半固态Y112铝合金成形组织与性能

采用近液相线半连续多模铸造法制备出Y112铝合金半固态坯料。分别考察了半固态合金流变成形件、触变成形件和常规压铸件的组织与性能。结果表明：Y112铝合金的半固态流变成形件的组织细小、均匀，硬度为112HV，优于触变成形件和常规压铸件的。     

Al-Mg-Si合金半固态触变成形研究

以水泵盖为目标零件,在自行建立的半固态触变成形试验线上使用A357合金和新开发的半固态专用铝合金Al-6Si-2Mg进行了半固态触变压铸试验研究.对这两种合金在半固态坯料制备、二次加热及半固态压铸中的显微组织及工艺性进行了比较.结果表明,Al-6Si-2Mg合金在触变成形过程中均表现出更好的工艺可控性,其半固态压铸件热处理后的性能为σb=335MPa,σs=305MPa,δ5=3%,强度高于A357,伸长率与铸态A357合金相当.试验最终获得了充型完好、性能优异、组织均匀的半固态压铸件.     

触变成形AlSi7Mg合金的组织与性能

AlSi7Mg合金半固态浆料经触变成形及热处理后,其性能得到显著提高。试验采用电子显微镜、扫描电镜及电子拉伸机,研究了液相半连续铸造法制备的AlSi7Mg合金半固态浆料的组织、二次加热的合金组织、经触变成形及T6处理后的组织与性能。结果表明,触变成形并经热处理后的AlSi7Mg合金,其组织中析出相为Al3Si和AlSi化合物,σb达到290.2MPa,δ5达到12.9%,此结果为液相线半连续铸造AlSi7Mg合金触变成形的深入研究奠定了基础。     

SSTT和RAP方法得到的ZK60镁合金的组织变化和力学性能

研究了分别由半固态热成形方法（SSTT）和部分重熔再结晶方法（RAP）得到的 ZK60镁合金在一定温度下显微组织随等温时间的变化和触变成形试样的力学性能。结果表明,合并长大机制在SSTT合金的组织变化中占主导地位,熟化机制在RAP 合金的组织变化中起主要作用。在相同的等温条件下,与SSTT方法相比,RAP方法可以得到更细小的半固态显微组织,RAP合金组织比SSTT合金组织更圆整。由SSTT方法和RAP方法得到的ZK60镁合金触变成形后均得到了较理想的成形件,触变成形工艺提高了材料的力学性能。与 SSTT 合金相比, RAP合金具有更优越的力学性能。     

ZL116合金的半固态触变成形

采用ZL116合金进行了半固态触变成形试验,结果表明,应用半固态触变成形工艺可以获得组织致密、轮廓清晰、充型完整的成形件;成形件的微观组织主要为细小、分布均匀的近球状和蔷薇状非枝晶组织;成形静压力作用所引起的局部组织塑性变形,使成形件的组织与性能得到改善,与液态触变工艺相比,硬度提高20％。     

汽车发动机缸体的半固态成形工艺研究

对汽车发动机缸体用Al-Si-Fe合金进行了半固态触变挤压成形和T1、T6热处理,研究了不同制备工艺下Al-Si-Fe合金的显微组织、物相组成、力学性能和耐磨性能。结果表明,经过半固态挤压触变成形可以破碎合金中的初生硅和α-Al基体,晶粒组织得到细化;经过触变成形得到的Al-Si-Fe合金的强度和塑性都较铸态合金有明显提高,且经过T6热处理后的强度有所增加,而塑性略有降低;铸态、T1、T6和触变成形态Al-Si-Fe合金的耐磨性能要明显高于A390合金;铸态Al-Si-Fe合金的磨损机制为粘着磨损和磨粒磨损,而触变成形态和T6热处理态Al-Si-Fe合金的磨损机制主要为磨粒磨损。     

Mg-Al-Zn合金半固态坯的制备及触变成形研究

通过新SIMA法制备Mg-Al-Zn合金半固态坯的触变挤压和触变模锻试验以及借助金相显微镜、拉伸试验机等分析手段对Mg-Al-Zn合金半固态坯的制备及触变成形进行了研究.研究结果表明,新SIMA法中的等径道角挤压能使Mg-Al-Zn合金获得良好的应变诱导效果,即铸坯微观组织被大大细化,平均晶粒尺寸达到20μm,材料力学性能大幅度提高;该坯料在560℃保温20min制备的半固态坯料的固相晶粒细小,球化程度高,组织均匀,平均晶粒尺寸为25μm.通过触变挤压和触变模锻试验证明,新SIMA法制备的Mg-Al-Zn合金半固态坯料所触变成形的零件的力学性能很高.其中触变挤压的卫星角框零件的屈服强度、抗拉强度和伸长率分别为213.1MPa、312.6MPa和15.2%.触变模锻的托弹板零件的屈服强度、抗拉强度和伸长率分别为218.6MPa、320.9MPa和14.8%.     

铝合金半固态加工技术的应用研究

重点介绍了近年来在铝合金半固态坯料制备方面的研究进展以及在半固态触变成形技术工业应用方面的研究开发工作,如复合电磁搅拌制备半固态浆料、多流电磁搅拌半固态连铸技术、铝合金半固态触变压铸成形、铝合金半固态触变模锻成形等,并就其可能的应用领域及发展状况如难铸造合金的铸造成形、变形合金的直接铸造成形、活塞合金的加工成形、变形铝合金的塑性加工进行了讨论。     

新型半固态用铝合金的触变成形研究

研究了Al-6Si-2Mg半固态成形中,电磁搅拌连铸、二次加热和压铸的工艺以及各工序得到的微观组织和力学性能.由于该合金是针对半固态触变成形专门设计,所以该合金在各工序中都表现出良好的工艺性能.通过优化工艺,试验最终得到了外观完整,性能优良的压铸件,为半固态触变成形的工业应用打下了基础.     

新型倾斜板技术制备半固态铝合金坯料和浆料

采用自行设计的波浪型倾斜板,在斜板冷却条件下制备了组织和触变性能优良的半固态合金坯料。而在斜板加热条件下制备出了组织优良的半固态合金浆料。在采用波浪型的倾斜板制备半固态合金过程中,在熔体爆发形核与枝晶破碎的共同作用下,形成了细小球形的半固态合金组织,浇注温度、冷却强度、斜板倾角和斜板表面材质是影响半固态合金组织的主要因素。得出了本试验条件下制备AlMg3合金半固态坯料的浇注温度范围为660~690℃;制备AlSi6Mg2合金半固态坯料的浇注温度范围为660~680℃;制备AlSi6Mg2半固态合金浆料的合理工艺条件为:斜板预热温度为300℃时,合金浇注温度为680℃。     

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。