La0.8-xRExMg0.2Ni3.2Co0.6储氢合金的结构及电化学性能

通过感应容炼制备了La0.8-xREMg0.2Ni3.2Co0.6(RE=Sm,Dy,0≤x≤0.3)合金.采用X射线衍射分析了该合金的晶体结构,并研究了其电化学性能.结果表明:该合金是由LaNi5主相和LaNi3第二相构成;随着Sm(Dy)取代La量的增加,合金主相单胞体积线性收缩,合金储氢量和放电容量减小,当Sm(Dy)取代量分别为0.1、0.2、0.3时,合金容量由380 mA·h/g分别减小到370(362)、355(334)、329(295)mA·h/g,但高倍率放电能力和循环稳定性得到改善,100次循环后的容量损失率由20%分别降低到18%(17%)、16%(14%)、13%(11%).     

稀土元素对La0.8 Mg0.2 Ni2.8 Co0.6 储氢合金性能的影响

以La0.8Mg0.2Ni2.8Co0.6合金为基材,采用感应熔炼法制得以Ce,Pr,Nd部分替代La的系列储氢合金。3种稀土元素的加入对合金的组织没有本质的影响。与La0.8Mg0.2Ni2.8Co0.6的相组成相似,新合金也是在主相LaNi5中含有LaNi3第二相,且随着Ce,Pr,Nd替换量的增多,LaNi3相所占比例升高。在La0.8-xRExMg0.2Ni2.8Co0.6合金中,当Pr替换至x=0.2时,新合金基本保持La0.8Mg0.2Ni2.8Co0.6的放电容量375mA·h/g;其他添加比例及添加元素都在一定程度上降低了新合金的放电容量。加入Ce和Pr普遍提高放电电位,而Nd对放电电位的影响不大。La0.8Mg0.2Ni2.8Co0.6的容量衰减速率为1.07mA·h/(g·cycle),当Ce,Pr,Nd分别替换至x=0.3,0.6,0.6时,新合金的容量衰减速率依次降低到0.566,0.625,0.453mA·h/(g·cycle),循环稳定性有了很大提高。     

La1-xCaxNi3.2Co0.3Al0.3低钴储氢合金的组织与性能

通过X射线衍射、扫描电镜和能谱分析了新型低钴储氢合金La1-xCaxNi3.2Co0.3Al0.3(0≤x≤0.4)合金的晶体结构、组织形貌及各相化学成分,并研究了该合金的电化学性能.结果表明:当x≤0.1时,合金基本保持LaNi5主相和LaNi3第二相;当0.1＜x≤0.3时,出现的Al(NiCo)3第二相替代了LaNi3第二相.随着Ca含量的增加,合金活化性能变差,当x=0.2时,放电容量达到最高值(为295 mA·h/g),合金经300次充放电后,循环容量保持率为82.5%,且循环寿命得以改善.     

Hydrogen Storage Properties of Co-free La-Mg-Ni-Based Alloys

在Ar气保护下采用磁悬浮感应熔炼方法,制备无CoLa1.8Ti0.2MgNi9-xAlx(x=0,0.1,0.2,0.3,0.4)合金,系统研究Al取代Ni对合金的结构及贮氢性能的影响。所有合金均包含LaMg2Ni9相,当Al含量x≥0.1,La(Ni,Al)5相取代LaNi5相、LaNi3相消失、LaNi2相出现。测试合金的焓变值与LaNi5合金(–30.6kJ/molH2)相近。Al取代Ni不仅提高合金电极的放电容量,而且改善循环稳定性及电化学动力学性能。La1.8Ti0.2MgNi8.7Al0.3合金贮氢性能较好,30℃下有效吸氢质量分数为1.32%;最大放电容量达到340mAh/g;1400mA/g放电电流密度下高倍率放电性能HRD1400高达79.8%;经100次充放电循环放电容量保持率为60%。     

少量Si对无钴AB5型储氢合金性能的影响

采用电弧熔炼制备了La(NiAlMn)5-xSix(0≤x≤0.35)合金.借助XRD,SEM等分析了La(NiAlMn)5-xSix储氢合金的晶体结构和相组成,并研究了合金的电化学性能.结果表明:当x≤0.3时合金由LaNi5单相组成;当x=0.35时合金由主相LaNi5和第二相LaNi3构成.随着Si含量的增加,合金储氢量和放电容量减少.但是循环稳定性得到了改善.经300次充放电循环,合金在x=0.35时的容量损失率为19.4%.这是因为Si的加入使得合金的抗氧化性,耐腐蚀性得到了改善.     

La_(0.7)Mg_(0.3)Ni_(2.8)Co_(0.5-x)Fe_x系列合金的制备及其储氢性能

在制备La-Ni-Co-Fe中间合金的基础上,采用机械合金化方法制备La0.7Mg0.3Ni2.8Co0.5-xFex(x=0,0.1,0.2,0.3,0.4,0.5)系列储氢合金,研究在不同球磨时间下储氢合金的物相、微观形貌和电化学性能及元素置换对其储氢性能的影响。结果表明:La0.7Mg0.3Ni2.8Co0.5合金的主相为LaNi5相,La0.7Mg0.3Ni2.8Co0.5-xFex系列储氢合金球磨40 h和80 h后,主相为LaNi5相和少量LaMg2Ni9相;且随着球磨时间的增加,合金晶粒变细小,La0.7Mg0.3Ni2.8Co0.5合金的最大放电容量呈变大的趋势,从142.4 mA.h/g增加到157.5 mA.h/g,La0.7Mg0.3Ni2.8Co0.2Fe0.3合金的最大放电容量从150.7mA.h/g增加到162.1mA.h/g,合金具有较好的循环稳定性能。     

Lao.7Mgo.3Ni2.8Coo.5-xFex系列合金的制备及其储氢性能

在制备La-Ni-Co-Fe中间合金的基础上,采用机械合金化方法制备La0.7Mg03Ni2.8C005-xFex(x=0,0.1,0.2,0.3,0.4,0.5)系列储氢合金,研究在不同球磨时间下储氢合金的物相、微观形貌和电化学性能及元素置换对其储氢性能的影响.结果表明La0.7Mg0.3Ni2.8Co0.5合金的主相为LaNi5相,La0.7Mg0.3Ni2.8Co0.5-xFex系列储氢合金球磨40h和80h后,主相为LaNi5相和少量LaMg2Ni9相;且随着球磨时间的增加,合金晶粒变细小,La0.7Mg03Ni2.8Co0.5合金的最大放电容量呈变大的趋势,从142.4mA.h/g增加到157.5mA.h/g,La0.7Mg0.3Ni2.8Co0.2Fe0.3合金的最大放电容量从150.7mA·h/g增加到162.1mA·h/g,合金具有较好的循环稳定性能.     

La-Mg-Ni系AB3型贮氢电极合金的相结构与电化学性能

XRDRietveld分析显示,LaxMg3-xNi9(x=1.0-2.3)均由六方PuNi3型结构的主相及少量LaNi5及MgNi2杂相组成,主相的晶胞参数随x的增加而线性增大.合金的氢化物仍保持PuNi3型结构,但其晶胞体积有较大的膨胀.电化学测试表明,随x增加,合金的最大放电容量由88.3(x=1.0)逐渐增大到397.5mA·h/g(x=2.0),然后又降低到230mA·h/g(x=2.3).对放电容量超过348mA·h/g的合金(x=1.7-2.2),在放电电流i=400-1200mA/g的条件下,合金的高倍率放电性能(HRD)均随x增加而有不同程度的降低.HRD的缓慢降低主要与合金电极进行电荷迁移反应时的电催化活性的逐渐降低有关,而在x＞2.0时,HRD的快速降低与氢在合金中的扩散速率明显降低有关,上述合金经100次循环后合金的容量保持率为55.7%-62.9%,容量衰退较快与循环过程中La和Mg的氧化腐蚀以及合金较大的吸氢体积膨胀率有关.     

无钴LaNi4.1Al0.3Mn0.4Si0.2Fex (x=0~0.4)储氢合金性能

采用电弧熔炼制备LaNi4.1Al0.3Mn0.4Si0.2Fex(x=0~0.4)储氢合金,借助XRD、SEM等分析LaNi4.1Al0.3Mn0.4Si0.2Fex合金的晶体结构和相组成,并研究合金的电化学性能。结果表明:合金主要由LaNi5单相组成,当x≥0.1时,在LaNi5主相上分布着些许灰色的第二相。随着LaNi4.1Al0.3Mn0.4Si0.2Fex(x=0~0.4)合金中Fe的加入量增加,合金最大放电容量由295.4mAh/g(x=0)降低到278.2mAh/g(x=0.4),活化次数也由10次增加到18次。同时合金200次循环后的容量保持率却由66.85%(x=0)提高到93.33%(x=0.4)。     

Al对La—Mg-Ni系贮氢合金电极电化学性能的影响

采用固相扩散法制备La0.7Mg0.3Ni3.5-xAlx(x=0,0.1,0.3,0.7,1.0)和La0.7Mg0.3Ni2.8Co0.7-xAlx(x=0,0.1,0.2,0.3,0.4)贮氧合金,采用X射线衍射、能谱分析及循环伏安等方法分析含金的相结构和电极电化学性能,研究元素Al替代对合金电化学性能的影响.结果表明:合金由LaNi5、La2Ni7和LaNi3三相组成,随着Al替代量的增加,La2Ni7相晶胞逐渐膨胀,LaNi5相大量减少,LaNi3相增加,La2Ni7相有利于合金电化学性能的提高,然而过高的Al含量会对合金的放电性能带来不利影响.La0.7Mg0.3Ni3.4Al0.1和La0.7Mg0.3Ni2.8Co0.6Al0.1合金电极的最大放电容量分别为354.5 mA·h/g和373.1 mA·h/g.循环伏安测试显示较明显的氧化峰和还原峰,且峰电位差较小,反映合金电极较好的吸放氢反应可逆性.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.