低相变温度宽相变滞后的Cu-Al-Mn-Nb形状记忆合金

通过恰当的成分设计,获得了具有较低马氏体相变温度及较宽相变滞后的Cu-Al-Mn-Nb形状记忆合金.用差热分析法(DSC)测得Cu-26.8Al-4.8Mn-1.0Nb(摩尔分数,%)合金在降温时马氏体相变最激烈的温度为-32℃;升温时奥氏体相变最激烈时的温度为68℃;相变滞后宽度达100℃.透射电镜、扫描电镜及X射线衍射分析表明,该合金的马氏体为2H型结构,宽滞后效应是由于合金进行马氏体相变时析出了点状富铌颗粒从而松驰掉一部分弹性应变能而产生的.该合金在表面应变为4%时,弯曲变形试样的形状回复率达93%以上,在室温下时效2个月后,其形状回复率没有发生明显恶化.室温下其抗拉强度约为550 MPa,屈服强度约为380 MPa,塑性延伸率约为7%.     

固溶温度对CuZnAl合金形状记忆性能的影响

研究了Cu-26．87Zn-3．85Al(wt％)形状记忆合金固溶温度对其形状回复率的影响。结果表明，该合金采用固溶 上淬工艺处理后，在600℃～720℃范围内，形状回复率随着固溶温度的升高迅速增加，在720℃后趋于稳定，达到最大值；固溶温度越高，合金晶粒越大，会对其力学性能造成负面影响，在能保证合金形状记忆性能的基础上应尽量保证合金的晶粒小，因此其最佳固溶温度是720℃。将该合金在室温下自然时效一个月后，由于马氏体稳定化，其形状回复率有小幅度下降。     

EFFECT OF AGING ON THERMOELASTIC MARTENSITE TRANSFORMATION IN Cu-Zn-Al ALLOY

本文用直流电阻法研究了时效对M_s点高于室温的工业纯Cu—Zn—Al合金热弹性马氏体转变的影响。若该合金从高温无序β相区淬火后立即在马氏体状态充分时效,则热弹性马氏体会发生稳定化,在升降温的电阻—温度曲线上,马氏体不再呈现热弹性正逆转变的特征;若该合金淬火后立即在β_1状态(母相状态)时效,则随着β_1状态时效时间的延长,合金马氏体的热弹性转变特性会逐步保持下来,其马氏体相变点和马氏体相对可逆转变量逐渐趋近一稳定值,在随后的热循环中它们变化很小.可以认为,马氏体态时效所引起马氏体的稳定化与马氏体的再有序化及过饱和空位的聚集等过程有关。     

时效对Cu-Zn-Al合金热弹性马氏体转变的影响

本文用直流电阻法研究了时效对M_s点高于室温的工业纯Cu—Zn—Al合金热弹性马氏体转变的影响。若该合金从高温无序β相区淬火后立即在马氏体状态充分时效,则热弹性马氏体会发生稳定化,在升降温的电阻—温度曲线上,马氏体不再呈现热弹性正逆转变的特征;若该合金淬火后立即在β_1状态(母相状态)时效,则随着β_1状态时效时间的延长,合金马氏体的热弹性转变特性会逐步保持下来,其马氏体相变点和马氏体相对可逆转变量逐渐趋近一稳定值,在随后的热循环中它们变化很小.可以认为,马氏体态时效所引起马氏体的稳定化与马氏体的再有序化及过饱和空位的聚集等过程有关。     

生物医用Ti-16Nb-4Sn合金的超弹性和形状记忆效应

通过室温下拉伸及弯曲试验,研究了淬火温度以及循环拉伸对Ti-16Nb-4Sn(at%)合金的超弹性和形状记忆效应的影响.发现锻造态合金在室温变形后具有接近完全的超弹性.700℃冰水淬火的合金具有最好的形状记忆效应,室温变形后在150℃加热,形状回复率可达21.1%,但超弹性却最低.超弹性和形状记忆效应具有互补性.循环拉伸可以明显改善合金的超弹性.对于锻造态和经400℃冰水淬火的合金,通过4%应变量循环拉伸3次后均可获得完全的超弹性.XRD分析结果表明,室温下合金的组织为β α"马氏体.     

淬火对Fe—Mn—Si—Cr—Ni记忆合金回复率的影响

研究淬火加热温度对（Ｗ％）Ｆｅ－１４．９Ｍｎ－６．３Ｓｉ－８．８Ｃｒ－５．２Ｎｉ形状记忆合金形状回复率的影响。试验结果表明，形状回复率随淬火加热温度升高而提高，７００℃￣８００℃淬火，达到最大值，随后回复率随淬火加热温度进一步升高而降低。淬火加热温度越高，热诱发ε马氏体数量越多。热诱发ε马氏体对形状记忆效应具有双重作用。适量的热诱发ε马氏体有利于提高形状回复率。     

Fe-Mn-Si形状记忆合金应力诱发马氏体相变的X射线分析

采用X射线衍射法对Fe-17Mn-5Si-10Cr-5Ni和Fe-17Mn-5Si-2Cr-2Ni-1V合金的应力诱发马氏体相变进行了定量的分析。研究结果表明，Fe-17Mn-5Si-10Cr-4Ni合金试样在室温下拉伸，当变形量约为6％时，应力诱发ε马氏体的体积分数达最大值约64％；在预变形量超过5％时，α‘马氏体即开始出现且增加迅速；揭示在大变形下，Fe-Mn-Si合金中发生了应力诱发γ→ε→α‘马氏体相变。Fe-17Mn-5Si-2Cr-2Ni-1V合金试样在室温拉伸时应力诱发ε马氏体量较Fe-17Mn-5Si-10Cr-4Ni合金更多，即使在预变形量超过10％时，也不出现α‘马氏体。预变形温度降低，可促进应力诱发马氏体相变。     

淬火温度对Co40.5Ni34Al25.5合金相变和磁性的影响

用金相显微分析、DSC和VSM方法研究了Co40.5Ni34Al25.5合金马氏体相变和Curie点随淬火温度的变化,通过三点弯曲试验研究其形状记忆效果.结果发现该合金马氏体相变温度和Curie点与淬火温度成正比关系.马氏体相变的4种温度,即Ms,Mf,As和Af基本平行变化,淬火温度每升高10℃,马氏体相变温度和Curie点升高8℃～9℃.β相中Al的含量随淬火温度升高而降低,因而使马氏体相变温度和Curie点升高.1320℃淬火的Co40.5Ni34Al25.5合金的弯曲强度约为450 MPa,弯曲试验表明Co40.5Ni34Al25.5合金有双向形状记忆特性.     

母相时效对Cu-17Al-10Mn合金相变温度和形状记忆性能的影响

研究母相时效过程中Cu-17Al-10Mn(摩尔分数,%)形状记忆合金马氏体转变温度Ms和形状记忆性能的变化规律.结果表明:合金淬火态的Ms比室温的低,室温时合金为无序母相结构,低温时可转变为马氏体;随着时效温度的提高,Cu-17Al-10Mn合金的Ms和形状恢复率均逐渐升高,并在150 ℃时效15 min后达到最大值,这主要归因于淬火空位的逸出使其对母相的钉扎作用减弱;随着时效温度的进一步提高,由于母相分解为贝氏体,合金的Ms和形状恢复率都下降,在250 ℃时效15 min后,母相完全分解,合金的形状恢复率降低到零.     

奥氏体预变形温度对提高Fe－Mn－Si合金记忆效应的影响

本文研究了５７３─１０７３Ｋ温度范围内３％奥氏体预变形对Ｆｅ－２９．９％Ｍｎ－６．０％Ｓｉ合金记忆效应的影响．结果表明，固溶态的样品经奥氏体预变形后，在室温变形时，记忆应变（ε（ｔｒ））、应变回复率（η）及记忆应变达到饱和所对应的应变值都得到了明显的提高：随预变形温度升高，室温经约２．５％变形后应变回复率增加，并在合金动态再结晶开始温度９７３Ｋ预变形后具有最大值９８％；经９７３Ｋ预变形，合金的最大记忆应变由固溶态的１．７％提高至３．８％，完全记忆应变达２．２％；奥氏体预变形的作用在于降低了室温诱发ε马氏体的临界应力．     

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。