压力铸造(Al_(63)Cu_(25)Fe_(12))_p/AZ91复合材料的研究

在CO2/SF6气氛保护下,采用压铸的方法将小于74μm的Al63Cu25Fe12准晶粉末注入到熔融的AZ91镁合金中,在720℃和一定的压力下保压30min,制备了新型的体积分数为10%的(Al63Cu25Fe12)p/AZ91镁基复合材料。采用扫描电镜(SEM)和能谱分析仪(EDAX)分析了复合材料中准晶颗粒与基体金属之间的反应,并且研究了复合材料不同于基体材料的热处理工艺过程和性能的关系。结果表明,在复合过程中,准晶I相出现了分解,分解出的自由Cu向基体扩散并与基体中的Al发生了反应,生成的金属间化合物分布在准晶颗粒的周围,同时Mg向颗粒中浸渗,填充到颗粒的孔隙中;复合材料具有不同于基体镁合金的固溶时效特征,需要更长的时间才能达到时效峰值;复合材料经过热挤压和热处理后的力学性能显著提高,抗拉强度从AZ91铸态材料的189.54MPa提高到359.38MPa,但塑性有所降低。     

Al-Cu-Fe准晶及其晶体类似相与纯Mg的界面反应

分析了按照Al63Cu25Fe12配比常规凝固制备的AlCuFe准晶材料的相组成, 研究了块状AlCuFe准晶材料与熔融纯镁的界面反应,发现在界面处存在物质交换作用. 镁与AlCuFe准晶材料有良好的浸润性, 这归因于准晶材料中孔隙的存在、亚稳相的分解和表面氧化层与Mg的反应.     

粉末热压法制备的(Al_(63)Cu_(25)Fe_(12))_p/7055复合材料研究

采用球磨的方式制备了-200目粒度的Al_(63)Cu_(25)Fe_(12)粉末,然后利用粉末热压的形式,制备了不同配比的(Al_(63)Cu_(25)Fe_(12))_p/7055复合材料。结果表明:Al_(63)Cu_(25)Fe_(12)准晶颗粒均匀分散在复合材料中,而且准晶与基体金属的结合良好。比例为8%Al_(63)Cu_(25)Fe_(12)颗粒的复合材料抗拉强度最高达380MPa。     

铸态Al63Cu25Fe12准晶的制备

采用常规铸造方法制备了Al63Cu25Fe12准晶,研究了热处理条件对其相变的影响。结果表明:铸态Al63Cu25Fe12准晶材料组织为多相结构,以准晶I相为主,还包括先析出的λ-(Al-Cu)13Fe4、β-Al-Fe(Cu)、τ-Al-Cu(Fe)等。Al63Cu25Fe12合金铸锭经过750℃×4 h淬火处理之后得到趋于单一的准晶I相。     

热处理工艺对Al65Cu20Cr15准晶颗粒/Al基复合材料组织与性能的影响

采用热压方法制备了Al65Cu20Cr15准晶颗粒／Al基复合材料，对热处理前后复合材料的显微组织及硬度进行分析，结果表明：在500％高温退火过程中，准晶颗粒中的Cu和Cr原子向纯铝基体中扩散，基体中的Al原子向颗粒中扩散，从而使二十面体准晶相颗粒转变为十次准晶及其类似相，硬度有所降低；基体中，退火过程高温过饱和的Cu以Al2Cu的形式析出，而淬火过程高温过饱和的Cu来不及充分析出，产生固溶强化效应，使淬火后基体的硬度显著增加。     

粉末冶金制备SiC_P/2009Al复合材料的相组成和元素分布

采用粉末冶金法制备SiCp/2009AI复合材料热压锭,并对热压锭进行了热挤压,分析了热压态和挤压态复合材料的相组成和元素分布.结果表明:热压锭存在轻微的元素偏析,下部Cu和Mg含量略高于上部.热压态复合材料组成相主要为Al,SiC,Al2Cu和Mg2Si,另外还含有少量的Al7Cu2Fe和Mg的氧化物.经固溶处理后,Al₂Cu和Mg₂Si溶解,Cu在基体中均匀分布,但Mg仍偏聚于原始铝颗粒边界和SiC团聚处.挤压变形不改变复合材料的相组成,但使SiC分布更均匀并破碎了铝颗粒表面的氧化膜.挤压态复合材料经固溶处理后,Cu和Mg均在基体中均实现了均匀分布.     

热处理过程中SiCp/2024Al基复合材料的微观组织演变

采用真空热压烧结工艺在580℃下制备了35%(体积分数)SiCp/2024铝基复合材料,利用扫描电镜(SEM)、透射电镜(TEM)、能谱(EDS)、高分辨透射电镜(HRTEM)对复合材料热处理过程中微观组织进行了表征,研究了热压烧结后复合材料的析出相的微观结构以及析出相在热处理过程的演变规律。结果表明,热压烧结后复合材料中存在许多粗大析出相颗粒,包括Al4Cu9,Al2Cu,Al18Mg3Mn2,Al5Cu6Mg2和Al7Cu2Fe。随着固溶温度的提高,粗大析出相颗粒逐渐回溶到Al基体中,当固溶温度达到510℃时,粗大析出相颗粒几乎全部回溶到基体中,但还存在少量的难溶相。复合材料经510℃固溶2 h+190℃时效9 h后,除了少量的难溶相,许多圆盘状纳米析出相Al2Cu和棒针状纳米析出相Al2Cu Mg弥散分布于基体中且与基体的界面为错配度较小的半共格界面,圆盘状纳米析出相的直径为50~200 nm,棒针状纳米析出相长度为100~150 nm。     

铝基激光涂覆Al-Cu-Fe准晶涂层

采用激光熔覆方法将Al、Cu、Fe的混合粉末在铝基材料上制备复合准晶涂层.研究了重熔对相形成的影响及其硬度变化.涂覆层中的胞状组织由基体开始生长.准晶Ⅰ相可以在各个区域结合铝化合物形成.同样,准晶Ⅰ相还可以由液相和Al13Fe4发生包晶反应形成,也可以从液相中直接形核而成.很明显,在不同的过冷度下,激光热处理过程中液相转变是先于初生相形核的.涂覆层的最外层,伴随着十字星状Al13Fe4形成.就相转变而言,涂覆层的重熔导致了组织的变化,长条状的Al13Fe4就是在重熔时形成的.激光涂覆层和重熔层的硬度均可以达到600左右（HV0.025）.     

准晶增强铝基复合材料的微观组织及热膨胀行为

以铝粉(+200目)为基体、准晶颗粒(粒度≤30μm)为增强相,采用粉末冶金法制备了准晶颗粒增强铝基复合材料.采用光学显微镜、扫描电镜、能谱分析仪分析了该复合材料的微观组织及界面结合特征,并用TMA设备研究了复合材料在25～500℃的热膨胀行为.XRD和SEM分析结果均证明准晶具有良好的结构和热稳定性.准晶颗粒与Al基体之间存在成分均匀且界面厚度均匀的过渡层(厚度＜1μm),且准晶颗粒在Al基体内均匀分布.TMA结果表明:颗粒尺寸对复合材料的热膨胀系数影响最为显著,当颗粒尺寸为10～30μm时,其线膨胀系数达到最小值16.25×10-6/℃;复合材料的热膨胀系数随着颗粒含量的增加而减小.     

铝基激光涂覆Al-Cu-Fe准晶涂层

采用激光熔覆方法将Al、Cu、Fe的混合粉末在铝基材料上制备复合准晶涂层。研究了重熔对相形成的影响及其硬度变化。涂覆层中的胞状组织由基体开始生长。准晶I相可以在各个区域结合铝化合物形成。同样,准晶I相还可以由液相和Al13Fe4发生包晶反应形成,也可以从液相中直接形核而成。很明显,在不同的过冷度下,激光热处理过程中液相转变是先于初生相形核的。涂覆层的最外层,伴随着十字星状Al13Fe4形成。就相转变而言,涂覆层的重熔导致了组织的变化,长条状的Al13Fe4就是在重熔时形成的。激光涂覆层和重熔层的硬度均可以达到600左右(HV0.025)。     

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.