含Nb微合金钢静态应变时效行为研究

采用扫描电镜、透射电镜及多功能内耗测量仪,研究了C-Mn型钢及含Nb微合金钢在应变时效过程中的微观组织结构变化以及内耗行为。结果表明:在应变时效过程中,宏观组织没有发生明显的变化,组织稳定;应变时效处理后,C-Mn型钢和含Nb微合金钢的硬度均提高,冲击韧度下降,韧脆转变温度升高;微合金元素Nb能有效地降低钢板的应变时效敏感性;两种钢板在250℃加热时均有冷加工内耗峰存在,这与游离态的碳原子钉扎位错和脱钉有关,而含Nb微合金钢在室温没有内耗峰存在。     

利用FR内耗峰对高锰奥氏体合金钢高温时效动力学过程的研究

采用内耗方法分析了高锰奥氏体合金钢在720℃时效不同时间MC型碳化物析出动力学过程。结果表明,随着时效时间增加,其在652 K左右出现的FR内耗峰强逐渐降低且峰宽变窄。证明了时效过程固溶于奥氏体间隙中的C发生了重新分配,碳化物不断析出导致基体合金含量降低。基于720℃时效不同时间FR内耗峰峰强变化,并结合JMA方程证明了在720℃时效过程中,间隙C原子与奥氏体基体中固溶合金原子形成的碳化物以缺陷为核心形核长大。基于内耗分析结果,通过理论计算分析奥氏体合金钢中碳化物(MC型)时效析出过程,可见通过FR峰峰强变化可分析高锰奥氏体合金钢中碳化物析出动力学。     

铌微合金钢析出相的形成与长大规律

将铌微合金钢在1200 ℃固溶2 h,然后分别在700 ℃时效5、15、30和60 min.利用显微硬度计和电阻仪,结合三维原子探针研究了铌微合金钢中析出相的萌生规律及其对硬度和电阻率的影响.结果表明,层片状的NbC团簇在700 ℃时效5 min时已经形成,团簇尺寸随着时效时间的延长而增大.当时效时间为30 min时,团簇数量密度达到最大值.在30 min前,细小碳化物使得显微硬度值上升、电阻率下降.而当时效时间超过30 min,碳化物以长大为主,碳化物粗化使得硬度值下降、电阻率上升.     

变形Fe-Nb-C合金的室温至180℃内耗

测量了700℃，30min水冷后变形Fe－Nb-C合金室温至180℃的内耗，发现除Snoek峰外，合金在此温度区还有阻尼峰。测量了合金经过980℃，2h中间处理样品的内耗，并给出变形及室温原位时效的汽车钢ST14与GBPH340的内耗结果。认为Fe-Nb-C合金的变形“B”峰。是被饱和Cotterll气团碳原子团簇钉扎的位错段拖曳碳的稀Cottrell气团运动引起的，是合金在变形时碳原子稀Cottrell气团择优分布在位错上的结果。     

热处理工艺对TB2钛合金组织和性能的影响

研究了不同热处理工艺对TB2钛合金板材显微组织和力学性能的影响。结果表明,该合金在730℃以上固溶处理已经开始再结晶,在730～820℃之间处理的样品强度和延伸率变化不大;在760℃固溶处理3min,再结晶已经开始,保温时间〉120min时晶粒变得相当粗大;合适的固溶处理制度为760℃,10min;在固溶处理制度相同,时效时间为2h,时效温度变化对强度和塑性影响大不;时效时间延长至8h,随时效温度升高,Rm,RPo2呈下降趋势;760℃,10min固溶处理加500℃,8h时效处理后,Rm,值最高可达到1360MPa。     

6022铝板热冲压淬火一体化工艺固溶条件对强化的影响

利用中心点响应面法进行铝板热冲压淬火一体化实验设计,通过常温单向拉伸实验、热像仪测温及扫描电镜金相观察,研究了固溶处理工艺参数及淬火冷却速率对成形件强度的影响。实验结果表明:固溶处理工艺参数即固溶温度、固溶时间的最优参数范围分别为520~545℃,35~45 min。在此条件下,经时效温度180℃,时效时间60 min的人工时效处理后成形件的抗拉强度最高可达到370 MPa。选取最优工艺参数范围中的固溶温度520℃,固溶时间35 min的工艺过程,进行淬火温度测量及成形件金相观察,发现通过室温条件下的模具淬火可以实现成形件的快速冷却,并且成形件经人工时效后可得到细小且弥散分布的强化相。     

Fe-23%Al合金固溶淬火过程调幅分解与有序化共存的内耗研究

利用内耗方法结合TEM、XRD研究了Fe-23%Al合金固溶淬火过程中调幅分解与有序化共存的研究,结果表明:固溶淬火态过程中α相分解成贫铝的α相和B2结构FeAl相,存在调幅分解和有序化共存的过程。固溶淬火态Fe-23%Al合金中在150和300℃左右出现2个显著的内耗峰,而这些内耗峰在退火试样中并没有发生;300℃内耗峰对应FeAl-VFe偶极子弛豫运动,150℃内耗峰对应双空位偶极子弛豫运动。2个内耗峰的出现证明在淬火过程中出现了调幅分解与有序化共存。     

热处理制度对Ti49.2Ni50.8合金内耗性能的影响

利用X射线衍射、扫描电镜和倒置低频扭摆仪研究了不同热处理状态Ti-50.8%Ni(摩尔分数)合金的低频阻尼性能.结果表明:固溶处理试样只存在马氏体相变内耗峰,而时效处理试样中既有马氏体相变内耗峰,也发现有R相变内耗峰,相变内耗峰均对应弹性模量极小值,相变内耗峰与频率成反比;在时效处理试样中,马氏体相和R相的阻尼性能高于母相(B2);时效处理对马氏体相变有抑制作用;在400℃时效的TiNi合金中,于200K左右处发现内耗峰,随着频率的增加,低温内耗峰向高温方向运动,此内耗峰与时效析出的Ti3Ni4粒子钉扎位错有关,用钉扎位错脱钉的G-L模型解释了低温内耗峰,此内耗峰的脱钉既包括机械脱钉,也包括热激活脱钉.     

固溶+时效处理对6A02铝合金组织与力学性能的影响

采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)及力学性能测试等手段,研究了固溶时效制度对6A02铝合金组织及力学性能的影响.结果表明:在520℃固溶温度下,保温45 min下6A02铝合金能达到固溶要求.合金的峰时效制度为160℃/14h,在峰时效状态下,第二相细小弥散,合金的抗拉强度达到360 MPa...     

内耗法研究退火温度对含钒BH钢中固溶C原子浓度的影响

采用内耗方法研究退火温度对含钒超低碳烘烤硬化钢间隙固溶C的影响。对试样进行不同温度盐浴退火处理后,通过内耗法测量Snoek峰来研究固溶C随退火温度的变化规律,并测量相应的BH值和晶粒尺寸变化规律。研究结果显示:含V超低碳烘烤硬化钢在750～810℃盐浴退火,随着退火温度的升高,Snoek峰先逐渐下降后略有升高,间隙固溶C含量亦先减小后增加;但随着退火温度的进一步提高,间隙固溶C的浓度增加,内耗峰又有所上升,此结果与BH值对比取得了较好的一致性。此外随着内耗测试频率的降低,内耗与固溶C含量的比例系数K也随之降低。     

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。