AZ31镁合金薄板手机外壳温冲模具设计及成形性能研究

设计并制造了AZ31镁合金薄板的手机外壳温冲模具,并对其成形性能进行试验研究。试验表明,eta/DYNAFORM有限元模拟软件能够较好的验证模具设计的合理性和分析AZ31镁合金薄板冲压成形性能,通过合理地选取模具参数,并对拉伸速度、润滑条件、坯料以及凸、凹模温度等主要影响因素的控制,可有效地解决AZ31镁合金拉伸生产过程中的拉裂缺陷,在普通液压机上能成功冲压出镁合金壳形件。     

镁合金手机外壳冲模设计及实验研究

以AZ31B镁合金手机外壳冲模设计和在普通机械式锻压机上的冲压生产为例,对AZ31B镁合金冲压成形过程中的板料制备、冲模设计、模具及板料的温度、冲压变形速度、润滑剂的选用等关键技术作了较为系统的实验研究。实验表明,通过合理地选取模具参数并对拉伸速度、坯料及模具温度等主要影响因素的控制,可有效地解决AZ31B镁合金拉伸生产过程中的拉裂缺陷,在普通机械式锻压机上能成功地冲压出镁合金手机外壳。     

镁合金的冲压模具设计研究

本文以AZ31B镁合金手机外壳的冲压模具设计和在普通机械式锻压机床上的冲压生产为例，对AZ31B镁合金冲压成形过程中的板材制备、冲压模具设计、模具及板材的温度、冲压变形速度、润滑剂的选用等关键技术做了较为隶统的实验研究。实验表明．通过合理地选取模具参数并对拉深速度、坯料及模具温度等主要影响因素的控制，可有效地解决AZ31B镁合金拉深生产过程中的拉裂缺陷。在普通机械式锻压机床上能成功地冲压生产出镁合金手机外壳。     

AZ31B薄板手机外壳温冲试验研究

通过对AZ31B镁合金手机壳的温冲试验研究,分析了凸、凹模温度、镁板温度和加热时间、冲压速度以及润滑条件对成形结果的影响.试验表明,在保证坯料充分退火和模具结构合理的前提下,拉深凸模温度保持在230 ℃,凹模及压边圈温度保持在280～320 ℃,用石墨对坯料凸缘和压边圈、凹模肩部进行有效润滑,同时,施加合适的压边力作用,便可以成功地冲压出镁合金壳形件.     

汽车前防撞梁热成形冷却过程温度场数值模拟

采用ProCAST软件,对高强钢板热冲压成形工艺冷却(淬火)过程进行数值模拟分析,计算了连续多个冲压工作循环下模具和坯料的温度场。结果表明,模具在连续多个冲压工作循环中,温度呈周期性的快速上升和快速下降的变化趋势,当每一个冲压工作循环结束时,模具的温度都保持在50℃左右。坯料在淬火过程中,其温度呈快速降低趋势,冲压结束时坯料的出模温度分布在75℃²25℃上下,出模温度随冲压工作循环的进行而依次略有升高,并达到稳定。对模具和坯料进行试验测试,其温度值与数值模拟值吻合较好,说明该计算模型和方法对成形工艺设计有较好的预测评价作用。     

AZ80镁合金切屑回用的探讨

试验探讨了利用热压．热挤压变形工艺，对AZ80镁合金切屑挤压成棒料再回用，制定了棒料的成型工艺。在压制坯料时，切屑温度为330℃，模具温度为350℃，压力为200MPa。挤压时，坯料温度及模具温度与压制坯料一致。挤压比为25：1，挤压速度为20mm／s。回用棒料经过（200oc＋8h）热处理后，σb为310MPa、σs为230MPa、δ为7％。探讨了AZ80镁合金切屑在热挤压变形成形后的微观组织和力学性能。     

双辊连续铸轧镁合金板材的冲压加工特性

对镁合金连续铸轧薄板冲压零件进行了初步研究.在板坯性能合适的条件下,通过控制工艺环节和工艺参数包括下料温度、预热和加工温度、模具设计、润滑和预热等,发现双辊连续铸轧镁合金板材具有细晶粒和变形组织对变形加工有利.在模具适当预热的情况下,对于低合金化的镁合金薄板不加热,某些类型的零件挤压和冲压也能进行.     

复合形变对AZ31镁合金微观组织及力学性能的影响

对AZ31镁合金板材进行复合形变工艺研究,对比了不同坯料温度、下压量和模具温度对镁合金板材微观组织和力学性能的影响。结果表明,坯料温度为275℃、下压量为29%,模具温度为150℃时,复合形变后镁合金板材拥有理想的微观组织和力学性能。此时镁合金板材平均晶粒尺寸为7.84μm,显微硬度(HV)为91.99,屈服强度为212 MPa,抗拉强度为298 MPa,伸长率为17.2%。     

AZ31镁合金复杂形状壳体拉深成形试验研究

通过拉深成形试验研究了AZ31镁合金复杂形状壳体的成形性能,分析了成形温度、拉深速度、坯料加热时间及润滑等工艺参数对镁合金手枪壳体拉深成形件质量的影响规律.结果表明,合理的成形工艺参数:成形温度为290～350 ℃,拉深速度为0.1～0.2 mm/s,加热时间为5～10 min,润滑剂采用二硫化钼和机油的混合物,成功地加工出合格的复杂形状的镁合金手枪壳体.     

锻压工艺对汽车镁合金棒材性能的影响

采用不同的坯料加热温度、模具温度和锻比对汽车用AZ80镁合金棒材进行了锻造,并进行了不同温度下的力学性能测试与分析。结果表明,随坯料加热温度从440℃提高至480℃或锻比从5增大至9,棒材的抗拉强度、屈服强度和断后伸长率均先增大后减小;随模具温度从320℃提高至360℃,棒材的抗拉强度和屈服强度均先增大后减小,断后伸长率先增大后基本不变。坯料加热温度优选为470℃、模具温度优选为350℃、锻比优选为8。     

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.     

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。