7xxx系铝合金“双峰”时效工艺的普适性研究

采用洛氏硬度计、电子拉伸实验机、冲击实验机等手段对多种7xxx系铝合金超长时间时效行为和性能进行了研究.结果表明,这些合金的硬度、强度等性能都具有时效"双峰"特征.两个"时效峰"的硬度和强度相差不多,但"第二时效峰"时合金具有高强、高韧、低应力腐蚀敏感性等优异性能.     

合金成分与热处理对6xxx系铝合金力学性能的影响

研究合金成分（Mg,Si,Cu）和热处理（自然时效和预时效）对6xxx系铝合金力学性能的影响。结果表明：合金成分与热处理不仅影响材料的成形性能,而且影响材料的烘烤硬化性能;提高合金中Si含量或Si／Mg比或添加0．3％Cu,可显著提高材料的韧性和成形性能,而预时效将减低材料的韧性和成形性能。对所研究合金的强度、韧性、加工硬化、应变敏感性、成形极限和烘烤硬化性进行了比较和总结。     

铝合金板温成形和热成形技术应用研究

为解决强度高的铝合金板材冷成形时塑性差、容易开裂及回弹量大等问题,铝合金温成形和热成形技术受到关注.对铝合金板温成形和热成形的特点进行了论述,对于5xxx系铝合金,温、热成形可有效提高合金成形性能,实现对形状复杂零件的成形,但强度不会增加;而对于6xxx系或7 x x x系铝合金,采用固溶处理-成形-冷模淬火(HFQ)...     

铝合金的晶间腐蚀与剥蚀

综述了近几十年来国内外在2xxx系和7xxx系铝合金及Al-Li合金的晶间腐蚀和剥蚀等研究方面的主要进展.总结了合金中晶界沉淀相的成分、分布及其与晶格的击穿电位差异等对晶间腐蚀的影响规律,探讨了热处理时效状态对合金耐蚀性和局部腐蚀动力学的影响机制.同时探讨了合金的晶格形态、腐蚀产物楔入作用等因素对合金剥蚀过程的影响规律,并对合金的晶间腐蚀和剥蚀研究中所采用的一些快速可靠的无损监检测方法,如电化学阻抗谱（EIS）,进行了评价.     

7xxx铝合金的应力腐蚀行为综述（英文）

应力腐蚀是材料在应力和腐蚀环境双重作用下使材料力学性能下降的行为。对于八种系列铝合金,2xxx、5xxx、7xxx铝合金对于应力腐蚀敏感。由于其优越的力学性能,7xxx铝合金广泛应用于航空、军事和结构工业。在这些7xxx铝合金中,应力腐蚀严重影响其力学性能,使其在服役过程中发生灾难性的失效。因此,研究该合金的应力腐蚀行为具有重要意义。本文综述了合金成分对合金在不同热处理条件下的显微组织演变,还综述了改善7xxx合金应力腐蚀性能的形变热处理和表面改性方法。此外,还综述了应力、预应变、合金成分和腐蚀环境对应力腐蚀行为的影响。还综述了焊缝、7xxx金属基复合材料和激光表面处理合金的应力腐蚀行为。     

7xxx系铝合金热处理的进展

7xxx系合金是基于Al-Zn-Mg（-Cu）系的可热处理的锻铝合金，广泛应用于高性能航空结构和运输部件。除了受成分、铸造和形变热处理影响外，材料性能的平衡明显受到其所经历的热处理方式的影响。描述了均匀化、固溶处理、淬火、时效对7xxx系高强合金组织和性能的影响。总结了在Monash大学进行的有关厚板产品的生产工艺，包括从均匀化到最终的时效处理，以及通过控制微观组织特征，比如弥散体、粗粒子、精细析出相、晶粒结构和晶界特征，来实现组织与性能的平衡。重点陈述了相关方法，如通过高温热处理溶解不需要的粗粒子、基于连续冷却析出行为的淬火敏感性变化、通过实验与建模来研究时效包括一步时效、两步时效、三步时效。对每种情况下的组织与性能都进行研究。     

7475铝合金的逆转变和再时效之敏感性

Al—Zn—Mg—Cu 系(7000系)高强度铝合金广泛应用于飞行器结构。经常选用这类合金的原因是由于它们可因沉淀硬化而获得高强度。一般来说,最好是将这类合金时效到接近于其最高强度,这种合金状态用 T6来表示。但是在这种状态下,合金的应力腐蚀断裂抗力较低。此合金的应力腐蚀断裂抗力可以通过过时效到其 T73状态而提高,但与此同时却使其强度大约降低10～15%。在1974年发现了一种称为逆转变和再时效(Retrogression and reaging)(RRA)的热处     

应力应变状态对蠕变时效7050合金硬化行为及拉伸性能的影响

通过三点弯曲加载方式对7050铝合金板材进行蠕变时效处理,研究了蠕变时效过程中的应力和应变状态对合金的时效硬化行为、拉伸性能及其各向异性的影响。结果表明,蠕变时效降低了合金的峰值时效硬度,应力状态对蠕变时效合金的时效硬化行为有一定的影响,压应力延长了合金达到峰值时效的时间,且压应力状态时效合金的峰值硬度比拉应力状态时效合金的峰值硬度稍低;在弹塑性应变状态下进行蠕变时效的合金具有较高的起始硬度,但在蠕变时效过程中,合金的硬化速率明显低于在弹性状态下进行蠕变时效的合金,当达到峰值时效时,弹塑性应变状态和弹性应变状态蠕变时效合金的硬度没有明显差别;与无应力时效合金相比,蠕变时效合金的强度和塑性都有所下降,弹塑性状态蠕变时效合金的强度和塑性比弹性状态蠕变时效合金的强度和塑性下降幅度稍大,但总体上,应变状态对蠕变时效合金拉伸性能的影响较小;蠕变时效7050合金的拉伸性能仍具有明显的各向异性,但在弹塑性状态下进行蠕变时效可以减小合金垂直于变形方向上的拉伸强度的下降。     

7075高强度铝合金多级时效处理及微观组织分析

以7075系高强度铝合金挤压材为研究对象,对比合金的力学性能(强度、韧性、断裂韧性)、微观组织,并重点研究了其固溶处理后的双级时效热处理工艺.结果表明,7075挤压材采用适宜的双级时效热处理工艺后具有良好的综合性能,其抗剥落腐蚀性能优于T6单级人工时效状态的性能,在保证强度满足设计要求的前提下,提高了7075型材的抗应力腐蚀性能.     

7XXX系列铝合金时效处理工艺的研究

7XXX系列铝合金具有密度小、比强度高以及良好的加工性能,是航空航天领域的主要结构材料之一。本文综述了7XXX系列铝合金时效工艺的研究,并介绍了时效工艺对7XXX系列铝合金组织与性能的影响。7XXX系列铝合金时效特点是:峰值时效(T6)的7XXX系列合金具有高强度,但对应力腐蚀非常敏感;双级时效可以改善合金的应力腐蚀敏感性,但大幅度降低了合金的强度;三级时效(RRA)兼顾了T6和双级时效的优点,能够满足各领域对其性能的要求。     

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.