保温时间对ZL102合金熔液质量的影响

研究了实际生产中，保温时间对ZL102铝液质量的彤响，探讨了保温时间与变质效果和针孔度之间的关系．结果表明：Sr变质达到最佳变质效果大约需要60min；随着保温时间的延长，Sr以大约每h0.002％(质量分数)的速率烧损，其变质效果可以持续长达6～7h；精炼变质后30～90min，铸件中针孔度最小．铝液质量最好。     

变质工艺对亚共晶Al-Si合金共晶硅细化的影响

研究了工业生产Sr变质亚共晶Al-7%Si合金时,变质剂含量、变质温度、变质时间、浇注温度等工艺参数对合金共晶硅细化及其性能的影响。结果表明,在大规模工业化生产中,上述工艺参数严重影响共晶硅的变质效果。采用Al-10%Sr对亚共晶Al-7%Si合金进行变质,在w(Sr)=0.015%时,保温40min后,共晶团内的Si完全成为圆颗粒状,尺寸为5～10μm,达到最佳变质效果。采用Sr变质亚共晶Al-7%Si合金最佳变质温度为700℃,变质后共晶硅组织分布均匀;浇注温度为640℃时的铸件宏观组织最佳,晶粒度可稳定的达到2级,升高浇注温度,晶粒度提高。精炼后,变质时间为30～60min进行浇注,试样针孔度最小,熔体洁净程度高。     

铝—锶长效变质剂的试验

目前铸造亚共晶、共晶铝硅合金所用的变质剂多以钠盐为主要成分,钠盐具有变质见效快、效果好等优点,但变质效果在合金保温时易衰退,有效期一般在60min以内。为此近十几年来国内外铸造工作者研究了Sr、Ba、Te、RE等长效变质剂,其有效期多在5～10h,但变质后都有一段潜伏期。铝液处理后要在高温停留一段时间才能浇注。Al-Sr中间合金作为变质剂能克服上述二种变质剂的缺点。     

RE和Sr复合精变处理对A356合金冶金质量的影响

考察了RE和Sr复合处理对A356合金的精炼变质效果,以减压凝固试样密度来评定熔体中氢含量水平.试验结果表明RE和Sr的同时加入,充分发挥了两者的优越性,不仅有效改善了Sr变质处理铸件因针孔多而报废的情况,同时也得到了相当于Sr的变质效果.复合处理后合金的力学性能也达到了要求.     

变质剂对ZL101铝合金吸气量及力学性能影响

采用不同变质剂对ZL101铝合金进行变质处理,通过密度当量仪研究铝液在不同时间的气体含量。变质完成后在不同时间取样,研究铝合金气体含量及其对应铸件的力学性能的变化。结果发现,经钠盐变质与除气后铝液气体含量可控制在0.5左右,而且在放置过程中铝液吸气量增幅较小,力学性能降幅较小。采用Sr合金变质铝液气体含量可控制在1左右,但在放置过程中铝液的吸气量持续增加,而力学性能特别是伸长率大幅下降。经铸件剖面发现,Sr变质的铸件中有大量的微小气孔存在。     

RE-Sr复合变质对轮毂用A356合金组织性能的影响

针对汽车轮毂用A356合金在Sr变质处理时熔体的吸气性增大,造成铸件气孔疏松、针孔度不合格等问题,采用主要成分为La和Ce的混合稀土RE与Sr联合对A356合金进行复合变质实验。结果表明,复合变质相比单一Sr变质,熔体中的氢含量显著降低。在一定范围内,RE和Sr具有协同变质作用,当采用0.2%Sr+0.2%RE时,铸件的微观组织、力学性能和导电率达到最优。     

JGJ-1铝合金精炼剂的研制及应用

阐述了JGJ—1铝合金精炼剂的研制及工业生产条件下的应用效果.在正常生产条件下,用该精炼剂除气,试样达到1~2级针孔度;所处理的合金浇注铸件废品率低;该精炼剂发气量大、用量少、对铝液氧气小、不污染环境且不吸潮、成本低.     

锶变质在消失模铝合金铸造生产中的应用

介绍锶(Sr)变质在用于消失模铝合金铸件时铝液精炼工艺的选择,对Sr变质的潜伏期、Sr的加入量及变质衰退期进行了实验验证。通过严格控制原材料,采用惰性气体除气精炼,铝液符合铸件要求;生产中要根据自身的工艺摸索变质潜伏期及衰退期,变质衰退的铝液可以进行补充变质;砂型铸造为了获得良好变质效果,要想办法改善铸件冷却条件。变质效果好坏与凝固条件密切相关,同样的工艺在金属型比砂型铸造效果好很多。     

稀土变质在汽缸盖铸件上的应用研究

稀土变质与三元变质剂相比,ZL104合金显微组织及机械性能稍有逊色,但符合国标和企标要求。铸件经T_6处理后的硬度较高,因而加工性能较好,并利于铸件刚性的提高;稀土变质有效时间长,晶粒粗大和渣孔等废品减少,故铸件合格率提高;稀土变质解决了因三元钠盐变质剂浸蚀坩埚而使其难以用涂料保护,造成铝液严重渗铁的质量问题;稀土有良好的除气作用,减少了铸件的针孔度。这种工艺适合于金属型低压铸造。     

土和锶对4004铝合金二元变质效果的研究

采用正交试验的方法对变质剂(Sr、RE)的加入量、变质温度和保温时间进行了优化,运用极差分析的方法对各因素的显著性进行了分析,确定了最佳工艺参数:Sr加入量为0.03wt％,RE加入量为0.15wt％,变质温度为740℃,保温时间为60 min.其次,通过对比试验的方法,探索了Sr和RE的加入量对合金组织的影响,当Sr和RE的加入量分别为0.03wt％和0.15wt％时,合金的显微组织已经完全变为细小的点状和短棒状a-Al,变质效果最佳.     

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.     

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。     

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.