退火过程中AA3003铝合金的析出行为

通过硬度、电阻检测以及光学显微镜、透射电镜观察,研究了AA3003铝合金在退火过程中的析出行为以及对合金显微组织的影响.结果表明:低温阶段(＜450℃),大的冷轧变形量将导致更多的析出;在高温阶段(＞450℃)时的析出与冷轧变形量无关;在300℃退火时,析出发生在再结晶之前,导致晶粒粗大;而在500℃退火时,再结晶发生在析出之前,可获得细小的等轴晶.对于铝电解电容器用AA3003铝合金阴极箔的生产,宜采用500℃,30 min中间退火制度,这样既可以保证大量弥散相的析出,又可以获得细晶组织,有利于提高阴极箔比的电容.     

箔材用3003铝合金的热处理和性能

采用金相显微镜、扫描电镜、透射电镜和拉伸试验机等研究了预回复退火、一段中间退火和两段中间退火后箔材用3003铝合金的显微组织和力学性能。结果表明:随着退火温度的升高,3003铝合金的电导率先上升后下降,锰原子的固溶度先减小后增大; 450℃退火的3003铝合金的电导率最高、锰原子固溶度最小、析出相密度最高; 3003铝合金退火过程中的析出相主要为针状Al_6Mn相、粒状Al_(12)(Fe,Mn)_3Si相和块状Al_6(Fe,Mn)相。预回复退火有利于中间退火后的3003铝合金形成细小的等轴晶粒。一段中间退火和两段中间退火后3003铝合金的塑性应变比各向异性Δr值分别为0. 31和0. 03,即450℃×5 h+525℃×15 h两段中间退火有助于消除3003铝合金板的平面各向异性,从而有效避免3003铝合金板在深冲成箔材的过程中产生制耳。     

预退火处理对等通道转角挤压双辊铸轧AA3003铝合金显微组织演变的影响（英文）

添加少量锆元素对双辊铸轧AA3003铝合金进行改性。在450℃对合金进行退火处理产生Al_3Zr析出相,同时出现富Mnα-Al(Mn,Fe)Si相。由等通道转角挤压引起的大塑性变形致使合金的晶粒细化且硬度增加。电子背散射衍射及透射电镜观察结果显示在热处理变形后期预先退火处理对合金显微组织变化的影响。对于变形前未进行退火处理的合金,在450℃退火时,其位错回复和α-Al(Mn,Fe)Si相析出使再结晶提前发生。由于预变形退火使固溶体中Mn原子含量降低,因此,在变形过程中对合金进行预变形退火处理会使回复更容易发生。Al_3Zr析出相能促进再结晶过程的进行。     

3003-H16铝合金卷材生产过程中的组织演变

利用热分析仪、光学显微镜、扫描电镜和能谱仪等方法研究了3003-H16铝合金卷材生产过程中的组织演变。结果表明,晶粒尺寸、二次枝晶间距和金属间化合物尺寸从铸锭心部至铸锭表层逐渐减小。当均匀化温度为590 ℃时,α-Al晶体内析出细小颗粒状的Al₆Mn;随均匀化温度的提高,颗粒状析出相不断溶解并促进针棒状析出相长大;当均匀化温度为640 ℃时,针棒状析出相开始溶解,至650 ℃时完全溶解。金属间化合物Al₆(Fe,Mn)和Al₆Mn随均匀化温度的升高而变得圆滑球化,部分Al₆(Fe,Mn)在均匀化过程中转变为Al(Fe,Mn)Si。3003铝合金热轧卷材的晶粒组织在厚度方向上存在不均匀性,冷轧和中间退火后有所改善。3003铝合金卷材中的化合物沿轧制方向成行排列,具有明显的方向性,其中大尺寸化合物的比例随加工率的增大逐渐降低。均匀化可以改善3003铝合金的成分和组织均匀性,改善合金的塑性。变形加工在提高3003铝合金强度的同时降低了合金的塑性。中间退火过程中纤维状的变形组织转变为再结晶组织,消除了硬化现象,合金的塑性得到改善。     

冷轧变形量及退火温度对3003铝合金箔组织性能的影响

利用常温拉伸试验结合偏光组织分析,试验研究了两种冷轧变形量制备的3003铝合金箔材组织和性能随退火温度的变化规律。并通过高温下垂试验结果分析,确定出较好的3003铝合金箔材生产工艺制度。结果表明,14.3%冷轧变形量,420℃退火1.5 h,其箔材抗高温下垂性能较好。     

退火工艺对3003铝合金板微观组织与力学性能的影响

研究了退火工艺对3003铝合金板微观组织与力学性能的影响。试验结果表明,3003铝合金板退火后第二相粒子主要为Al₆(Mn, Fe)、Al₆Mn以及在位错或者亚晶界等缺陷处形成的α-Al(Fe, Mn)Si相。随退火温度升高和保温时间延长,第二相粒子发生粗化,并出现了少量的弥散第二相。当退火温度为450 ℃时,第二相又重新固溶到基体。随退火温度升高,3003铝合金板硬度稳定在31.0 HV0.5 左右,抗拉强度整体上呈下降趋势,伸长率呈增加趋势。     

等温退火过程中AA3003冷轧铝合金的析出行为

通过电导率测试、硬度试验、偏光显微镜以及透射电镜的观察,研究不同冷轧变形量下AA3003铝合金在等温退火(350~500℃)过程中的析出行为及其对合金显微组织的影响。结果表明:随着变形量的增大,最佳析出温度明显地由高温向低温移动,降幅超过100℃;冷轧变形促进析出,且随退火温度的升高其促进析出的能力逐渐减弱;尤其在高温段(450、500℃)等温退火时,析出峰的移动以及再结晶的影响致使电导率曲线的位置随冷轧变形量的增大而出现上下波动的现象;析出粒子的形核位置也会受到再结晶的影响。     

中间退火前后冷轧变形量对3003铝合金阴极箔比电容的影响

采用扫描电镜及能谱仪,透射电镜和比电容检测等方法研究了中间退火前后冷轧变形量对3003铝合金阴极箔第二相分布及比电容的影响.结果表明:随着最终冷变形程度的增加,位错密度增大,从而比电容值显著提高;最终冷轧变形量为90%时,比电容达到最大值,继续增加冷轧变形量,比电容值反而下降;但对于最终冷轧变形量95%的箔材,由于中间退火前冷轧变形量较低,使得退火过程中析出的弥散第二相数目减少,最终导致成品箔中的腐蚀位置减少,比电容降低.     

均匀化退火对3003铝合金冷轧板组织的影响

利用OM、SEM及EDS等手段,研究了均匀化退火对电解铝液直接铸轧3003铝合金冷轧板显微组织的影响。结果表明,均匀化退火前的3003铝合金冷轧板组织中存在较多粗大的针片状FeAl3相,少量圆颗粒状(Fe,Mn)SiAl相及短棒状(Fe,Mn)Al6和MnAl6相;均匀化退火后,Mn从过饱和固溶体中析出,置换FeAl3中的部分Fe而形成大量(Fe,Mn)Al6相,针片状FeAl3相明显减少,同时在晶间析出大量圆颗粒状(Fe,Mn)SiAl及短棒状MnAl6相。     

中间退火与冷轧压下率对3003铝合金组织及抗下垂性能的影响

采用光学金相显微镜、电子万能力学试验机、抗下垂试验等测试手段,研究了中间退火、冷轧压下率对3003铝合金薄板和箔材组织及钎焊抗下垂性能的影响。结果表明:3003铝合金H14态薄板的再结晶晶粒尺寸明显大于H18态薄板的再结晶晶粒,且350℃以上温度退火,强度变化不大;冷轧压下率较小时,随着压下率增加晶粒尺寸迅速减小,压下率40%以上时,随着变形量增加,再结晶晶粒尺寸减幅不大; 3003铝合金箔材钎焊后的晶粒尺寸随压下率的减小而显著增大,冷轧压下率为20%～25%时抗钎焊下垂性能最佳。     

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).     

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.     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.