Ti—Nb微合金钢焊接粗晶热影响区组织及韧性

利用碳萃取复型技术研究了Ti—Nb微合金钢及其模拟粗晶区(CGHAZ)中的第二相粒子，并利用OM、TEM及系列冲击试验对Ti—Nb微合金钢焊接粗晶区的组织及韧性进行了研究。研究结果表明，Ti—Nb微合金钢中含有大量的、尺寸细小的TixNb1-x(CyN1-y)粒子，粒子中Nb的相对含量在0．25—0．82之间，形状接近球形。这些粒子具有很高的稳定性，在焊接过程中这些粒子能有效地阻止奥氏体晶粒长大、抑制粗大贝氏体的形成、促进针状铁素体析出及M-A组元的分解，从而显著善低合金高强钢焊接粗晶热影响区的韧性，t8/5越大，这种改善作用越明显。     

焊接热循环对X-60管线钢中第二相粒子的影响

利用萃取复型技术。对Ti-V-Nb微合金钢母材及模拟焊接粗晶热影响区中第二相粒子进行了研究。结果表明，母材中的粒子为含有Ti、Nb、V的碳氮化合物复合粒子，其尺寸均在100nm以下；粒子的形状不规则，不同粒子具有不同的成分。焊接热循环后，焊接粗晶区中仍保留了较多的粒子，但粒子尺寸显著增大，粒子的形状由母材中的不规则状变为方形，粒子的含Ti显著提高。     

含Ti微合金钢中的第二相粒子对焊接粗晶热影响区组织及韧性的影响

利用碳萃取复型技术研究了含Ti微合金钢及其模拟粗晶区 (CGHAZ)中的第二相粒子 ,并利用OM(光镜 )、TEM(透射电镜 )及系列冲击试验对含Ti微合金钢及一种成分相近的不含Ti低合金高强钢焊接粗晶区的组织及韧性进行了研究。研究结果表明 ,含Ti微合金钢中含有大量的、尺寸细小的TiN粒子 ,这些粒子非常稳定 ,在焊接热循环过程中能有效地阻止奥氏体晶粒长大 ,抑制粗大贝氏体的形成 ,促进针状铁素体析出及M -A组元的分解 ,从而显著改善低合金高强钢焊接粗晶热影响区的韧性 ,t8/5(80 0～5 0 0℃冷却时间 )越大 ,这种改善作用越明显     

高Ti,Nb析出强化高强钢接头强度及焊接热影响区软化行为分析

采用混合气体（80％Ar＋20％CO2）保护焊对高Ti,Nb析出强化高强钢进行了焊接强度试验研究．结果表明,随着焊接热输入增大,接头强度有降低趋势．焊接热影响区较母材硬度降低,存在软化行为．粗晶区晶粒长大及10nm以下（Ti,Nb,Mo）（C,N）第二相粒子的溶解造成强化效果降低．未溶的（Ti,Nb,Mo）（C,N）第二相粒子固定了C,Mo元素,降低过冷奥氏体的稳定性,不能得到硬度较高的板条状马氏体或贝氏体,而形成硬度较低的粒状贝氏体．第二相强化效果的降低不能通过组织强化有效弥补,从而造成粗晶区软化．在细晶区热循环作用下,10nm以下第二相粒子粗化,使得偏离其临界强化尺寸,析出强化效果降低,造成细晶区软化．     

Zr对高强度钢热影响区第二相粒子及韧性影响

研究了0.012 4%锆对低合金高强度钢焊接热影响区粗晶区第二相粒子和冲击韧性的影响.结果表明,模拟20 kJ/cm焊接线能量下无锆钢焊接热影响区粗晶区中第二相粒子为Al-Ti复合氧化物和（Ti,Nb） N析出物.而含锆钢则是Zr-Al-Ti复合氧化物及（Al,Ti,Nb） N和（Ti,Nb） N析出物.同时,定量数据分析表明含锆钢中氧化物和氮化物粒子密度更高且尺寸更加细小.这些高密度的细小的第二相粒子在焊接过程中能有效钉扎晶界移动,抑制奥氏体晶粒粗化,在焊接热影响区粗晶区中得到尺寸相对细小均匀的原奥氏体晶粒,使得含锆钢焊接热影响区粗晶区呈现韧性断裂和极好的低温冲击韧性.     

合金钢焊接热影响粗晶区的显微组织和低温韧性

对船体用合金钢进行Ti脱氧和Al脱氧处理,研究焊接线能量对合金钢焊接热影响粗晶区显微组织和低温韧性的影响。结果表明,随着焊接线能量的增加,Ti脱氧处理钢和Al脱氧处理钢的低温韧性逐渐减小。焊接线能量通过改变第二相粒子的数量和尺寸影响奥氏体晶粒的长大过程。     

低碳微合金Ti-Nb可焊钢中的N及其第二相粒子

研究了系列低碳微合金Ti-Nb可焊钢中的N含量对模拟焊接热影响区(HAZ)高温奥氏体晶粒尺寸和冲击韧度的影响及其第二相粒子的作用.对试样进行了大热输入焊接热模拟,测定了高温奥氏体晶粒尺寸和焊后试样中的冲击韧度值,并用透射电子显微镜萃取复型法观察了典型试样中第二相粒子(Ti,Nb)N的形态及分布特征.结果表明,钢中Ti、N含量及第二相粒子的尺寸和数目与高温奥氏体晶粒尺寸及冲击韧度值具有很好的对应关系;钢中的N由于生成了细小弥散分布的第二相粒子(Ti,Nb)N而细化了高温奥氏体晶粒,改善了焊后韧性.低碳微合金Ti-Nb钢中适宜的含氮量有一个范围.     

Ti、N含量对焊接粗晶区晶粒尺寸及韧性的影响

利用焊接热模拟方法及析出相形貌观察,研究了不同Ti、N含量的高Nb管线钢焊接粗晶区的奥氏体晶粒尺寸及其分布规律、析出相对奥氏体晶粒尺寸及冲击韧性的影响.结果表明:焊接热影响区(HAZ)析出相粒子为富Ti的TixNb1-x(CyN1-y)复合粒子,其尺寸大多数在100 nm以下.分析认为高铌钢中Ti含量应控制在0.010%～0.015%间(Ti/N值在2～3间),该范围内奥氏体晶粒尺寸能被有效钉扎,冲击韧性值显著提高.     

船板钢第二相粒子在大热输入焊接热循环中的变化

利用萃取复型和焊接热模拟技术,研究了不同焊接热循环条件下,大热输入焊接用EH40船板钢粗晶热影响区(CGHAZ)中第二相粒子尺寸、数量和分布等情况及其对该区域奥氏体晶粒长大的影响。结果表明,随着冷却时间(t_(8/5))的延长,CGHAZ中粒子的平均尺寸增大,粒子数量减少。但是,即使是在t_(8/5)=400 s时,CGHAZ中仍存在大量细小弥散的第二相粒子,有效阻止了奥氏体晶粒的长大,说明该船板钢具有优异的焊接性能。     

微Ti钢焊接热循环过程中的第二相粒子

采用“Ｓｐｅｅｄ”法电解萃取复型技术,用透射电子显微镜,研究了分别含有Ｔｉ－Ｎ和Ｔｉ－Ｎｂ－Ｎ的两种微合金钢焊接热模拟后,第二相粒子的溶解析出行为及对焊接热循环的响应。系统测定了不同热模拟工艺下第二相粒子的尺寸、数目及分布特征;分析了热模拟工艺参数（峰值温度Ｔｐ,保温时间ｔｐ,冷却时间ｔｍａｘ／８）对析出颗粒尺寸分布特征的影响,探讨了钢中第二相颗粒的长大、溶解行为对高温奥氏体晶粒度的影响以及微量Ｎｂ与Ｔｉ复合添加的作用。结果表明,微量Ｔｉ－Ｎｂ复合合金化对高温奥氏体晶粒的细化经仅用微Ｔｉ合金化的钢更强烈,钢中微细第二相粒子对细化高温奥氏体晶粒具有主要作用。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.