半固态成形制备铝铅难混溶合金

通过机械搅拌半固态成形技术制备铝铅系难混溶合金.研究了温度对该合金铅颗粒晶粒尺寸和分布及固相率的影响.微观结构观察表明:通过强力的机械搅拌,可以把铝铅合金中的铅颗粒弥散均匀分布于基体合金中.随着温度的降低:合金的固相率增大,从630℃开始凝固到585℃合金固相率升到67%,呈非线性变化;初生α-Al颗粒在机械搅拌的作用下变得圆整;铅颗粒粒度趋于减小,分布分布趋于均匀、一致,与温度之间同样呈非线性变化;合金中铅含量测试表明,铅的含量处于5.80%左右.说明可利用机械搅拌结合半固态成形技术制备铝铅系难混溶合金.     

半固态废弃铝硅合金的稳态流变性能的研究

利用同轴双筒流变仪研究了以废旧铝料为原料的半固态铝硅合金浆料的稳态流变性能.结果表明,半固态铝硅合金浆料的稳态表观黏度随固相分数的增加而增加,但随剪切速率的增大而减小,并得出稳态表观黏度的公式来描述固相率、剪切速率对稳态表观黏度的影响.     

半固态镁合金制浆工艺与组织特征

采用自行设计制造的半固态镁合金机械搅拌装置,制备镁合金半固态浆料,研究了搅拌工艺参数对半固态镁合金组织的影响。结果表明,搅拌速率、静置时间和搅拌温度对半固态组织影响很大,搅拌速率在1 000 r/min时,静置时间为5～10 min,搅拌温度在560～580℃时,获得的组织均匀细小。搅拌速率过大,晶粒尺寸反而有所增大;静置时间影响半固态组织中固相晶粒的长大;搅拌温度影响固相率,从而也影响到固相晶粒的圆整度。     

基于CA-CCA方法定量解析AZ91D镁合金半固态固相率的研究

针对镁合金半固态成形工艺中,初始固相率难以精确确定的问题,以传热学模型和CA-CCA原理为基础,设计制作了一套研究半固态固相率的实验装置,通过实测降温过程中的温度-时间曲线,进行数值解析,实现了半固态固相率与温度定量关系的求解.结果表明,AZ91D合金的固相率对温度的变化极为敏感,且呈非线性关系.当固相率从20%上升至30%时,温度变化仅为6℃左右;而固相率从30%上升至40%时,温度变化仅在7℃左右.因此,对温度进行定量控制是制备高性能AZ91D合金的关键技术之一.     

工艺参数对半固态镁合金表观粘度的影响

通过制备AZ91D镁合金半固态浆料,研究不同剪切速率、固相分数和搅拌时间对半固态镁合金AZ91D表观粘度的影响。结果表明,半固态镁合金表观粘度的大小随固相分数的增加而增加,随剪切速率的增大和剪切时间的延长而降低。在剪切温度570℃左右,其相对应的固相分数fs=0．41时较适合镁合金的半固态流变成形。剪切速率越大,合金浆料到达稳态的时间越短。     

搅拌工艺参数对SIMA法半固态AZ91D镁合金组织的影响

采用自行设计制造的半固态镁合金机械搅拌装置，制备了镁合金半固态浆料，研究了搅拌工艺参数对半固态镁合金组织的影响。结果表明：镁合金半固态等温搅拌温度在570～580℃，搅拌时间为6～9min时，获得的组织均匀细小。搅拌时间过长，晶粒尺寸反而有所增大。搅拌温度影响固相率，从而也影响到固相晶粒的圆整度。     

变温搅拌制备AlSi7Mg合金半固态浆料的研究

采用变温机械搅拌方法制备Al Si7Mg合金半固态浆料,研究了冷却速度、剪切速率对浆料组织的影响,探讨了强制对流条件下半固态浆料中球状初生相的制备机理。结果表明:在强制对流机械搅拌、剪切速率40 s-1,冷却速度0.12~0.25℃/s以及剪切速率20~80 s-1、冷却速度0.12℃/s条件下制备出近球状组织的Al Si7Mg合金半固态浆料。增加剪切速率对浆料组织形貌影响不大,冷却速度是决定半固态浆料组织形貌的关键因素。强制对流下的合金熔体,在保证合金熔体温度场、溶质场均匀性和合适的冷却速度条件下,初生相就会以球状晶的特定生长方式生长,从而获得满足流变成形的半固态浆料组织。     

剪切力下半固态Sn-52Bi合金组织演变与塑性的研究

采用机械搅拌的半固态铸造技术制备Sn-52Bi合金,探索了不同固相率下剪切力和作用时间对半固态Sn-Bi合金组织和塑性的影响。结果表明,在近液相线的146℃(固相率为4%),搅拌速度为320 r/min和搅拌6 min的工艺条件下,制备出分布均匀、直径约10μm球状初生相的半固态Sn-52Bi合金,其伸长率为31.3%,与在180℃下的合金金属熔液直接水冷凝固而成的相比提高了74.8%。随着剪切力作用时间的延长和半固态合金浆料中固相率的增加,半固态浆料的初生相易发生团聚,所制备的半固态Sn-Bi合金初生相为分布不均的蔷薇形或椭圆形,合金伸长率下降。     

搅拌工艺参数对半固态AZ91D镁合金流变性能的影响

通过自行设计制造的一套半固态镁合金机械搅拌装置，制备了AZ91D镁合金半固态浆料，研究了工艺参数对半固态镁合金流变性能的影响。结果表明，适合镁合金的半固态温度为560～570℃，其相对应的固相体积分数为41％～48％。在剪切速率为79．75s^-1、剪切时间为240s时就可使半固态镁合金获得良好的流变性能。     

SCR工艺参数对A2017半固态合金组织的影响

采用自行设计的SCR实验机制备A2017半固态合金，研究了SCR工艺参数对A2017半固态合金组织的影响。实验结果表明，合金液浇注温度和轧辊冷却水流量共同影响辊靴间隙中半固态合金的固相率，降低浇注温度或者增大冷却水流量，辊靴间隙高固相率合金区间增长，晶粒尺寸变小；减小辊靴间隙或者提高轧辊转速提高合金层流剪切强度，利于枝晶破碎；增大出口半固态浆料冷却速率能有效抑制晶粒继续生长，保留其完整的非枝晶半固态组织。合金液浇注温度为760～780℃，辊靴间隙为4～6mm，轧辊冷却水流量200～300ml／s条件下，SCR技术可获得浆料状A2017半固态合金，凝固后坯料为均匀、细小的非枝晶等轴晶组织，晶粒大小在40～50μm之间，SCR技术是一种制备半固态加工坯料的理想方法。     

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。