高速干车削300M钢表面粗糙度及残余应力研究

针对高强度钢300M在高速切削时加工质量不稳定的切削特点,对其进行高速干车削试验,研究切削参数对加工表面粗糙度和残余应力的影响,结果表明:进给量对加工表面粗糙度Ra的影响最大,且随着进给的增加,加工表面残留材料高度差变大,加工质量变差;加工表面进给和切削方向的残余应力均为压应力,切削速度和切削深度对残余应力的影响较大;在vc=300~400 m/min、f=0.15~0.20 mm/r、ap=0.10~0.15mm的切削条件加工时,可以获得较低的加工表面粗糙度和较大的表面残余压应力。文中的研究对高强度钢类难加工材料的加工工艺优化及高可靠性起落架零部件的制造具有理论指导意义。     

叶片数控加工表面粗糙度控制的研究

分析叶片数控加工中影响表面粗糙度的主要因素,推算出插补与走刀步长、加工残留高度的计算公式,并分析其余切削参数对表面粗糙度的影响,在实际应用中具有指导意义.     

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。     

CVD涂层刀具高速铣削天然大理石表面粗糙度研究

为了提高大理石加工表面质量,改进表面粗糙度,通过设计正交试验方案,进行CVD涂层刀具高速铣削天然大理石试验,检测加工表面粗糙度,分析天然大理石表面粗糙度随着单一切削参数的变化规律,并基于经验公式,以切削速度、切削深度及进给速度为影响因素建立加工大理石表面粗糙的预测模型。通过试验得到大理石表面粗糙度随着切削速度的增加而降低,随着进给速度和切削深度的增加而增加。结果表明:预测模型具有较高的显著性,为优化切削参数以改善加工大理石表面质量提供一定的参考;切削深度是影响加工大理石表面粗糙度的主要因素。     

加工参数对单晶γ-TiAl表面质量和亚表层损伤的影响机理

为研究加工工艺参数对纳米切削单晶γ-TiAl合金表面质量和亚表层损伤的影响机理,以分子动力学（molecular dynamics, MD）为基础理论,采用非刚性金刚石刀具建立三维纳米切削模型,通过研究切屑体积、表面粗糙度、静水压分布、位错密度、位错演化、相变原子数,详细分析不同切削速度和切削深度对表面和亚表面结构的影响。结果发现:随着切削速度的增加,切屑体积增大,加工效率提升,且存在切削速度为100 m/s的临界值。表面粗糙度先减小后增大,同样存在切削速度为100 m/s的临界值。位错的复杂程度降低,位错密度减小,塑性变形程度增加;随着切削深度的增加,切屑体积增大,加工效率提升,表面粗糙度、位错密度以及塑性变形程度显著增加。在切削过程中,发现位错主要分布在刀具前方和下方,在刀具前方45°方向存在V形位错和梯杆位错以及位错间的相互反应,且切削完成后残留下空位和原子团簇等稳定缺陷。      

氢化锂材料车削表面粗糙度预测模型的建立

文章主要介绍了运用回归分析方法建立氢化锂车削表面粗糙度预测模型的方法。通过所建立的粗糙度预测模型，研究了车削过程中切削速度、进给量、切削深度对表面粗糙度的影响。经加工试验证明了该表面粗糙度预测模型的有效性，从而实现加工前在确定切削条件下预测和控制表面粗糙度的目的。     

车削氧化锆陶瓷轴端面粗糙度的影响因素分析

在用金刚石刀具对氧化锆陶瓷轴端面进行切削加工时,研究各个切削用量对其表面粗糙度的影响。设计多组切削参数,完成氧化锆毛坯轴在不同参数下的切削加工,然后用表面粗糙度仪器对切削后的陶瓷轴端面进行观察和测量。得到表面粗糙度值随切削用量的变化,各切削用量对表面粗糙度的影响程度,以及最优参数下陶瓷轴的表面形貌。最后获得了切削氧化锆毛坯轴端面时的最佳切削用量,在该参数下的表面粗糙度值最小,表面形貌最光整,该研究对实际加工和生产实践具有一定的指导意义。     

一种不锈钢材料车削的表面粗糙度试验与研究

针对不锈钢材料切削加工的难题,采用回归正交表设计试验方案。采用回归方法对试验数据进行分析,建立表面粗糙度模型。利用自编程序迅速、准确地完成试验数据的选取、处理,并进行结果分析。结果表明：切削速度、进给量、车刀刀尖半径对表面粗糙度的影响明显,而切削深度对表面粗糙度的影响不明显;增大切削速度、车刀刀尖半径可降低表面粗糙度,增大进给量会使零件表面粗糙度变大。试验结果对不锈钢的加工有重要的参考价值     

车削钛合金TC4的表面粗糙度预测模型构建

采用中心复合试验对钛合金进行了车削试验,分析了切削三要素切削速度、进给量、切削深度对表面粗糙度的影响。基于二阶响应面法建立了表面粗糙度的预测模型,对回归方程进行了显著性检验,并对切削参数影响表面粗糙度的显著性进行了比较。结果表明:在试验采用的切削参数范围内,进给量对切削表面粗糙度的影响最大,切削深度次之,切削速度影响最小;预测模型回归显著,置信度高,可指导加工前合理切削参数的选择,以达到对表面粗糙度进行预测和控制的目的。     

铣削铝合金表面粗糙度试验研究

由于表面粗糙度对零件的使用性能,如零件的相互配合的稳定性、耐磨性、耐腐蚀性和使用寿命等都有着很大影响,所以它是表面加工质量的一个非常重要评价指标。表面粗糙度的形成机制可以归结为刀具结构以及形状参数等变量、切削参数变量、加工零件的形状或者要求的特殊性和切削过程中惯性等变量因数,然而这些因素的影响又不是单独作用在表面粗糙度上的,彼此存在一定的交互影响,因此,研究在铣削铝合金的过程中刀具几何参数及切削参数变化对表面粗糙度的影响,为铝合金的铣削加工提供理论参考。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.