温度及溶质浓度对Mullite短纤维增强的Al—Cu复合材料及其基体合金时效行为的影响

用挤压铸造方法制备Mullite／Al—Cu复合材料及其基体合金。用硬度测试(HB)、差示扫描量热仪(DSC)和透射电镜(TEM)等手段，研究了温度和溶质原子浓度对复合材料及其基体合金时效行为的影响。结果表明：复合材料和基体合金具有相似的时效硬化曲线及相同的时效析出序列，随时效温度的升高，峰值硬度降低、析出过程加快；溶质浓度升高，峰值硬度升高、析出过程同样得到加快；纤维除了能明显提高Al—Cu合金的时效硬度外，还能加速其时效析出过程，但对GP区的形成具有明显的抑制作用，而对θ相的析出影响不大。     

连续冷却对Al-4%Cu合金时效组织和性能的影响

采用扫描电镜、透射电镜观察、选区电子衍射、电阻率测试、硬度测试和Monte Carlo模拟等方法,研究连续冷却对Al-4%Cu合金(质量分数)时效组织和性能的影响。结果表明,实验合金的连续冷却脱溶产物主要包括θ相、θ′相和θ″相,不同冷却条件形成的析出相组态会导致合金的硬度曲线、电阻率曲线不随冷却速率的降低而单调降低。冷却析出的θ″相作为时效强化相的前驱体能够加速时效强化相析出,导致合金的时效硬化曲线峰值时间提前,但是极慢的冷却条件消耗了大量的溶质原子,导致时效驱动力下降。Monte Carlo模拟表明,连续冷却脱溶导致的残余溶质质量分数降低会减慢Cu原子团簇的形成速率,当残余溶质质量分数低于2%时,模拟时效1800s合金中仍然不会出现明显的团簇,降低了时效强化效率。     

Al-Mg-Si合金时效早期显微组织演变及其对强化的影响

采用显微硬度测试、HRTEM和原子探针层析技术(APT)等测试手段分析了核元件燃料包壳备选材料LT24铝合金在180℃人工时效早期显微硬度、组织变化及析出序列中析出物的Mg与Si原子比(r).结果表明,在180℃时效初期,合金的硬度显著增加,析出高数量密度的溶质原子团簇和球状Guinier-Preston(GP)区;时效4 h后达到硬度峰值,析出物以高数量密度的针状β″相为主;进一步时效,合金处于一硬度平台,析出物仍以β″相为主.随时效时间的延长,析出相逐渐长大,r逐渐增加,β″相中r在1.23~1.35之间,β″相对合金的强化起最重要作用.在早期时效过程中合金析出物的析出序列为过饱和固溶体→溶质原子团簇→溶质原子团簇+GP区→溶质原子团簇+GP区+β″相.     

喷射沉积过共晶AlSiCuMg合金的时效行为和力学性能

利用扫描电镜(SEM+EBSD)、透射电镜(TEM)、硬度测试以及室温拉伸实验研究了喷射沉积过共晶AlSiCuMg合金的时效组织演变规律及力学性能。结果表明：随时效时间的延长，喷射沉积AlSiCuMg合金的硬度先增加后降低；随着时效温度的升高，合金硬度达到峰值所需时间分别为24 h (170℃)、2 h(185℃)和0.5 h (200℃)。合金经185℃时效0.5 h后，在位错处可观察到非均匀析出的细小针状θ″相。在(185℃, 2 h)峰时效状态下，析出相包含细针状θ″相和点状Q′相，同时存在粗针状θ′相。峰时效硬度约为91HRB，比挤压态提高了近72%。合金经185℃时效28 h后，θ′相体积分数明显增加。合金经185℃时效48 h后，析出相演变为粗大的板条状θ相和方块状Q相；过剩Si相开始析出，同时在与入射轴垂直的晶面上观察到包围Si相的粗大盘片状富Cu相。合金经185℃时效56 h后，θ相和Q相演变为粗大椭球状。合金的硬度下降至约80HRB。喷射沉积AlSiCuMg合金的时效析出惯序为：过饱和固溶体→GP区→θ″+Q′→θ′+Q′→θ+Si+Q′→θ+Si+Q。合金的峰值时效...     

Ag，Mg合金化对Al-Cu-Li合金时效特性和显微组织的影响

通过力学性能测试和显微组织观察研究微量Ag和Mg对Al-3.5 Cu-1.0Li合金时效特性和显微组织的影响.结果表明:在175℃时效时,单独加Ag不影响合金的时效硬化效果,析出物形貌与Al-Cu-Li合金相似,峰值时效状态下均析出较粗大的T1相和θ'相;单独加Mg加快Al-Cu-Li合金的时效响应,提高合金的时效硬化效果,时效时析出GP区,θ'相和T1相;Ag和Mg同时添加的2050合金中,T1相的析出速度加快,析出密度增大,并以T1相为主要强化相,时效强化效果最大.Ag,Mg添加对合金的不同影响可通过溶质原子与空位、溶质原子与溶质原子之间的相互作用来解释.     

Mg、Zn在2099铝锂合金中的微合金化作用

研究Mg、Zn添加对一种Al-Cu-Li合金微观组织演变及力学性能的影响。结果表明,Mg、Zn的添加促进了δ′相的形核析出,并且可以降低其长大速度,因而使得合金中的δ′相更加细小弥散。在时效早期,含Mg和Zn的合金中析出大量的GP区,而不含Mg只含Zn的合金中没有看到GP区的存在,只有少量粗大的θ′相;含Mg不含Zn的合金中也有较多的GP区生成,这说明Mg促进GP区的形成,Zn单独作用对GP区形成无太大影响,只有和Mg一起作用时起到加速GP区形成的作用。随着时效的进行,含Mg和Zn的合金中GP区转变成θ′/θ′′相,而不含Mg只含Zn的合金中θ′相无明显变化,含Mg不含Zn的合金中也有大量θ′/θ′′相生成。说明Mg是促进θ′/θ′′相形成的主要元素,而Zn只是在有Mg的存在下起到促进其形成的作用。     

铝合金时效过程(下)

1.Al—Cu和Al—Cu—Mg合金众所周知,Al—Cu合金的时效过程:α过饱和固溶体→GP(1)区→GP(2)区(θ″)→中间相θ′→稳定相θ。关于GP(1)区和θ″相的精细结构,许多学者采用各种手段做了大量研究工作。Guinier根据X射线衍射情况,对时效初期析出物的精细结构做了推论,认为GP(1)区是Cu原子富集在5层原子层上,G.P(1)区中晶面间距缩小10%;Gerold认为GP(1)区是由纯Cu原子组成的1层原子层,波及15层原子层,畸变     

Al-Cu合金时效初期的价电子结构

用固体经验电子理论(EET)对Al-Cu合金时效初期的析出相的价电子结构进行计算.计算结果表明:合金基体析出的共格GP区、θ″相,具有比基体更强的共价键络,提升了合金的整体键络强度.从价电子结构层次上解释了时效初期的GP区和θ″相对合金强化作用的内在原因.     

连续冷却对7020合金组织与性能的影响

采用扫描电镜和透射电镜观察、电阻率和硬度测试等手段,研究连续冷却条件对7020合金时效组织性能的影响,并绘制实验合金的CCT图。结果表明:实验合金的连续冷却脱溶产物主要包括GP区、η′相和η相,高温阶段主要对应η相在弥散粒子、晶界等异质形核质点上的优先析出,中温阶段主要对应η相在基体内均匀析出,低温阶段则主要对应GP区、η′相的析出,实验合金的临界冷却速率达到700℃/min以上。不同冷却条件引起析出相组态的变化,导致合金的硬度和电阻率随冷却速率降低而发生相应的变化。较慢冷却速度下的脱溶会消耗溶质原子,从而导致时效驱动力下降,而合适的冷却速率下形成的亚稳相则可作为时效强化相的前驱体,能够加速时效强化相析出,导致合金的时效硬化曲线峰值时间提前。     

Al—3.5Cu和Mullite／Al—3.5Cu复合材料的时效析出行为

用差示扫描量热仪（DSC）对Al-3.5Cu合金和莫来石（Mullite)短纤维增强Al-3.5Cu复合材料的时效析出行为进行了研究。结果表明,Al-3.5Cu合金和Mullite/Al-3.5Cu复合材料固溶淬火试样的DSC扫描曲线存在较大不同,GP区形成的溶解的信息在基体合金的DSC曲线上清晰可见,但在复合材料固溶淬火试样的DSC曲线上则很难确认,表明纤维推延或抑制了GP区的形成。θ^〃相和θ′相的析出过程由于纤维的引入而得到明显加快,峰值温度降低,激活能减小,时效析出过程加快。但是,扫描参数选择不当时,容易对析出相的析出过程产生错误判断,应引起重视。     

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.