SCR工艺参数对A2017半固态合金组织的影响

采用自行设计的SCR实验机制备A2017半固态合金，研究了SCR工艺参数对A2017半固态合金组织的影响。实验结果表明，合金液浇注温度和轧辊冷却水流量共同影响辊靴间隙中半固态合金的固相率，降低浇注温度或者增大冷却水流量，辊靴间隙高固相率合金区间增长，晶粒尺寸变小；减小辊靴间隙或者提高轧辊转速提高合金层流剪切强度，利于枝晶破碎；增大出口半固态浆料冷却速率能有效抑制晶粒继续生长，保留其完整的非枝晶半固态组织。合金液浇注温度为760～780℃，辊靴间隙为4～6mm，轧辊冷却水流量200～300ml／s条件下，SCR技术可获得浆料状A2017半固态合金，凝固后坯料为均匀、细小的非枝晶等轴晶组织，晶粒大小在40～50μm之间，SCR技术是一种制备半固态加工坯料的理想方法。     

工艺条件对AZ91镁合金半固态流变轧制组织的影响

利用自行设计的半固态流变轧制装置,成功制备了断面为5 mmx50 mm的AZ91镁合金板材,并研究了工艺条件对制品组织的影响.结果表明:在工作辊线速度一定的条件下,浇注温度在650～730℃变化时,随着浇注温度的降低,固相率增大,浆料受到倾斜板的剪切作用增强,合金组织逐渐细化.当浇注温度一定时,工作辊线速度在0.052～0.087m ·s-1,变化时,随着工作辊线速度增大,轧制时间缩短,组织中固相率减小.当浇注温度和工作辊线速度不变时,在工作辊中通冷却水提高桨料的冷却强度,提高了合金的过冷度及形核率,有效抑制了晶粒的长大,工作辊通水冷却更容易获得组织细小的制品.在本试验条件下,半固态流变轧制AZ91镁合金的最佳工艺条件:工作辊通水冷却,浇注温度为650 ℃,工作辊线速度为0.052m·s-1.     

LY11合金的半固态成形研究

研究了变形温度和应变速率对半固态和供应态LY11合金峰值流动应力、稳态流动应力以及微观组织的影响.由试验结果可知:变形温度对LY11合金的峰值应力影响显著,对稳态应力影响较小.应变速率对峰值应力的影响与变形温度有关.变形温度对微观组织的影响是:随着变形温度的升高,半固态LY11合金的近球状晶粒不断长大,供应态LY11合金的不规则细长晶粒逐渐向近球状转变,这种转变有助于改善材料的流动性能.     

AZ31镁合金型材连续流变挤压成形过程的数值模拟

通过数值模拟,分析AZ31镁合金在连续流变挤压成形过程中的温度场与流场分布规律。结果表明:辊-靴型腔内合金的温度从入口至出口逐渐降低,合金等温线向工作辊偏移;随着浇注温度的降低,辊-靴型腔内半固态区间逐渐增大;为了获得优良的半固态金属浆料,确定浇注温度为710～770℃;合金在辊-靴型腔内层流运动时,越靠近工作辊内表面,合金的运动速度越快;随着挤压模具扩展角的增大,挤压模具出口型材宽度上中心与两侧边部合金的温度差减小;半固态合金进入模具后呈辐射状逐层向前推进填充模具扩展腔,最后再逐渐向模具出口合拢;为了改善模腔内金属流动速度的不均匀性,扩展角以45°为宜。     

SIMA制备半固态LY11合金的工艺研究

研究了应变诱发熔化激活法 (SIMA)制备半固态LY11合金过程中的变形温度、变形速度、等温温度和保温时间等工艺参数对LY11合金组织演变的影响。研究结果表明 ,要获得均匀、细小的非枝晶组织 ,必须合理地匹配SIMA工艺参数     

SCR技术半固态制浆热流偶合场的三维有限元模拟

在ANSYS有限元软件求解平台上对SCR技术半固态制浆过程热流耦合场进行三维模拟,给出了不同工艺参数下的温度场和速度场的分布情况,并将模拟结果与实验结果进行比较.结果表明,在旋转工作辊拽动下,辊靴型腔内合金做层流运动,各流层的速度从工作辊表面到靴表面呈线性递减.合金温度从辊靴入口到出口逐渐下降,在速度场影响下,合金温度场等温线向工作辊面发生偏移,近工作辊面温度偏高.随着合金液浇注温度的升高、辊靴型腔高度的增加或者工作辊转速的提高,出口半固态浆料的温度升高,与实验结果一致.     

SCR技术制备2A11兰固态合金的研究

在介绍单辊剪切／冷却技术制备半固态2A11合金材料原理的基础上，提出了半固态2A11合金球形晶粒组织形成的新观点；被晶破碎与内液体合金形核形成自由晶，自由晶自由运动生长而球化。研究分析表明：烧注温度、冷却强度、轧辊转速与辊靴表面性质影响半固态2A11合金组织。     

高效节能制备半固态合金浆料的新工艺

应用高效节能的工艺制备了半固态合金浆料,该工艺采用了低过热度浇注和弱电磁搅拌。研究了主要工艺参数对半固态合金浆料的影响。结果表明,低过热度浇注和弱电磁搅拌工艺可制备满足流变成形所需的半固态合金浆料,浇注温度和搅拌功率显著影响初生α-Al晶粒的形貌和尺寸。通过对合金熔体的弱电磁搅拌,可适当提高低过热度浇注的温度,实现高效和节能的目的。     

半固态LY11合金的压缩变形

研究了变形温度和应变速率对半固态LY11合金变形行为和微观组织的影响.研究结果表明:在液固温度区间变形时,变形温度、应变速率对半固态LY11合金的流变应力峰值影响显著,对稳态流变应力影响较小.对微观组织的影响是:随着变形温度的升高和应变速率的降低,固相晶粒尺寸增大,但仍保持初始的近球状.在半固态合金的压缩过程中,随着工艺参数的变化,占主导地位的变形机制也随之变化.     

新型倾斜板技术制备半固态铝合金坯料和浆料

采用自行设计的波浪型倾斜板,在斜板冷却条件下制备了组织和触变性能优良的半固态合金坯料。而在斜板加热条件下制备出了组织优良的半固态合金浆料。在采用波浪型的倾斜板制备半固态合金过程中,在熔体爆发形核与枝晶破碎的共同作用下,形成了细小球形的半固态合金组织,浇注温度、冷却强度、斜板倾角和斜板表面材质是影响半固态合金组织的主要因素。得出了本试验条件下制备AlMg3合金半固态坯料的浇注温度范围为660~690℃;制备AlSi6Mg2合金半固态坯料的浇注温度范围为660~680℃;制备AlSi6Mg2半固态合金浆料的合理工艺条件为:斜板预热温度为300℃时,合金浇注温度为680℃。     

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.