喷丸对TC18钛合金拉-拉疲劳性能的影响

分析了TC18钛合金表面喷丸强化所产生的表面形貌、表面粗糙度、表面残余应力和表面层残余压应力场变化及喷丸对拉-拉疲劳性能的影响,并用疲劳裂纹萌生的微细观过程理论合理解释了拉-拉疲劳极限的提高。结果表明:喷丸强化不仅能够明显延长TC18钛合金的高周疲劳寿命,且能使1×107周次下的疲劳极限提高27%。     

表面完整性对马氏体不锈钢疲劳性能的影响

研究了马氏体不锈钢表面喷丸强化后表面粗糙度，表面形貌，表面残余应力和表面层残余压应力场等表面完整性的变化及其对疲劳性能的影响，结果表明：马氏体不锈钢对表面粗糙度比较敏感，经喷丸强化后产生的残余压应力有利于提高疲劳寿命，且采用低喷丸强度时对疲劳性能更加有利。     

表面喷丸强化处理对TC11钛合金疲劳性能的影响

目的改善TC11钛合金的抗疲劳性能。方法采用喷丸表面强化工艺对TC11钛合金进行了表面强化处理,研究了喷丸强化处理、喷丸+二次喷丸强化处理对TC11钛合金试样表面粗糙度、残余应力、显微组织及疲劳性能的影响。结果喷丸处理能够在试样表层引入厚度约230?m的残余压应力场,但同时导致试样表面粗糙度值增加。喷丸后进行表面二次喷丸,试样表面残余压应力值和残余压应力峰值提高,但残余压应力峰值的位置和残余压应力层的厚度变化不大。二次喷丸对试样表面起到一定程度的修复作用,使试样表面粗糙度值降低。喷丸后试样表层组织发生明显的塑性变形,晶粒变细,而喷丸+二次喷丸处理可使试样表层组织得到进一步细化。喷丸处理后,试样的疲劳强度由480 MPa提高至540 MPa,提高了12.5%,二次喷丸使试样的疲劳强度提高至570 MPa,在喷丸的基础上继续提高了5.5%。结论喷丸后对试样表面进行二次喷丸对表层残余应力场的影响不大,二次喷丸主要通过降低试样表面粗糙度值和细化试样表层组织,使试样的疲劳强度得到进一步提高。     

Ti-6Al-4V合金的陶瓷湿喷丸表面强化工艺

采用新型陶瓷湿喷丸强化工艺对 Ti-6Al-4V 合金进行表面处理,研究不同喷丸强度对 Ti-6Al-4V 合金微观组织、形貌及残余应力的影响,并通过拉-拉疲劳试验验证陶瓷湿喷丸的强化效果,分析喷丸前后的断裂机理。结果表明：湿喷丸后的表面粗糙度较干喷丸的低,表面粗糙度、残余应力和应力场深度均随着喷丸强度的增加而增加,最大残余应力达-895 MPa,压应力层深度约为250μm;拉-拉疲劳极限比初始的提高了12.4%。微观组织分析表明,喷丸处理后合金的表层位错密度显著增大,晶粒细化,表面形成超细晶。     

Ti-6Al-4V合金的陶瓷湿喷丸表面强化工艺（英文）

采用新型陶瓷湿喷丸强化工艺对Ti-6Al-4V合金进行表面处理,研究不同喷丸强度对Ti-6Al-4V合金微观组织、形貌及残余应力的影响,并通过拉-拉疲劳试验验证陶瓷湿喷丸的强化效果,分析喷丸前后的断裂机理。结果表明:湿喷丸后的表面粗糙度较干喷丸的低,表面粗糙度、残余应力和应力场深度均随着喷丸强度的增加而增加,最大残余应力达-895 MPa,压应力层深度约为250μm;拉-拉疲劳极限比初始的提高了12.4%。微观组织分析表明,喷丸处理后合金的表层位错密度显著增大,晶粒细化,表面形成超细晶。     

喷丸结合振动光整加工工艺对钛合金疲劳性能的影响

目的提高钛合金的疲劳性能。方法采用喷丸结合振动光整加工工艺对TC4钛合金进行了表面加工处理。对未加工试样、经过喷丸处理后的试样和经过喷丸与振动光整加工工艺处理后的试样,分别进行了表面粗糙度、表面层残余应力测试,并对三种状态下的试样进行了旋转弯曲疲劳试验。对比了不同工艺处理后试样的表面粗糙度、表层残余应力及疲劳强度。结果与喷丸工艺相比,采用喷丸结合振动光整加工工艺对试样进行处理后,试样的表面残余压应力值提高了39 MPa,残余压应力峰值、残余压应力层的厚度略有降低。喷丸结合振动光整加工工艺在不明显改变试样残余压应力场的条件下,使试样的表面粗糙度得到大幅降低。疲劳试验结果表明,喷丸工艺使TC4钛合金的疲劳强度提高了16.3%,喷丸结合振动光整加工工艺使TC4的疲劳强度提高了23.8%,比喷丸后TC4钛合金的疲劳强度高出7.5%。结论在喷丸工艺的基础上,喷丸结合振动光整加工工艺通过改善TC4钛合金的表面完整性,使TC4钛合金的疲劳强度得到进一步提高。     

喷丸强化对23Co14Ni12Cr3MoE钢疲劳性能的影响

采用喷丸强化工艺在23Co14Ni12Cr3MoE高强度钢表面层引入了残余压应力,测定了喷丸工艺下的表面粗糙度、残余应力与疲劳寿命,对比了缺口试样(应力集中系数Kt=2)磨削加工与喷丸状态下的疲劳S-N曲线.结果表明,23Co14Ni12Cr3MoE高强度钢对喷丸强度的要求不同于一般的高强度钢,喷丸强度高时将产生过喷效应,导致疲劳寿命的降低,在优化的喷丸工艺条件下,缺口试样(Kt=2)在1×107循环周次下的条件疲劳极限提高了22%.     

喷丸强化对TC17钛合金疲劳性能的影响

采用铸钢丸对TC17钛合金材料进行了喷丸强化处理,研究了喷丸强化对表面粗糙度的影响,利用X射线应力仪分析强化层残余应力沿厚度方向分布情况,对比分析了TC17试件喷丸强化前后的疲劳性能。结果表明:喷丸对TC17钛合金表面完整性有十分大的影响,喷丸后表面粗糙度Ra由0.3μm增加至1.6μm左右;喷丸后表面残余应力在-600~-700 MPa之间,残余应力场深度达到160μm左右。喷丸可显著提高TC17钛合金的疲劳性能,与未喷丸相比,TC17钛合金喷丸后疲劳极限提高34%以上。     

钛及钛合金喷丸强化研究进展

喷丸强化能够显著提高钛及钛合金材料的常规抗疲劳性能和微动疲劳抗力,在最佳的喷丸工艺条件下可以得到较好的性能.本文从组织强化、应力强化、残余压应力及其松弛、表面粗糙度几方面叙述了钛合金的喷丸强化机制和研究进展.最后阐述了喷丸强化对钛合金力学性能的影响研究.     

ZK60高强度镁合金喷丸强化疲劳性能实验研究

为了研究喷丸强化处理对ZK60镁合金疲劳性能的影响,采用气动式喷丸机对ZK60高强度镁合金试样进行喷丸强化,利用X射线衍射技术对喷丸处理试样表面进行残余应力测试分析,并利用扫描电镜分析了镁合金试样表面晶粒尺寸变化,对所有试样进行疲劳性能测试,分析喷丸强化对ZK60镁合金疲劳性能的影响,同时对疲劳断口进行扫描分析。实验结果表明:喷丸强化在ZK60镁合金试样表面产生了一定的残余压应力分布,且残余压应力最大值可达-198 MPa,同时,喷丸强化可使ZK60镁合金试样表面粗糙度减小,喷丸区域晶粒得到明显细化,喷丸强化使得试样表面完整性得到极大改善,从而提高了ZK60镁合金材料的疲劳性能,喷丸试样疲劳寿命相对于未处理试样最大提高了36%,疲劳裂纹源由试样表面转移到喷丸强化层以内,从而抑制了疲劳裂纹的萌生。     

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。