Fe—Mn—Si合金的磁转变

利用电阻测量、Ｘ射线衍射等方法研究了铁锰基形状记忆合金中γ→ε相变与顺磁－反铁磁转变。对顺磁－反铁磁转变的温度区间和可逆性作了仔细分析。降温时→ε转为与顺磁到反铁磁转变的温度区间有重叠，但升温时反铁磁到顺磁的转变出现在－１４０℃到＋５０℃之间，ε→γ在１００－２００℃之间进行，二者截然分开     

亚稳奥氏体型Fe—Cr—Mn（W,V）合金的组织稳定性研究

通过对形变奥氏体组织进行长期时效观察合金相演化过程，研究了低放射性亚稳奥氏体Ｆｅ－Ｃｒ－ｎ（Ｗ，Ｖ）合金的组织稳定性。实验表明：合金在高于４００℃时，相平衡处在γ＋α＋α三相区，低于４００℃可以保证亚稳奥氏体的稳定性。亚稳奥氏体可以发生γ→α→α转变也可以发生γ→γ（ｆ）→＇（ｆ）→α转变，ε马氏体不是γ→α转变的唯一中间过渡相。形变诱发ε马氏体形成过程中伴随奥氏体晶粒碎化，可产生细晶强化作用，这     

Fe—Mn—Si合金在Neel温度以下的γ→ε相变

用电阻法、磁化率和Ｘ－光衍射等方法研究了Ｆｅ－３０Ｍｎ－６Ｓｉ形状记忆合金在Ｎｅｅｌ温度以下的γ→ε相变,与以前工作不同,本文实验结果显示,在某些Ｆｅ－Ｍｎ和Ｆｅ－Ｍｎ－Ｓｉ合金中磁转变并不阻止ε马氏体相在Ｎｅｅｌ温度以下的和成。     

γ-Fe-Mn-Al-Cr合金的顺磁-反铁磁性转变

研究了γ-Fe-Mn-Al-Cr(Mnl8.6—25.6,A10—9.8,CrO—5.7at.-%)合金中磁化率x,弹性模量E及电阻率p与温度T的关系.实验结果揭示该合金中存在顺磁-反铁磁性转变.提高Mn含量将降低合金的x和升高反铁磁转变温度T_N.相反,随着Al含量的增加,x增大,T_点降低,X-T曲线在T_N点的峰值增高;T>T_N时,|dx/dT|增大.Cr对Fe-Mn合金x-T曲线的影响较小,T>T_N时,X几乎不因T而变化.合金中γ→ε马氏体转变引起X降低,反之,ε→γ转变导致x升高.以多元回归分析建立γ-Fe-Mn-Al-Cr合金中T_N点与成分的经验关系.在顺磁-反铁磁性转变温度附近伴有E及ρ的反常变化,呈现“电阻率极小”.现在对Fe-Mn-Al合金的ρ反常还难以作出确切的解释,负电阻温度系数的产生可能与形成反铁磁能隙有关.所得结果对发展Fe-Mn-Al-Cr系反铁磁Invar合金及超低温无磁钢有一定的参考价值.     

奥氏体型Fe—Cr—Mn（M,V）合金相稳定性研究

通过形变加工和长期时效热处理，研究了（Ｃ＋Ｎ）复合强化的Ｆｅ－１３Ｃｒ－１７Ｍｎ（Ｍ，Ｖ）奥氏体合金的稳定性和相平衡特点，结果表明：在５００℃以下合金奥氏体稳定，不发生γ→α转变。采用（Ｃ＋Ｎ）复合添加晶粒细化，可有效抑制ε马氏体形成和σ相析出。５００～７００℃长期时效后形变诱发大量碳化物析出，Ｍｓ点提高，加快形变诱发α马氏体分解和再结晶，促使γ→α转变和σ相析出，合金奥氏体变得不稳定。     

Fe－Nb－C合金的高温内耗

测量了高纯Ｆｅ－Ｎｂ－Ｃ合金的４００－８５０℃内耗，发现一个峰温度随测量应变振幅变化的高温（６６６－７４０℃）磁机械滞后阻尼内耗峰。研究了峰的特征、出现、消失条件及升降温、频率、振幅、变形与退火等因素对峰的影响．提出了用内耗实验确定材料中阻碍铁磁畴壁Ｂａｒｋｈａｕｓｅｎ跳动应力的方法和合金中产生磁机械滞后阻尼－温度峰（Ｑ_ｍ~（－１）－Ｔ）的物理机制。     

用ODF理论研究Fe－30Ni合金α－γ_r逆相变过程的织构变化

研究了Ｆｅ－３０Ｎｉ合金冷轧板由马氏体到奥氏体（α－γ_ｒ）逆相变过程中的织构变化．原始材料的组织状态为形变马氏体、淬火马氏体及残余奥氏体．经过在不同温度加热后,利用Ｘ射线衍射精确测量了马氏体及奥氏体的取向密度分布函数（ＯｒｉｅｎｔａｔｉｏｎＤｉｓｔｒｉｂｕｔｉｏｎＦｕｎｃｔｉｏｎ简称ＯＤＦ）．结果表明,逆相变过程中奥氏体的织构变化可分为两个阶段：低温区,奥氏体织构逆变为原冷轧奥氏体织构,相变的进行可解释为具有强烈取向选择的剪切机制;高温区,相变的进行为定向长大机制,逆变奥氏体织构与冷轧奥氏体织构之间出现偏差,｛２１１｝〈１１１〉织构成分比原冷轧织构强度变弱．由ＯＤＦ差得到两温度区间的相变停止温度,此温度与取向有关,并可假设为相变机制变化温度．相变停止温度越高的取向,以定向长大机制进行的相变开始得越晚．     

10Cr14Ni6Mn4不锈钢的马氏体转变

用光学显微镜、透射电子显微镜和Ｘ射线衍射仪研究了经１０５０℃×０．５ｈ固溶处理和６９．１％冷变形，再快速加热到８００℃～１１００℃水冷后，放入液氮中冷处理的１０Ｃｒ１４Ｎｉ６Ｍｎ４钢的马氏体转变。试验结果表明，试验用钢存在γ→ε、γ→ε→α和γ→α３种形式的马氏体转变。ε马氏体的形态为细片状，ε马氏体和奥氏体的位向关系为（１１１）γ∥（０００１）ε、［１１２］γ∥［１２１０］ε。α马氏体有两种形态：板条状马氏体和细颗粒状马氏体。α马氏体和奥氏体的位向关系符合Ｋ－Ｓ关系。     

含Al,Si反铁磁性γ-Fe-Mn基合金中的电阻极小

本文研究Al,Si及Cr对反铁磁性γ-Fe-Mn基合金的Neel转变及电阻极小的影响.结果表明,Cr对Fe-Mn基合金的磁化率(X),X-T及ρ(电阻率)-T关系的影响较小,也不促进基体形成局域净磁矩.相反,Al,Si则显著改变γ-Fe-Mn合金的磁结构、X-T及ρ-T关系,在Neel温度T_N以下,随反铁磁转变的磁性电阻ρ_m的增大,出现电阻极小,随后出现负电阻温度系数.降温直至4.3k,γ-Fe-Mn及γ-Fe-Mn-Cr合金在试验精度内未呈现任何电阻反常变化,而固溶Al或Si后则观察到第二次电阻极小,电阻极小温度T_(min)~(2)与电阻极小深度△ρ(ρ_(4k)～ρ_(T_(min)))随Al,Si浓度的增大而增加,且在T_(min)~(2)—4k间,ρ随lgT的降低而线性增大.由此可以假定,反铁磁态γ-Fe-Mn中加入Al或Si,导致Fe离子处形成局域净磁矩,并发生ISDW-CSDW态转变,因而产生类似Kondo效应的低温电阻极小.     

RESISTIVITY MINIMUM IN ANTIFERROMAGNETIC γ-Fe-Mn BASE ALLOYS CONTAINING Al OR Si

本文研究Al,Si及Cr对反铁磁性γ-Fe-Mn基合金的Neel转变及电阻极小的影响.结果表明,Cr对Fe-Mn基合金的磁化率(X),X-T及ρ(电阻率)-T关系的影响较小,也不促进基体形成局域净磁矩.相反,Al,Si则显著改变γ-Fe-Mn合金的磁结构、X-T及ρ-T关系,在Neel温度T_N以下,随反铁磁转变的磁性电阻ρ_m的增大,出现电阻极小,随后出现负电阻温度系数.降温直至4.3k,γ-Fe-Mn及γ-Fe-Mn-Cr合金在试验精度内未呈现任何电阻反常变化,而固溶Al或Si后则观察到第二次电阻极小,电阻极小温度T_(min)~(2)与电阻极小深度△ρ(ρ_(4k)～ρ_(T_(min)))随Al,Si浓度的增大而增加,且在T_(min)~(2)—4k间,ρ随lgT的降低而线性增大.由此可以假定,反铁磁态γ-Fe-Mn中加入Al或Si,导致Fe离子处形成局域净磁矩,并发生ISDW-CSDW态转变,因而产生类似Kondo效应的低温电阻极小.     

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。