Cu-Al-Mn-Zn-Zr记忆合金的应力诱发马氏体相变及其逆转变

利用拉伸实验、电阻－温度曲线测量、X射线衍射、金相与透射电镜观察等方法研究了Cu-18.4Al-8.7Mn-3.4Zn-0.1Zr(原子分数，％）合金应力诱发马氏体的稳定性与可逆性。结果表明，顺Ms以上变形，实验合金发生应力诱发β1→M18R转变，但应力诱发马氏体转变很难进行完全。当变形量高达7．5％时，仍存在未发生应力诱发转变的母相。应力诱发马氏体的稳定性和可逆性与变形量大小有关，合金经大变形量变形后，即使在250℃油浴中回复，仍存在未发生逆变的应力诱发马氏体。在一定的变形条件下，经适量变形的应力诱发马氏体具有很高的可逆性和稳定性，实验合金在Ms以上10－50℃温度范围内变形6．5％－9．0％时，相变滞后宽度可达90℃以上，记忆应变＞3．5％。     

WC—Co硬质合金的高温拉伸塑性

在1150℃和1250℃之间的温库下研究了WC—Co硬质合金的高温拉伸变形。该变形应力对温度、应变速度、粘结相的体积百分数和其它碳化物添加剂是敏感的。应力—应变速率的相互关系，正如在超塑性金属中那样，在每个温度下分成三个区域。在温度1200℃下．在WC—6Co和WC—13Co(wt％)的合金中首次获得了大于100％的高延伸率。与超塑性金属相反，其最大的延伸率在区域Ⅱ中不能得到，而在区域Ⅰ和Ⅱ的边界上。破坏模式从区域Ⅰ的颈缩变成为区域Ⅱ的急剧断裂。     

Ni—Ti—Nb宽滞后形状记忆合金的形变诱发马氏体相变及其可逆性

用透射电镜、高分辨电镜、不同温度下的拉伸试验以及电阻率－温度曲线测试研究了Ｎｉ－Ｔｉ－Ｎｂ合金形变诱发马氏体相变及其可逆性，分析了形变诱发马氏体的稳定性和可逆性与其变体界面结构之间的关系。结果表明，Ｎｉ－Ｔｉ－Ｎｂ合金在Ｍｓ－Ｍｓ＾σ温度区间加应力时发生应力诱发马氏体相变，而在Ｍｓ＾σ以上温度加应力时，发生应变诱发马氏体相变。形变对Ｎｉ－Ｔｉ－Ｎｂ合金的应力诱发马氏体界面结构有明显影响，随着拉伸变     

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。     

温度和应变速率对Ti－1023合金等温压缩行为的影响

在(α+β)两相区对Ti-1023合金进行等温压缩试验,实测高温流动应力曲线,讨论流动应力及显微组织随温度及应变速率的变化规律,实验结果表明,Ti-1023合金的流动应力对应变速率非常敏感;变形温度对流动应力的影响程度与应变速率大小有关,在ε=1.0s-1的较快速变形时,当温度由760℃提高到800℃时,流动应力值下降约40MPa,而在ε=1.6×10-4s-1的慢速变形时,流动应力值仅下降10MPa;显微组织观察结果表明,在相同温度下较快速变形时(ε=1.0s-1),所得显微组织比较细小、均匀,而慢速变形时(ε=1.6×10-4s-1),初生α相及组织比较粗大,亚β晶界也比较明显。因此,在保证锻件良好成形的前提下,Ti-1023合金在等温锻造时可采用适当大的应变速率。     

CuAlMnZnZr合金拉伸变形及其宽滞后效应

利用拉伸试验、电阻—温度曲线测量、光镜、Ｘ射线衍射及透射电镜分析方法研究了Ｃｕ－Ａｌ１０．２－Ｍｎ４．９－Ｚｎ４．６－Ｚｒ０．３合金的宽滞后效应。结果表明，随着应变的增大，该合金相变滞后增宽，马氏体可逆转变量减少。在应力下合金组织变化如β→２Ｈ转变、１８Ｒ→２Ｈ转变、某些变体择尤长大，变体间的合并是主要变形机制。这些运动导致了交叉组织、带状组织、锯齿状边界、孪晶碎片及位错缠结的产生，破坏了变体间界面共格关系，使得其在热激活作用下难以运动。这可能是产生宽滞后效应和使可逆马氏体量减少的主要原因。     

Mg-5.6Zn-0.7Zr-0.8Nd合金高温塑性变形的热/力模拟研究

采用Gleebe-1500热／力模拟机研究了Mg-5．6Zn-0．7Zr-0．8Nd合金在应变速率为0．1，0．01和0．002s^-^3、变形温度为373—673K,最大变形程度60％条件下的高温塑性变形行为．分析了合金流变应力与应变速率、变形温度之间的关系，计算了高温变形时变形激活能和应力指数，并观察了合金变形过程中显微组织变化情况．结果表明：Mg-5．6Zn-0．7Zr-0．8Nd合金在热变形过程中不同温度下流变应力呈现不同形式，分析可知加工硬化、动态回复和动态再结晶在不同温度和不同应变速率下各自起到了重要的作用，合金变形激活能随应变速率增加而升高．在473K温度以上变形，合金发生明显动态再结晶且动态再结晶晶粒非常细小，晶粒尺寸为5—10μm，从而可明显提高合金的塑性．     

热变形TA15钛合金的显微组织和室温力学性能

通过等温恒应变速率压缩实验和X射线衍射、电子背散射衍射和透射电镜,研究了β区加热后在不同的变形温度和变形速率下变形水冷后TA15钛合金的微观组织;通过室温拉伸试验,对其抗拉强度和延伸率等性能进行了测试。结果表明,在α+β两相区压缩变形时,β转变组织中α相产生球化;水冷后发生β→α'马氏体相变。合金由球化α相、片状次生α相和针状马氏体α'相组成。在β相区压缩变形水冷后,合金主要为针状马氏体α'相。在相变点之上或之下的温度区间,随着变形温度的升高,合金的抗拉强度降低,延伸率增加;在相变点附近的温度过渡区间,随着变形温度的升高,合金的抗拉强度略有升高,延伸率降低。在相变点附近的两相区变形能获得较好的室温强塑性匹配。     

Ti49.4Ni50.6超弹性弹簧的相变和形变特性

用示差扫描量热仪、拉伸实验和应力-应变循环实验系统研究了退火温度、变形温度以及热循环和室温应力-应变循环对Ti49．4Ni50．6超弹性(SE)弹簧的相变和形变特性的影响。冷加工加中温退火态Ti49．4Ni50．6合金冷却→←加热时的相变类型为母相B2→←R相→←马氏体B19′。随退火温度升高，马氏体转变温度升高，R相转变温度降低。623-773K退火态Ti49．4Ni50．6弹簧室温下可获得SE特性，随变形温度升高，SE弹簧剐度增加；当退火温度超过823K后，SE持性变差。热循环时SE弹簧的切变量取值越小，其应变恢复率越高。预循环训练可增强SE的稳定性。     

热变形对35CrMo钢淬火马氏体晶体学特征的影响北大核心CSCD

通过热压缩实验获得不同应变下35CrMo钢的淬火马氏体组织。基于电子背散射衍射(EBSD)测试技术研究了热变形对35CrMo钢淬火马氏体晶体学特征的影响,重点分析了不同变形量下奥氏体晶粒尺寸及马氏体变体组合特征的变化。研究结果表明:多轮动态再结晶的出现造成了高温真应力-真应变曲线的多峰变化,且第1轮动态再结晶明显细化了奥氏体晶粒。原始奥氏体的晶粒取向决定了淬火后马氏体变体的类型,且淬火马氏体变体的组合方式均为密排面组合。不同变形量下淬火马氏体变体间的取向差集中在50°~60°范围内,可通过引入大角度晶界来细化晶粒。     

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.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.