成形性能,随着温度的提高其成形性能进一步提高。

Ca^(2+)对新生大鼠脑缺氧缺血后CREB磷酸化及神经元凋亡的影响

目的 :探讨Ca2 + 对新生大鼠脑缺氧缺血 (HI)后c AMP反应元件结合蛋白 (CREB)磷酸化及神经元凋亡的影响 ,为临床治疗缺氧缺血性脑损伤 (HIBD)提供理论依据 .方法 :7d龄SD鼠 (n =1 2 6 ) ,完全随机分为 3组 :假手术组 4 2只 (仅作颈正中切口 ,游离右颈总动脉不结扎 ) ;缺氧缺血组 4 2只、Ca2 + 拮抗剂加缺氧缺血组 (干预组 ) 4 2只 .后两组用 0号线结扎右颈总动脉 2h ,予以低氧 2h ,制备成缺氧缺血 (HI)脑损伤模型 .干预组动物分别在模型制成前、后腹腔内注射Ca2 + 拮抗剂尼莫地平 .用免疫组化法观察各组HI后不同时间点右侧海马CA1 区P CREB阳性细胞数 ;用TURNEL法观察各组HI后不同时间点右侧海马CA1 区凋亡细胞数 .结果 :HI组右侧海马CA1 区P CREB表达增强 (P <0 .0 1 ) ,4h达高峰后逐渐下降 ;HI组的凋亡细胞数增多 ,4 8h达高峰后逐渐下降 .干预组右侧海马CA1 区P CREB的表达较HI组无明显减少(P >0 .0 5 ) ,但凋亡细胞数较HI组明显减少 (P <0 .0 1 ) .结论 :Ca2 + 对CREB磷酸化无明显影响 ;Ca2 + 参与HI后神经元损伤 ;Ca2 + 拮抗剂可减轻神经元损伤 .

基于1D-CNN的无砟轨道CA砂浆脱空识别

为解决水泥乳化沥青砂浆(CA砂浆)脱空位置识别的难题,提出考虑CA砂浆脱空的无砟轨道模型建模与计算方案。首先,基于CRTS I型板式无砟轨道“梁-板-板”建模理论,使用非线性弹簧模拟CA砂浆脱空病害,输入扣件支点反力作为模型的激励,得到监测点位的垂向加速度数据集。其次,通过对数据集缩放、添加噪声的方式进行数据增强,增强数据集的差异,以增强识别模型的泛化性,获得更加准确的识别结果。最后,建立脱空病害的识别方法,搭建一维卷积神经网络(1D-CNN)进行CA砂浆的脱空位置识别,构建准确率、查准率和查全率等评价指标评估识别结果,使用t-SNE降维算法对结果进行可视化。对比其他3种神经网络的表现,探讨1D-CNN应用于CA砂浆脱空位置识别的优势。研究结果表明:“梁-板-板”模型反映了无砟轨道的力学本征,用于CA砂浆脱空问题的仿真模拟是可行的;通过对数据集信号缩放、添加噪声的方式进行数据增强可提高深度学习模型的性能;从深度学习的角度来看,CA砂浆脱空发生在板中造成的危害较小,应重点关注板端CA砂浆脱空的养护与维修问题;1D-CNN相比其他3种模型运算时间短,在CA砂浆脱空位置识别数据集上优势更大,识别准确率可达95%以上。研究结果为进一步提高无砟轨道结构监测的自动化和智能化水平提供参考。

Behavior of precipitation in bainitic steel during relaxation processing of RPC technique

Thermal simulation test, TEM (Transmission Electron Microscope) and nanobeamEDS (Energy Dispersed x-ray Spectrum) techniques were used to investigate the precipitation behaviorof Nb, Ti, Mo etc. in HSLA (High Strength Low Alloy) steel. The strain induced precipitationoccurred during the isothermal relaxation stage after deformed in the non-recrystallizationtemperature region. After 30% predeformation at 850 and 900℃, there are two kinds of particles,(Ti,Nb)(C,N) and a few Nb(C,N), to precipitate during holding. The content of Nb in particles riseswith the relaxation time increasing. During the final holding stage, some Nb and Ti atoms in thelattice sites of the precipitates would be replaced by Mo atoms, and the Mo content in theprecipitates increases with the relaxation time. The results were compared with the refinementeffect of microstructures caused by relaxation-precipitation controlling transformation (RPC)processing.

A Preliminary Analysis of Trace-Elemental Signatures in Statoliths of Different Spawning Cohorts for Dosidicus gigas off EEZ Waters of Chile

We applied solution-based ICP-MS method to quantify the trace-elemental signatures in statoliths of jumbo flying squid, Dosidius gigas, which were collected from the waters off northern and central Chile during the scientific surveys carried out by Chinese squid jigging vessels in 2007 and 2008. The age and spawning date of the squid were back-calculated based on daily increments in statoliths. Eight elemental ratios(Sr/Ca, Ba/Ca, Mg/Ca, Mn/Ca, Na/Ca, Fe/Ca, Cu/Ca and Zn/Ca) were analyzed. It was found that Sr is the second most abundant element next to Ca, followed by Na, Fe, Mg, Zn, Cu, Ba and Mn. There was no significant relationship between element/Ca and sea surface temperature(SST) and sea surface salinity(SSS), although weak negative or positive tendency was found. MANOVA analysis showed that multivariate elemental signatures did not differ among the cohorts spawned in spring, autumn and winter, and no significant difference was found between the northern and central sampling locations. Classification results showed that all individuals of each spawned cohorts were correctly classified. This study demonstrates that the elemental signatures in D. gigas statoliths are potentially a useful tool to improve our understanding of its population structure and habitat environment.

GLYX-13 pretreatment ameliorates long-term isoflurane exposure-induced cognitive impairment in mice

Accumulating evidence indicates that inhalation anesthetics induce or increase the risk of cognitive impairment. GLYX-13（rapastinel） acts on the glycine site of N-methyl-D-aspartate receptors（NMDARs） and has been shown to enhance hippocampus-dependent learning and memory function. However, the mechanisms by which GLYX-13 affects learning and memory function are still unclear. In this study, we investigated these mechanisms in a mouse model of long-term anesthesia exposure. Mice were intravenously administered 1 mg/kg GLYX-13 at 2 hours before isoflurane exposure（1.5% for 6 hours）. Cognitive function was assessed using the contextual fear conditioning test and the novel object recognition test. The mRNA expression and phosphorylated protein levels of NMDAR pathway components, N-methyl-D-aspartate receptor subunit 2B（NR2B）-Ca2+/calmodulin dependent protein kinase II（CaMKII）-cyclic adenosine monophosphate response element binding protein（CREB）, in the hippocampus were evaluated by quantitative RT-PCR and western blot assay. Pretreatment with GLYX-13 ameliorated isoflurane exposure-induced cognitive impairment and restored NR2B, CaMKII and CREB mRNA and phosphorylated protein levels. Intracerebroventricular injection of KN93, a selective CaMKII inhibitor, significantly diminished the effect of GLYX-13 on cognitive function and NR2B, CaMKII and CREB levels in the hippocampus. Taken together, our findings suggest that GLYX-13 pretreatment alleviates isoflurane-induced cognitive dysfunction by protecting against perturbation of the NR2B/CaMKII/CREB signaling pathway in the hippocampus. Therefore, GLYX-13 may have therapeutic potential for the treatment of anesthesia-induced cognitive dysfunction. This study was approved by the Experimental Animal Ethics Committee of Drum Tower Hospital affiliated to the Medical College of Nanjing University, China（approval No. 20171102） on November 20, 2017.

ALLOYING BEHAVIOUR OF Ca IN STEEL 58CrV

Effect of Ca on hardenability and CCT diagram of steel 58CrV has been investigated by means of end-quenching and thermal expansion.An addition of 0.006 wt-%Ca to the steel may improve the hardenability,reduce the critical cooling rate of transformation of pearlite or bainite under continuous cooling and increase the M_s.AES analysis showed that Ca segre- gates markedly along austenitie grain boundaries,and accelecrates the segregation of C,Cr and Si.It is believed that besides towards deoxidizing and desulphurizing as well as improving sulphide morphology,a trace of Ca in steel 58CrV behaves towards microalloying.

苹果sMdCAX11基因的功能分析与鉴定

【目的】深入分析苹果sMdCAX11(去掉NRR区域的MdCAX11)基因功能。【方法】分别利用蜜脆苹果果实和拟南芥材料,采用过表达sMdCAX11的试验方法,观察果实、叶片等各组织的表型,并测定不同组织的矿质元素含量,同时对苹果MdCAX11基因启动子区域进行预测分析以及启动子转录活性分析。【结果】瞬时过表达sMdCAX11的苹果果肉颜色变褐,并出现皱缩;同时过表达sMdCAX11的苹果果肉和拟南芥叶片的总Ca含量明显下降,且元素比值(K+Mg)/Ca明显升高。【结论】sMdCAX11基因过表达可导致植株组织的元素分配不均,不同元素间的比例失衡。

Ⅴ型CRISPR-Cas系统相关移动遗传元件的研究进展

移动遗传元件是指一段可以发生转座的DNA。CRISPR-Cas是细菌中存在的适应性免疫系统,其进化起源与部分移动遗传元件存在密切联系。总结了V型CRISPR-Cas系统与相关移动遗传元件中不同蛋白质在功能与作用机制方面的异同,分析二者之间在进化上的联系,整理其在基因组编辑等方面的应用,并对其未来发展进行展望。

Y元素对铸态 Mg-Al-Ca-Mn合金组织与耐腐蚀性能的影响

采用金相显微镜、扫描电镜、XRD分析、腐蚀试验和电化学测试等研究了Mg-4Al-3Ca-0.7Mn-xY(x=0、0.8、1.5)铸态合金的微观组织与耐腐蚀性能。结果表明:未添加Y的Mg-4Al-3Ca-0.7Mn合金组织由α-Mg、Al2Ca相、Mg2Ca相组成。添加0.8wt%Y后,合金组织中晶粒得到明显细化,析出相变得细小,Al2Ca相、Mg2Ca相数量减少,并有Al2Y相生成。Y含量增加到1.5wt%时,合金晶粒细化效果不明显,大量Al2Y相聚集在晶界处呈网状分布。添加适量的Y可提高Mg-4Al-3Ca-0.7Mn-xY合金的耐腐蚀性,Y添加量为0.8wt%时,该合金的耐腐蚀性最佳。