Alnico合金添加量对Nd-Fe-B薄带磁体的微结构和磁性能的影响

在Nd_2Fe_(14)B合金中添加具有调幅分解能力的Alnico合金,采用熔体快淬法在40m/s的快淬速度下制备出名义成分为Nd_2Fe_(14)B+x%Alnico(x=0,3,5)的薄带磁体,探究多元复合添加Alnico合金组成元素对薄带磁体的微结构和磁性能的影响。试验结果表明:在薄带磁体中形成了由硬磁性相Nd2Fe14B、软磁性相Fe7Co3、弱磁性或非磁性相Al_3Ni和Al_(13)Co_4以及部分非晶相组成的合金体系,在x=3时获得了最佳的综合磁性能:Hc=665kA/m,Br=0.58T,Br/Bs=0.60。     

用机械合金化法制备Sm—Fe合金及其晶化与氮化过程探讨

研究了用机械合金化方法制备的Sm_2Fe_(17)合金的晶化与氮化过程。结果表明:机械合金化的Sm-Fe合金是Sm-Fe非晶相与晶态α-Fe的混合物,其成分是不均匀的,Fe在非晶颗粒外层含量较少,晶化过程包含Fe原子的长程扩散和固相反应,在适当的晶化条件下,晶化后全部转化为Sm_2Fe_(17)相。晶化过程中,可能出现六方结构的Th_2Ni_(17)型Sm_2Fe_(17)亚稳相。氮化过程由孕育期、Sm_2Fe_(17)相与其氮化物相共存、最终全部转化为氮化物相三阶段组成;在氮化过程中有十分细小的少量α-Fe析出。     

Co含量对熔体快淬Fe_(55-x)Co_xPt_(15)B_(30)合金的组织结构与磁性能的影响

研究了Co含量对熔体快淬Fe_(55-x)Co_xPt_(15)B_(30)(x=0~45,原子分数,%)合金热处理前后的组织结构和磁性能的影响。结果表明,添加Co可提高Fe_(55-x)Co_xPt_(15)B_(30)合金的非晶形成能力,使x=15~45的快淬合金形成非晶态。经适当热处理后,合金中形成了由有序面心四方结构的永磁(Fe,Co)-Pt(L1_0)相和软磁(Fe,Co)2B相及(Fe,Co)B相组成的纳米复相组织,显示出永磁性;添加Co的合金组织得到明显细化,x=15~45合金平均晶粒尺寸均约为18 nm;其中x=15合金具有最佳的永磁性能,磁能积达到94.4 k J/m3。合金的矫顽力随Co含量的增加而增大,在x=30时达到最大值413.7 k A/m后,随Co含量的进一步增加而减小;这是由于不同Co含量使L1_0相的c/a值发生变化而导致其磁晶各向异性变化的结果。     

快淬SmFe合金的微观结构及相组成

采用SEM、XRD、EDX、AFM等方法分析了快淬Sm-Fe合金的微观结构和相组成。研究表明：Sm-Fe合金铸锭由Sm2Fe17相、富Sm相和大量的α-Fe相组成，经过一定的均匀化热处理后，获得了几乎单一的Sm2Fe17相合金；快淬速度为10m／s时，获得的Sm-Fe合金由Th2zn17，菱形对称结构的Sm2Fe17相及少量的α-Fe组成，合金晶粒尺寸约为100nm，且分布不均匀：当快淬速度为20m／s时，合金仍由Sm2Fe17相和α-Fe相组成，但与10m／s的合金相比，α-Fe相明显增多，同时稳定相Sm2Fe17向亚稳定相Sm10Fe90转变；当快淬速度大于30m／s时，合金完全为ThCu7型六角晶结构的Sm10Fe90相，平均晶粒尺寸在40～50nm，分布均匀。     

Fe替代Ni对铸态及快淬态La0.7Mg0.3Co0.45Ni2.55-xFex (x = 0-0.4)电极合金循环稳定性的影响

用铸造及快淬工艺制备了La0.7Mg0.3Co0.45Ni2.55-xFex(x=0,0.2,0.3,0.4)电极合金,研究了Fe替代Ni对合金循环稳定性及微观结构的影响。结果表明,Fe替代Ni显著地改善合金的循环稳定性,且Fe替代Ni对快淬态合金的循环稳定性具有更加显著的作用。试验合金具有多相结构,包括2个主相(La,Mg)Ni3和LaNi5以及1个残余相LaNi2。Fe替代Ni促进快淬态合金形成类非晶结构,随Fe含量的增加,快淬态合金的晶粒显著细化,合金的晶格常数及晶胞体积显著增大。     

高性能Sm_2Fe_(17)N_3永磁粉末的还原扩散工艺研究

研究了还原扩散法(R/D)制备Sm_2Fe_(17)合金及通过气-固相反应法生成Sm_2Fe_(17)N_3磁粉的工艺过程。工艺过程引入乙二氨四乙酸的氨水溶液以优化水洗工艺,借助XRD和SEM分析测试手段对Sm-Fe合金扩散、渗氮过程和机理分别进行理论分析和实验研究,通过VSM分析了Sm_2Fe_(17)N_3磁粉的磁滞回线。获得了最佳磁性能的磁粉:Ms=133.43A·m~2/kg、Mr=122.46A·m~2/kg、Hci=795.2kA/m、(BH)max=180.64kJ/m~3。     

添加Sm对快淬Nd_2Fe_(14)B薄带磁性能的影响

研究了快淬Nd_(12-x)Sm_xFe_(84)B_6(x=0~12)薄带的磁性能。结果表明:快淬速度为30 m/s,矫顽力和磁化强度都随Sm含量的增加而减少。剩磁比随Sm含量的增加呈现先降后升再降的趋势。由于Sm_2Fe_(14)B的磁晶各向异性低于Nd_2Fe_(14)B,随Sm替代量的增加,Nd_(12-x)Sm_xFe_(84)B_6合金的磁晶各向异性逐渐降低,导致矫顽力逐渐减少。     

Nd_2Fe_(14)B/α-Fe双相纳米永磁合金的X射线无标定量相分析

通过确定Nd_2Fe_(14)B中各原子的坐标,进而采用计算K值直接对比法,建立了对Nd_2Fe_(14)B/α—Fe双相永磁合金的相含量分析计算程序。对X射线衍射积分强度进行织构修正后,即可由程序计算出不同淬速下制备的Nd_2Fe_(14)B/α-Fe双相永磁合金中各相的体积含量。     

Preparation of Sm_2Fe_(17) alloy by reduction-diffusion process

Sm_2Fe_(17) alloy is the intermediate material for the preparation of Sm_2Fe_(17) Nx(x ≈ 3); thus, the synthesis of pure Sm_2Fe_(17) mother alloy is the key to obtaining highperformance Sm_2Fe_(17) Nx. Reduction-diffusion(R-D) is a cost-effective method. In this study, the R-D process of synthesizing Sm_2Fe_(17) was analyzed by scanning electron microscopy(SEM), energy-dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), and X-ray fluorescence(XRF). Furthermore, the influences of the tightness of compacted reactants, the compensation amount of Sm_2 O_3,and the particle size of Fe on the formation of Sm_2Fe_(17) were discussed from the aspects of the three raw materials.The results show that Sm reduced from Sm_2 O_3 reacts with Fe particles to form intermetallic compound Sm_2Fe_(17) directly in the R-D reaction process of preparing Sm_2Fe_(17);the generation of Sm and its migration to the surface of Fe particles control the reaction rate; a proper tightness of compacted reactants is necessary for ensuring the purity of Sm_2Fe_(17) product; pure Sm_2Fe_(17) can be obtained when the compensation of Sm_2 O_3 is 33 % of the stoichiometry; and the sufficiency of the reaction improves with the decrease in the size of Fe powders under the same reaction condition.     

硼添加对Fe-Ga合金相结构和磁致伸缩的影响

研究了（Fe0．81Ga0．19）100-xBx（x=0-20）合金的相组成和磁致伸缩特性．结果表明：x=1时,铸态合金由A2（bccFe（Ga））相和Fe2B相组成;x=5,10,15,20时,为A2相、L12（α—Fe3Ga）相和Fe2B相组成．800℃保温3h油淬后,当x=1,5时,为修正的DO3（Fe3Ga）相和Fe2B相组成;x=10,15,20时,为修正的D03相、L12相和Fe2B相组成．加入B元素后铸态合金的饱和磁致伸缩系数λs在x=1和10处出现峰值;油淬后随着B含量增加,合金的磁致伸缩系数先增大后减小,其中x=10合金的λs比相应油淬Fe81Ga19合金的λs增加了80％．油淬态合金,随B含量添加,析出Fe2B相,导致Fe-Ga合金基体中修正的D03相的Ga含量相应提高,磁致伸缩提高;随着B含量的进一步增加,合金中出现了过多的Fe2B相和L12相,磁致伸缩下降．     

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.