In对Al-3.5Cu合金析出过程的影响

利用透射电镜(TEM),差示扫描量热仪(DSC)等方法对Al-3.5Cu和Al-3.5Cu-0.5In(质量分数,%)合金中θ′相的生成及粗化行为进行对比研究。在175℃时效时In的添加显著地促进了合金的时效响应,时效峰值硬度提高了约200MPa。TEM观察结果显示富铟(In′)粒子在时效早期均匀析出,为θ′相的析出提供了非均匀形核位置;且在θ′相宽面发现了位于其片状顶角的In′粒子;时效后期含In合金中θ′相粗化速率明显小于无In合金。时效前增加6%预变形后两种合金时效响应及效果差别不大,证实T6状态In主要是通过淬火空位团簇,从而促进θ′相析出。     

Ag对Al-Cu-Mg合金Ω相析出行为的影响

用硬度测试、差热分析(DSC)以及透射电镜(TEM)研究Al-Cu-Mg-(Ag)合金时效过程中组织和性能的演变;根据不同升温速率的DSC曲线,采用Kissinger法计算Ω相和θ'相的激活能,探讨Ag对Al-Cu-Mg合金Ω相和θ'相析出行为的影响.结果表明:Al-Cu-Mg合金经185℃时效后,时效硬化曲线呈双阶段硬化特征,生成少量Ω相;添加Ag后,合金的时效硬化能力显著提高,经170、185和200℃时效时,对应的峰值时效时间分别为10、5和2h,峰值硬度随着时效温度的升高而下降;Ag能促进Ω相析出,使θ'相的激活能提高,从而抑制θ'相的析出.     

Ag对Al-Cu-Mg合金组织与性能的影响

通过硬度测试、拉伸测试和透射电镜(TEM)分析,研究了Ag对Al-Cu-Mg合金室温力学性能与显微组织的影响.结果表明,Ag的添加加速了合金的时效过程,使合金的室温强度得到明显提高.在165℃峰时效时,含Ag的合金析出相是与基体共格的片状Ω相及少量θ'相组成,未含Ag的合金析出相主要是θ'相.Ag促进合金强化的原因在于Ω相具有很好的沉淀强化作用,在长时间时效时具有较好的抗粗化能力.     

Ge对汽车车身板用Al-Mg-Si系铝合金组织和性能的影响

通过相图、第一性原理计算和DSC、TEM等方法,研究了Ge元素对汽车车身板用Al-Mg-Si系铝合金第二相析出行为和合金性能的影响。结果表明:Ge原子比合金中其他原子(Mg、Si、Cu、Mn)具有较低的空位形成能和较强的空位结合能,能促进析出相的形成,有效延缓自然时效现象;Ge元素的添加,使合金的人工时效硬化速率加快,由于基体中更多空位形核中心的出现,使得析出相更加细小弥散,提高合金强硬度。     

预变形对2519铝合金组织与力学性能的影响

通过拉伸测试、显微硬度测试、透射电镜及扫描电镜分析等手段研究了预变形对2519铝合金组织与力学性能的影响.结果表明:预变形降低了合金于180℃时效第一阶段的硬化效果,提高了合金峰值硬度及强度,缩短了峰值时效时间.预变形合金强度、硬度的提高是由于θ′相的数目增加和尺寸减小.细小弥散的θ′相有利于阻碍位错的运动,提高了合金的强度,同时也降低了合金的塑性.综合考虑合金的强度和塑性,2519铝合金时效前的预变形以15%为宜.     

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...     

含微量镁的Al—Zn—Mg合金的高温时效现象

一、绪言过去对含微量镁的Al-Zn-Mg合金的时效现象一些著者只在低温下作了专门研究,大部分是对添加镁使低温时效缓慢的研究。然而这种时效缓慢现象直到最近才认为是由于Mg和原子空位相互作用,即占据空位的结构。例如有的著者认为Mg在时效初期占有过剩的原子空位,Zn扩散时必要的原子空位浓度减少,因而在初期时效速度下降,由于后期消减Zn原子空位时效现象就继续下去。对于这些问题一些作者认为,当在Al-Zn-Mg合金中添加微量Mg时在其时效温度下,合金的组成点从〔α κ(Zn)〕2相区向(α κ θ)3相区移动,其结果在时效中产生差别,这就成为时效缓慢的原因。就是在这种情况下,由于与θ(Mg_2Zn_(11))相对应的G·P区生成的速度缓慢而产生时效缓慢现象,所以占据空位     

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。     

Si对铸态Al-5.3Cu-0.8Mg-0.6Ag合金显微组织与时效析出的影响

通过熔炼铸造法制备了一系列含Si的Al-Cu-Mg-Ag合金,采用金相观察、扫描电镜(SEM)、透射电镜(TEM)及硬度测试,研究了Si的添加对铸态合金的显微组织与时效过程影响。结果表明,高含量Si的添加降低了铸态合金的时效硬度与高温耐热性能,延长了铸态合金在185℃时的峰时效时间,完全抑制了基体合金中强化相-Ω相的析出。含6.0%Si的Al-5.3Cu-0.8Mg-0.6Ag合金的强化相主要由θ′相及少量σ相(Al5Cu6Mg2)组成。     

T6热处理对锻造Al-4.4Cu-0.7Mg-0.6Si合金显微组织及力学性能的影响（英文）

用透射电子显微镜、扫描电子显微镜、硬度及拉伸测试研究时效处理对锻造Al-4.4Cu-0.7Mg-0.6Si合金显微组织及力学性能的影响。结果表明,经170℃时效16 h后,合金力学性能优良,抗拉强度为504 MPa,伸长率为10.1%。当测试温度升高到150℃时,合金的抗拉强度缓慢下降到483 MPa;继续升高温度到200℃以上时,合金强度快速下降。大量θ'析出相及AlMgSiCu四元析出相(Q相)导致合金峰时效的高强度。稳定的细小弥散θ'相使得该合金在150℃下仍保持较优的力学性能;当温度高于150℃时,θ'和Q相的粗化以及θ相的析出导致合金强度的快速下降。     

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.     

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).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。