热处理温度对TiNiCuCo合金的力学性能和形状记忆效应的影响

通过真空感应熔炼制备TiNiCuCo形状记忆合金铸锭,然后经锻造、轧制、热拉拔得到准0.5mm的线材,最后对线材进行300~700℃退火。通过拉伸试验和弯曲回复法等研究了不同温度热处理后TiNiCuCo合金的力学性能和形状记忆效应。结果表明:在300~500℃进行热处理,TiNiCuCo合金的抗拉强度和伸长率几乎不发生变化;在600~700℃进行热处理,其抗拉强度显著降低,伸长率显著增大。随着热处理温度的升高,平台应力先减小再增大。在热处理温度为500℃时平台应力最小,为32MPa。平台应变在300~400℃热处理几乎不发生变化,最大值为6.8%。随着热处理温度的升高,平台应变逐渐减小,700℃时平台应变为3.5%。TiNiCuCo合金在300~500℃热处理后具有良好的形状记忆效应;6%~8%弯曲应变后,合金的最大形状回复率可达96%以上。高于500℃进行热处理,合金的最大形状回复率降低。TiNiCuCo合金对温度的响应程度几乎不随热处理温度发生变化。     

退火工艺对挤压成型镁锰钛合金壳体磨损和腐蚀性能的影响

采用不同工艺对某新型挤压成型Mg-Mn-Ti合金壳体进行了退火热处理,并进行了磨损和腐蚀性能的测试与分析。结果表明:随热处理温度从260℃提高到380℃或热处理时间从2 h延长到8 h,合金壳体的磨损和腐蚀性能都先提高后下降。与260℃热处理相比,320℃热处理时合金壳体的磨损体积减小44%、腐蚀电位正移182 m V;与2 h热处理相比,5 h热处理时机械壳体的磨损体积减小41%、腐蚀电位正移162 m V。合金壳体的热处理温度和时间分别优选为320℃、5 h。     

大型透平机壳焊后热处理的残余应力数值模拟

采用热-粘弹塑性有限元模型,在考虑蠕变效应的基础上,对大型透平机壳进行焊后热处理数值模拟.结果表明,焊后机壳残余应力较高,部分节点超过材料的屈服强度;经过热处理后,机壳整体残余应力均低于材料的屈服强度.在300℃去应力退火,机壳残余应力降低幅度不大;当退火温度升到550℃时,机壳应力降低显著.     

激光沉积修复金属去应力退火局部热处理工艺北大核心CSCD

利用感应加热系统对激光沉积修复试样进行去应力退火局部热处理,研究了局部热处理的保温温度和时间对试样温度分布和残余应力的影响规律。结果表明:感应加热系统的局部加热效果明显;随着局部热处理保温温度的提高和保温时间的延长,加热区温度分布更加均匀;600℃去应力退火热处理后,残余应力平均降低30.6%以上,高于500℃去应力退火热处理后的应力消减幅度,局部热处理后由残余应力引起的端部变形量由2.67 mm消减为0.54 mm。试验验证了基于感应加热的局部热处理可有效消减修复应力和变形量。     

激光沉积修复金属去应力退火局部热处理工艺

利用感应加热系统对激光沉积修复试样进行去应力退火局部热处理,研究了局部热处理的保温温度和时间对试样温度分布和残余应力的影响规律。结果表明:感应加热系统的局部加热效果明显;随着局部热处理保温温度的提高和保温时间的延长,加热区温度分布更加均匀;600℃去应力退火热处理后,残余应力平均降低30.6%以上,高于500℃去应力退火热处理后的应力消减幅度,局部热处理后由残余应力引起的端部变形量由2.67 mm消减为0.54 mm。试验验证了基于感应加热的局部热处理可有效消减修复应力和变形量。     

热处理对变形AZ80镁合金组织和硬度的影响

研究了变形AZ80镁合金在不同热处理条件下组织和硬度变化。结果表明:镁合金在150~250℃退火时,晶粒先增大后减小,最终晶粒细小且均匀;但保温时间较长,退火温度为300~350℃时,晶粒尺寸比较稳定;在400℃退火处理后,短时间内晶粒立即出现异常长大现象,晶粒粗大且不均匀,合金性能较差。退火处理的最佳温度为280~350℃。热处理温度对AZ80镁合金的硬度值有显著影响,但退火处理时间的影响却不明显。     

退火热处理对高速电弧喷涂碳钢涂层组织性能的影响

采用高速电弧喷涂技术制备高碳钢涂层,并分别进行450、550和650℃保温2h的退火热处理,研究退火工艺对涂层的组织结构、相成分、残余应力及硬度的影响规律。结果表明,除了氧化物之外,高碳钢涂层在热处理前主要含有马氏体组织,450℃退火后出现了粒状渗碳体+铁素体特征的组织,550和650℃退火之后呈现块状特征的组织,且明显粗大;退火处理后涂层中的拉应力有减小的趋势;涂层硬度随着加热温度的升高而降低。因此,合适的热处理工艺可以有效地控制碳钢喷涂层的组织性能。     

焊后热处理对L245NCS微合金钢焊接残余应力的影响

采用履带式电加热法对L245NCS微合金钢焊接接头进行了不同退火温度和不同保温时间的焊后热处理,采用小孔法测量焊接残余应力。结果表明,560℃退火保温3.0 h焊后热处理方案和620℃退火保温1.5 h焊后热处理方案对降低焊接残余应力均较明显,其中560℃×3.0 h焊后热处理消除残余应力的松弛率在50%左右,620℃×1.5 h焊后热处理方案消除残余应力的松弛率基本高于80%,说明延长保温时间并不能有效地降低焊接残余应力。620℃×1.5 h焊后热处理方案对于消除L245NCS微合金钢焊接残余应力更为有效。     

Ti-Ni-V形状记忆合金超弹性研究

采用拉伸和应力-应变循环实验研究了退火温度、时效温度、时效时间、形变温度和应力-应变循环对Ti-50.8Ni-0.5V(原子分数,%)形状记忆合金超弹性(SE)的影响。随退火温度的升高,合金的应力诱发马氏体临界应力(σM)先减小后增大,超弹性残留应变(εR)先增大后减小再增大,为了获得优异的室温SE,退火温度应取500~600℃。随时效温度的升高,合金的σM降低,εR增加,SE变差;随时效时间延长,300℃时效态合金的SE稳定,400和500℃时效态合金的SE变差。随形变温度的升高,σM增加,SE改善。随循环次数增加,400℃退火态合金的SE稳定;500℃退火态合金的σM降低;600℃退火态合金的SE由非线性向线性转变。     

去应力退火对Ti40合金力学性能的影响

Ti40合金常规热处理后进行不同温度的去应力退火,观察并测试合金在不同去应力退火后的组织和力学性能。结果表明,不同的去应力工艺对材料的力学性能有较大的影响。当去应力温度在500℃到550℃之间时,Ti40合金室温、高温力学性能的强塑性匹配达到最好,此时持久性能虽有所降低,但能满足使用要求;而当去应力温度达到600℃以上时,合金的强度变化不大但是塑性急剧下降。推荐550℃×4 h为合金常规热处理后的最优退火工艺。     

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。