钛对7050铸轧板材裂纹调控的影响

本文采用场发射高分辨扫描电子显微镜,差示扫描量热仪,X射线衍射仪等先进设备研究了微量Ti元素对7050铝合金铸轧薄板裂纹形成的影响规律和调控机理,结果表明：微量的Ti可以显著细化铸轧板的晶粒组织,改变晶粒生长方式,改善合金的流动性,使铸轧组织更加致密,消除合金内局部应力集中,抑制铸轧裂纹出现。而且,适量Ti元素还可以缩短铸轧7050铝合金的固液相线区间,减小晶核凝固前沿温度梯度,有效抑制成分偏析,从而降低晶界低熔点化合物数量,减少粗大第二相的产生,从而大幅增强铸轧铝合金的抗热裂能力。当7050铸轧板中Ti含量达到0.2%时,Ti对铸轧板裂纹的抑制作用最佳,而过量的Ti元素会聚集形成大块的含Ti脆性相,反而破坏组织的致密性,促进裂纹的萌生。     

铸轧工艺参数对改良型3102D铝合金铸轧板高倍组织的影响

根据3102铝合金的特点及其铸轧板的质量要求,用电解铝液生产改良型3102D铝合金铸轧板,在熔炼炉内固体料占比、辊缝、嘴辊间隙、铸嘴开口度、前箱温度、前箱液位保持不变的情况下,试验研究铸轧区长度、铸轧速度、冷却强度对其组织的影响.结果 表明:3102D铝合金铸轧板的最佳工艺参数为铸轧区长度66 mm,铸轧速度980 m...     

汽车用6063铝合金铸轧过程数值模拟

利用有限元方法对6063铝合金铸轧成型工艺中铸轧区的温度场及速度场进行了数值模拟,确定了合理的浇注温度及铸轧速度参数。模拟结果表明:对于轧辊直径为300 mm的上注式铸轧机,最佳的铸轧工艺参数为浇注温度690℃,铸轧速度10 m/min。该工况下对应的液穴深度为12 mm。     

双辊铸轧薄带钢侧封板热应力的数值分析

采用有限元法模拟了双辊铸轧薄带钢工艺中侧封板的三维温度场和热应力场。通过对侧封板的温度和应力的耦合数值模拟 ,得出了在铸轧过程中侧封板的温度和热应力的分布规律。根据热应力分析了侧封板裂纹产生机理 ,得出侧封板产生裂纹的位置与实验结果相吻合 ;同时分析了不同预热温度对侧封板温度和热应力分布的影响 ,得出了侧封板的最佳预热温度范围     

热处理对汽车用6063铝合金铸轧板显微组织及力学性能的影响

研究了热处理工艺对6063铝合金铸轧板显微组织及力学性能的影响,并深入探讨了固溶及时效处理对其作用机理。研究表明:合理的固溶及时效处理有助于改善6063铝合金的显微组织,且能够显著增加材料的抗拉强度及硬度。热处理工艺为525℃固溶1 h,水淬后175℃时效4 h,可使抗拉强度达到252 MPa,硬度可达115.62 HV。该工艺对应的断裂机制为韧性断裂。     

某型炮塔T形接头焊接残余应力分析

某型铝合金炮塔侧面装甲板底部出现裂纹,裂纹对装备的使用寿命具有一定影响。利用有限元软件ANSYS,采用间接耦合方法对T形接头进行焊接模拟,分析焊接对裂纹产生的影响。在焊接过程中,炮塔侧面装甲板在厚度方向上受热不均匀,热影响区焊接变形受到约束,冷却后侧面装甲板在厚度方向上横向残余应力较大容易导致层状撕裂。仿真结果与实际情况相近,为分析炮塔裂纹产生原因提供了指导。     

Mn添加对双辊铸轧6061铝合金组织和性能的影响

研究了添加Mn对双辊铸轧6061铝合金铸轧板中富铁相转变及力学性能的影响。结合热力学模拟、金相显微镜(OM)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)等手段分析6061铸轧板中富铁相转变及力学性能变化规律;利用室温拉伸试验机测试铸轧板力学性能。结果表明:当ω(Mn)=0.36%(质量分数)时6061铸轧板中富铁相完全由针状β-Al_5FeSi相转变为颗粒状α-Al_(12)(FeMn)_3Si相,当ω(Mn)=0.54%时板材内部出现大量无规则块状与花瓣状α-Al_(15)(FeMn)_3Si_2相聚集,从而显著改善了铸轧板中富铁相形貌;当ω(Mn)=0.36%时,6061铸轧板力学性能最佳,此时抗拉强度、屈服强度和伸长率分别为195.93 MPa、170.36 MPa和17.96%。     

Mn添加对双辊铸轧6061铝合金富铁相转变影响的研究

本文研究了添加Mn对双辊铸轧6061铝合金铸轧板中富铁相转变及力学性能的影响。结合热力学模拟、金相显微镜（OM）、扫描电子显微镜（SEM）及透射电子显微镜（TEM）等手段分析6061铸轧板中富铁相转变及力学性能变化规律;利用室温拉伸实验机测试铸轧板力学性能。结果表明：当ω（Mn）=0.36 wt.%时6061铸轧板中富铁相完全由针状β-Al5FeSi相转变为颗粒状α-Al12（FeMn）3Si相,当ω（Mn）=0.54 wt.%时板材内部出现大量无规则块状与花瓣状α-Al15（FeMn）3Si2相聚集,从而显著改善了铸轧板中富铁相形貌;当ω（Mn）=0.36 wt.%时,6061铸轧板力学性能最佳,此时抗拉强度、屈服强度和伸长率分别为195.93 MPa、170.36 MPa和17.96%。     

薄壁扇形筋板反挤压成形应力转移法

对6063铝合金复杂腔体零件中薄壁扇形筋板反挤压成形过程进行了模拟分析,发现扇形筋板的两端过渡圆角处易产生应力集中,从而导致开裂.增大凸模圆角可以有效降低筋板内的拉应力峰值,并使拉应力均匀分布,但该方法不符合现阶段工艺要求.因此,基于筋板中部切口应力集中现象提出了一种应力转移法,通过该方法改变了筋板内拉应力的分布形态,...     

铸轧铝板的组织及其缺陷 1

根据双辊铸轧机生产铝及铝合金铸轧板的结晶条件，介绍了铸轧板的组织特点；简述了用铸轧板坯料生产冷轧板和箔材的工艺特点及成品特性；着重阐述了铸轧板常见的组织缺陷，产生原因，对成品的影响及其防止措施。     

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。