超声振动铣削2A12表面粗糙度实验研究

利用小径立铣刀对铝合金进行超声振动铣削实验,重点探讨了超声振幅与每齿进给量对工件槽底表面粗糙度的影响.实验结果表明:槽底表面粗糙随着超声振幅的增大而增大,在每齿进给量fZ<4μm/z时槽超声振幅为主要影响因素;每齿进给量fZ>6μm/z时每齿进给量为主要影响因素.在超声振动铣削加工中应尽量选择小进给量可获得较小槽底表面粗糙度.通过扫面电镜对工件微观形貌观测证实了施加振动后脉冲切削和断续切削双重作用导致槽底表面粗糙度增大.     

超声振动辅助铣削加工实验研究

通过实验研究了超声振动辅助铣削加工参数和振动参数对切削力与表面粗糙度的影响。在工件上施加沿进给方向的高频率、小振幅的超声振动。通过切削轨迹研究了超声振动切削的瞬时切削厚度,进而分析了切削力。以主轴转速、每齿进给量和振幅为参数,设计了一系列超声振动辅助铣削加工实验,并利用方差分析方法研究了各参数对切削力影响的显著性。研究结果表明:与未施加超声振动相比,施加超声振动后的切削力明显降低;超声振动铣削加工时对切削力的影响程度由大到小依次为振幅、主轴转速、每齿进给量;在特定的参数下,表面粗糙度也有所改善;表面形貌在同一振幅、不同进给量下存在明显差异。     

不同PCBN刀具车削硼铸铁的对比研究

使用不同的立方氮化硼刀具材料(PCBN)和刀具结构,在相同加工参数下,对硼铸铁进行切削加工试验,并对比其加工效果。结果表明:同粗粒度的PCBN刀具相比,细粒度的PCBN刀具加工所得的工件表面粗糙度较低,且刀具本身的耐磨性较高;在切削过程中,随着进给量的增大,工件表面粗糙度也增大;PCBN刀具的负倒棱宽度对加工硼铸铁的切削温度和后刀面磨损有较大影响,负倒棱宽度增加,切削温度和刀具磨损增加,而倒棱角度对刀具和切削过程影响有限。     

金刚石钻磨头超声振动钻磨硬脆材料表面质量的试验研究

硬脆材料以其优良的性能在生产实践中得到了广泛应用，但其低塑性、易脆性及不导电性等使得加工十分困难，尤其是超精密表面制作更加困难。为此，本文将超声振动引入普通钻磨中，介绍了超声振动切削原理，通过超声与普通两种方式下的表面粗糙度试验和微观形貌观察得出以下结沦：1）不同加工参数时，超声振动钻磨时的工件表面粗糙度值均低于普通钻磨时的表面粗糙度值；2）随着进给量、工件转速和输入功率的增加，超声和普通钻磨时的表面粗糙度均呈上升趋势；3）普通钻磨加工后孔壁表面有宽度和间距不均匀的沟槽，并且沟槽较宽，而超声钻磨加工后表面沟槽（划痕）较浅且均匀。     

纵-扭复合振动超声深滚加工表面强化研究

目的基于纵-扭复合振动超声加工和超声深滚加工提出了纵-扭复合振动超声深滚加工工艺,研究各深滚工艺参数对工件表面强度的影响,以验证二维超声振动加工技术在表面强化技术领域的应用效果。方法采用单因素试验法对6061-T651铝合金轴件分别进行纵-扭复合振动超声深滚与常规深滚加工试验,然后用MH-5数显硬度计测试每组参数下的表面显微硬度,研究静压力、工件转速和进给量对工件表面显微硬度的影响,并将两种试验结果进行对比。结果在设定工艺参数内,纵-扭复合振动超声深滚工艺所获得的表面显微硬度均高于同等加工条件下常规深滚工艺。纵-扭复合振动超声深滚加工时,表面显微硬度随静压力和工件转速的增大先增大后减小,随进给量的增大先减小后增大再减小;常规深滚加工时,表面显微硬度与静压力近似呈线性关系,且随工件转速的增大先增大后减小,随进给量的增大一直减小。结论纵-扭复合振动超声深滚加工工艺能更有效地实现6061-T651铝合金的表面强化处理。     

二维超声振动磨削纳米复相陶瓷的表面粗糙度研究

本文对纳米复相陶瓷材料进行了不同参数下的普通磨削和二维超声振动磨削的对比试验，研究了超声振动磨削对工件表面质量的影响，分析了不同的加工工艺参数及振动参数对加工工件表面粗糙度的影响，实验结果表明，在同样的切深条件下，超声振动磨削表面的沟槽浅而宽，可以得到比普通磨削加工粗糙度较小的加工表面，且在超声振动中砂轮作高频振动，砂轮不易堵塞，利于使用细粒度砂轮磨削；工件速度对二维超声振动磨削表面粗糙度影响很大，其值随着工件速度的增加而增大。二维超声振动磨削可以提高陶瓷材料的表面质量，并能有效地避免普通磨削下微裂纹的产生，因此它是磨削陶瓷的一种精密加工方法。     

漂珠/镁合金可溶复合材料切削加工表面粗糙度及其预测模型

为研究漂珠/镁合金可溶复合材料的切削加工质量,采用正交试验法对漂珠/镁合金可溶复合材料进行了不同切削参数下的切削加工试验。研究结果表明:进给量对切削加工表面粗糙度影响最大,其次是切削深度,切削速度影响最小;试样表面微观形貌呈平行沟槽状,且其深度和宽度随粗糙度的增大而增大;进给量通过影响试样表面相邻锯齿峰之间的宽度影响试样表面粗糙度;运用回归分析法建立了漂珠/镁合金可溶复合材料切削加工表面粗糙度预测模型,并通过方差分析和实验验证表明模型拟合良好,可以实现对复合材料切削加工表面粗糙度的预测和控制。     

针对表面粗糙度和刀具振幅的切削用量优化研究

对进给量、切削速度和轴向切深这3个切削参数对工件表面粗糙度和刀具振动幅度的影响进行试验研究。采用BBD响应面法对6061铝工件进行端铣加工试验,并通过数学建模对试验结果进行分析。提出一种基于遗传算法的多目标优化方法来同时减小工件表面粗糙度和刀具振动幅度。建立能预报表面粗糙度和刀具振动的径向基神经网络模型,并通过试验验证其准确性。     

二维超声振动车削6061铝合金圆筒表面粗糙度研究

目的 研究分析二维超声振动车削加工中切削参数和声学参数对6061铝合金圆筒表面粗糙度的影响。方法 结合二维超声振动特性,建立二维超声振动车削表面粗糙度理论模型,采用四因素四水平正交试验,获得二维超声振动车削6061铝合金圆筒过程中切削参数和声学参数对工件表面粗糙度的影响规律,选取其中4组进行二维超声振动车削与普通车削对比实验,并通过白光干涉仪和超景深显微镜对加工后的工件表面进行观测。结果 正交试验结果表明,切深对加工表面粗糙度的影响不明显,超声振幅、转速、进给量对加工表面粗糙度的影响程度分别为84.35%、11.36%、4.29%。超声和无超声对比实验表明,二维超声振动车削相较于普通车削能显著降低车削表面的粗糙度,最大下降率为47.65%,最小下降率为11.27%;相比于普通车削加工,二维超声振动车削表面具有均匀分布的鱼鳞状微织构。结论 加工参数对表面粗糙度影响的显著从高到低为超声振幅>转速>进给量>切深,最优加工参数为f_r=0.15 mm/r、n=400 r/min、A=2μm、a_p=0.2 mm。采用二维超声振动车削的加...     

PCBN刀具高速铣削TC4钛合金切削性能与工艺参数优化研究

针对钛合金TC4(Ti-6Al-4V)的加工特性,采用PCBN刀具,基于单因素试验,研究高速铣削条件下工艺参数对切削力、切削振动等的影响规律,提出综合考虑切削力、切削振动、表面粗糙度的工艺参数优选方法。研究表明:切削力和切削振动随切削速度v和每齿进给量f_z的增大呈现一定的波动,随径向切深a_e和轴向切深a_p的增大而增大,切削振动受切削力影响较为显著。考虑切削性能,以材料切除率为优化目标,以切削力、切削振动和表面粗糙度等为约束条件,建立工艺参数优选模型,可得到不同约束条件下工艺参数的优选组合。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.