添加Nb元素对耐热不锈钢组织和硬度的影响

采用高频感应加热设备熔配合Nb量为0～2.0％的耐热不锈钢样品.研究了Nb含量对耐热不锈钢基体组织、碳化物形态及合金硬度的影响规律.结果表明:随着Nb含量的增大,奥氏体枝晶形态由粗大枝晶→等轴晶→细小枝晶→粗大枝晶转变;碳化物由粗大长条状→细小短棒状/点块状→连续网状形态转变;相应的,合金硬度则呈现出先增大后减小的趋势,硬度值在125～175 HB之间.     

高频电磁场对灰铸铁凝固组织的影响

研究了在高频电磁场作用下凝固的灰铸铁试样不同位置的石墨形态、共晶团组织及其硬度。结果表明:施加高频电磁场后灰铸铁石墨形态发生明显变化,由试样底部向上,石墨由长直粗大的片状变为分布在枝晶间的细小点状或片状,试样顶部呈均匀细小弯曲的片状;共晶团尺寸减小,试样硬度明显提高。高频电磁场的洛伦兹力作用和焦耳热效应对灰铸铁熔体的流动形态和温度分布产生影响,增加了结晶核心数量,减小温度梯度,使凝固组织更加均匀细小。     

微合金化铸铁同质焊条焊接工艺

应用微合金化铸铁同质焊条,采用小电流打底、大电流连续焊工艺,研究了预热温度与焊缝组织及性能之间的相关性.结果表明,微合金化铸铁焊条石墨化能力强,焊缝白口倾向小;小电流打底、大电流连续焊工艺可有效地减小熔深,在很大程度上抑制了熔合区白口的产生.微合金化铸铁焊条可实现常温焊接.预热温度小于200℃即可获得组织和性能与母材一致的同质焊缝.随着焊件预热温度的升高,焊缝中的石墨形态由细小的点状逐渐向菊花状、片状过渡,铁素体含量增多,焊缝硬度减小.焊件预热至200℃所获得的焊缝组织由珠光体、铁素体和细片状石墨及菊花状石墨组成,熔合区则由珠光体、少量碎块状铁素体及过冷石墨片组成,接头力学性能良好.     

国家标准《灰铸铁金相检验》解读

1 标准的历史概况 灰铸铁是指金相组织中石墨呈片状的铸铁.灰铸铁具有优良的铸造工艺性,断屑性好,适合高速切削;炉料要求相对宽松,熔化温度较低,生产简便、成本低;减震性、减摩性好,抗压强度高等特点,适合铸造薄壁、复杂铸件;故在铸造材料中的用量最大. 我国最早的灰铸铁金相检验标准是JB 2264-1978《灰铸铁金相》,该标准将石墨形状按特征分为A型石墨:片状石墨均匀分布;B型石墨:片状与点状石墨聚集成菊花状;C型石墨:部分带尖角块状、粗大片状初生石墨及小片状石墨;D型石墨:点状和片状枝晶间石墨呈无向分布;E型石墨:短小片状枝晶间石墨呈有方向分布;F型石墨:星状(或蜘蛛状)与短片状石墨混合均匀分布.石墨长度按ASTM标准分为八级.     

Ni元素和变质剂对亚共晶铝铁合金组织的影响

采用水冷快速冷却铜模制备含铁0.30％～1.55％(质量分数)的亚共晶铝铁合金,用光学显微镜、TEM和EDX分析方法研究了Fe、Ni元素和变质剂对合金组织的影响.结果表明:随着Fe、Ni含量的增加,合金晶界处共晶化合物增多,二次枝晶增多并相互连接成网状,晶界处颗粒状A19FeNi相呈层状分布.当Fe、Ni含量分别增加到1.55％、1.5％时,组织呈层状分布,并含有粗大针状和长针片状初生相.变质剂A1-Ti-B和稀土元素Ce均可显著细化粗大的含铁初生相,消除枝晶组织,但A1-Ti-B对α-Al相晶粒细化效果不明显,而稀土Ce能显著细化α-Al相与共晶组织.     

高镍球铁同质电焊条焊缝组织形成规律

针对铸铁在焊接过程中焊缝易产生白口、裂纹和淬硬组织等技术难题.采用自制高镍球铁同质电焊条,探索了高镍球铁同质焊缝组织形成规律及其与接头力学性能的相关性.结果表明,焊缝组织由分枝细小的柱状奥氏体枝晶+球状石墨+少量晶间碳化物组成.焊接电流的增大使焊缝中柱状晶变得粗壮,石墨球化率升高,晶间碳化物数量增多.当焊接电流一定时,随着预热温度的增大,石墨形态变差,碳化物数量增多,接头抗拉强度减小而硬度增大.采用大电流不预热焊接工艺可以获得综合性能优良的铸铁同质焊缝.     

热处理条件对V_(55)Ti_(30)Ni_(15)合金显微硬度的影响

研究了热处理条件对V55Ti30Ni15合金显微组织和硬度的影响。结果表明,V55Ti30Ni15合金铸态组织为枝晶结构,并且枝晶之间有网状粗大的多相组织。而对V55Ti30Ni15合金进行热处理会使其硬度下降。     

CoCrFeMnNiCu_x高熵合金的微观组织及力学性能

采用真空电弧炉制备了CoCrFeMnNiCu_x高熵合金,研究了不同Cu含量对该体系高熵合金的微观组织及力学性能的影响。结果表明,高熵合金的微观组织为树枝晶,合金的枝晶富含Co、Cr、Fe,而枝晶间富含Ni、Mn。Cu易偏析于枝晶间,添加Cu并没有使合金晶体结构发生改变,仍为FCC结构。随着Cu含量的增加,合金的抗压强度及显微硬度先增大后减小,但增减幅度很小。当x=0.8时,合金的抗压强度和硬度达到最大值。含Cu的6组元高熵合金的抗压强度及显微硬度明显高于不含Cu的5组元高熵合金。     

激光增材制造高Nb含量GH4169合金微观偏析行为研究

目的减轻不同热处理状态下激光增材制造高Nb含量GH4169合金组织中的微观偏析。方法采用激光增材制造方法对球磨Nb合金化后的合金粉末进行快速成形,获得具有较高Nb含量的GH4169合金试样。通过光学显微镜、扫描电子显微镜及能谱分析、维氏硬度测试方法,对沉积态、固溶态和直接时效态试样进行分析,研究因合金中Nb含量变化引起的微观偏析对沉积态和热处理态合金的枝晶组织和显微硬度的影响。结果随着Nb含量的增加,一方面,由于枝晶间的Nb含量增加,枝晶间(γ+Laves)共晶数量增加,且共晶组织形貌更为连续;沉积态试样的显微硬度由228.4HV增大至534.1HV。另一方面,枝晶干Nb元素含量增加,枝晶干与枝晶间Nb元素含量的差异缩小,Nb元素的偏析比由8.59减小至4.13。后续固溶处理后,枝晶结构逐渐消失,枝晶间Laves相的数量随之减少,枝晶干与枝晶间的微观偏析减轻;固溶态试样硬度值随之减小,减小趋势随固溶温度的升高而逐渐平缓。随着Nb含量的增加,直接时效处理后,各试样显微硬度值在微观区域内的均匀性提高,枝晶干与枝晶间强化相的析出差异减小。结论合适的热处理制度既可以实现合金元素的均匀化,还能减小枝晶干与枝晶间强化相的析出差异,减轻激光增材制造高Nb含量GH4169合金组织中的微观偏析。     

INFLUENCE OF LASERGLAZE ON MICROSTRUCTURE AND WEAR RESISTANCE OF A CAST Ni-BASE SUPERALLOY

本文研究激光快速熔凝对一种新型Ni基铸造超合金显微组织和磨蚀磨损性能的影响。 高Mo,W含量Ni基铸造合金是一种具有低膨胀系数和耐磨耐蚀等特种工程性能的新型材料。因合金中难熔重元素含量较高(33wt-％Mo,17wt-％W),其铸造组织粗大,含有大量高熔点相,并存在严重偏析。 用高能量密度激光快速熔凝表面处理之后,合金组织发生显著改变。全部高熔点相熔化,明显提高固溶度;结晶组织细化,分别为精细枝晶、胞状枝晶、胞状晶和平面凝固组织;熔区内合金元素均匀分布,基本消除偏析。 合金组织变化使其性能进一步改善,熔区硬度明显增加,提高了抗磨擦磨损和在酸性介质中的耐磨蚀性能。     

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.     

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。     

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.     

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.     

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).     

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.