Ti-55531钛合金β相区热变形行为及本构方程的研究

为了提高Ti-55531钛合金β相区锻造的损伤容限,通过Gleeble-3800热模拟试验机对Ti-55531合金在β相区进行了应变速率为0.001～1s-1,温度为860～950℃的等温压缩试验,获得了流动应力曲线。对Ti-55531合金在试验条件下热变形行为及流动应力变化进行了研究。结果表明,Ti-55531合金的流动应力曲线为稳态流动型,在相同的应变速率下,变形温度越低,流动应力越大;在相同的温度下,应变速率越快,流动应力越大。通过对试验数据拟合得到了0～0.7应变量的Ti-55531合金本构方程。方程的准确度高,平均误差为8.99%。在试验条件下,平均热激活能为209.204 kJ/mol,最小值为200.389 kJ/mol。     

Ti-575钛合金热变形行为及微观组织演变

本文以Ti-575钛合金为研究对象，分别对魏氏组织和双态组织Ti-575钛合金进行热模拟压缩实验，分析不同热变形条件下的真应力-应变曲线，构建了其在α+β相区的热变形本构方程，并分别探究了变形温度和应变速率对微观组织的影响。结果表明，流变应力值随着变形温度的升高而降低，随着应变速率的升高而升高；当应变速率为0.1 s-1及以上时，随着变形温度的升高流变曲线出现了不连续屈服现象。根据两种组织Ti-575钛合金流变曲线的峰值应力，分别计算出其在α+β相区的变形激活能，构建Arrhenius型热变形本构方程。在不同的热变形条件下，随着变形温度的升高，魏氏组织Ti-575钛合金动态再结晶的程度越来越大，而双态组织Ti-575钛合金等轴αp相体积分数和尺寸逐渐降低；随着应变速率的降低，魏氏组织Ti-575钛合金动态再结晶的程度逐渐增大，而双态组织Ti-575钛合金等轴αp相体积分数先减少后增加；双态组织Ti-575钛合金在830℃或1 s-1应变速率下热压缩时，显微组织中残留少量的粗片层α相没有发生相变，βt基体中会有硅化物析出。     

Hot Deformation Behavior of TB8 Alloy near the β-Transus

通过热模拟压缩试验,对TB8钛合金β相变点附近的高温变形行为进行了研究.热模拟压缩试验的变形温度为650～900℃,应变速率为0.01～10 s-1.通过试验分别得到了TB8钛合金双相区(α+β)和单相区(β)的流变应力曲线,并分别研究了流变应力与变形温度、应变速率和微观组织演化的关系.在10 s-1的高应变速率下,真应力-真应变曲线在850和900℃出现了双峰,这一现象未见报道.通过本构关系推导,得到了TB8钛合金双相区(α+β)和单相区(β)的表观激活能分别为233.0151和197.8987 kJ/mol.另外,建立了TB8钛合金双相区(α+β)和单相区(β)相应的流变应力本构方程.     

Ti-5Al-5Mo-5V-3Cr-1Zr合金β相区热变形行为及位错密度内变量本构模型

通过热压缩模拟试验机Gleeble3500进行了Ti-5Al-5Mo-5V-3Cr-1Zr(Ti-55531)合金在β相区的热模拟压缩试验(变形温度为860、885、910、935℃,应变速率为0.001、0.01、0.1、1 s~(-1)),采用光学显微镜分析了材料的组织演化行为。结果发现,Ti-55531合金变形过程中的动态软化效应以动态回复为主,在低应变速率下,组织呈现再结晶特征。为了通过材料变形机制去描述流动应力行为,考虑加工硬化和动态软化机制对位错密度的影响,建立了Ti-55531合金在β相区的位错密度内变量本构模型。结果表明,该模型能够准确预测Ti-55531合金在β相区的热变形行为。     

Ti6Al4V2Cr1.5Mo0.5Y钛合金热变形行为

对退火后Ti6Al4V2Cr1.5Mo0.5Y钛合金在不同温度1223~1332 K和不同应变速率0.01~1.0 s~(-1)条件下压缩实验的热变形行为进行研究,绘制应力-应变曲线,及温度、速率、应力等参数之间的关系图,求解激活能,建立该合金的本构方程。结果表明:应变速率一定时,流变应力随温度的升高而降低;变形温度一定时流变应力随应变速率的增大而升高;合金的热激活能为286.1655 k J/mol。     

Beta C钛合金在β相区的热变形行为及组织演化（英文）

利用Gleeble-3800热模拟试验机对beta C钛合金进行等温压缩试验,研究其在β相区的热变形行为。得到了描述热变形行为的本构方程,获得了真应变为0.7时的加工图。采用光学显微镜、扫描电子显微镜和电子背散射技术对变形显微组织进行表征。结果表明:流变应力随着应变速率加快而增大,随着试验温度的升高而减小。计算得到的表观激活能为167 k J/mol,接近β钛的自扩散激活能。加工图和显微组织观察表明在温度为900~1000°C和变形速率为0.1~1 s~(-1)的区间存在一个动态再结晶区。加工图显示,当变形速率大于1.7 s~(-1)时,beta C钛合金发生不稳定变形。Beta C钛合金在动态再结晶区变形后,经合适的热处理,显微组织可以被优化。     

5005铝合金热压缩变形行为

采用Gleeble-3500热模拟试验机对5005铝合金材料进行热压缩试验,应变速率为0.01~10 s~(-1),变形温度为300~500℃,研究了材料的流动应力,并建立了本构方程。研究结果表明:在本实验中,5005铝合金具有负温度敏感性和正应变速率敏感性。变形初期,流动应力随变形程度的增加而迅速升高,达到峰值后,逐渐趋于平缓,此时流变曲线表现为稳态流变特征;该铝合金的热压缩流动应力可用包含Zener-Hollomon参数的双曲正弦关系来描述,其热变形激活能Q为180.69 k J·mol~(-1)。     

Fe-Si合金高温变形流变应力的本构模型

在热模拟机上通过单道次压缩试验,研究了铁素体单相和含有少量奥氏体的两种Fe-3%Si钢的高温变形行为,并建立了试验钢的高温本构关系模型。结果表明,变形温度900~1100℃、应变速率0.05~2 s~(-1),变形量0.8或1.0条件下,Fe-3%Si钢应力应变曲线均为典型的动态回复型,回复速率较快,稳态或峰值应力约30~80 MPa,可见连续动态再结晶现象。单相和双相试验钢的变形激活能分别为298 k J/mol和272 k J/mol,本文建立的高温流变模型具有较高的精度,计算得到的峰值应力、真应力-应变曲线与试验结果吻合良好。     

Ti-46.5Al-2.5V-1.0Cr-0.3Ni合金高温锻造本构模型研究

采用Gleeble-1500热模拟试验机对Ti-46.5Al-2.5V-1.0Cr-0.3Ni合金进行了温度1000～1200℃、应变速率0.001～1.0 s-1的等温热压缩实验,根据摩擦修正后的流变应力曲线,研究了工艺参数变化对流变应力的影响,建立了TiAl合金高温变形的本构模型.结果表明:流变应力随变形温度升高而降低,随应变速率提高而增大,并且通过线性回归分析获得了1000～1200℃时的变形激活能为466 kJ·mol-1和高温锻造本构方程.     

新型T91稀土钢的高温塑性变形及动态再结晶行为

为研究新型T91稀土钢的热力学性能,采用Gleeble-1500D热模拟试验机测定变形温度θ为1100~1250℃、ε觶为0.5~5 s-1时的应力-应变曲线,并采用Zener-Hollomon参数法构建该钢不同条件下高温塑性变形的本构方程。结果表明:在高变形温度及低应变速率时,测定的T91稀土钢应力-应变曲线呈双峰特征,有动态再结晶现象产生。随变形温度升高及应变速率的降低,动态再结晶现象越易发生;应变速率越小,流变应力下降越明显。T91钢的热变形激活能为509.04k J·mol-1。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.