TA15钛合金热变形本构方程及热加工图

采用Gleeble-3800热模拟试验机对TA15钛合金进行了热压缩,获得了TA15钛合金在750~980℃、应变速率在0.001~1 s~(-1)的应力-应变曲线。基于TA15钛合金的压缩试验数据建立了高温热变形本构方程和热加工图,并结合热加工图分析了TA15钛合金热变形组织,确定了TA15钛合金的合理热加工参数范围。结果表明,TA15钛合金本构方程为双曲正弦函数,可由Z参数表示,其热变形激活能为523.374 k J/mol。TA15钛合金高温热变形最佳工艺参数为变形温度875~980℃和应变速率0.01~0.10 s~(-1)。     

TA11钛合金热变形本构方程

在Gleeble-3500热模拟试验机上进行等温热压缩试验,得到TA11钛合金在温度为954~1074℃、应变速率为0.05~5 s~(-1)、变形量为60%条件下的真应力-真应变曲线。根据真应力-真应变曲线,分析流变应力随变形温度、应变速率和应变的变化规律。结果表明,流变应力与变形速率成正比,与变形温度成反比;利用Arrhenius双曲正弦方程和Z参数建立了TA11钛合金的热变形本构方程。经验证明,试验值与所建立的本构方程的预测值吻合较好,可用于预测TA11钛合金塑性变形过程中的变形抗力和作为有限元数值模拟的材料模型。     

TA10钛合金多向锻造数值模拟本构方程的构建

本文为研究TA10钛合金组织形貌与力学性能的关系,通过热模拟试验,对TA10钛合金在800℃～1050℃变形温度范围内和不同应变速率下(0.01s~(-1),0.1s~(-1),1s~(-1)和5s~(-1))进行热变形研究。通过对真应力-真应变分曲线的分析,探索了相应的软化机制,确定了热变形激活能,建立了本构关系。研究了峰值应力与温度和变形速率之间的函数关系,为TA10钛合金的多向锻造加工控制提供理论基础。     

TA15钛合金高温热压缩变形行为及热加工图

获得准确的钛合金塑性变形特征和热加工条件,是钛合金挤压、轧制等塑性加工工艺参数选择的重要依据。本实验研究了TA15钛合金在应变速率0.01~20 s~(-1)、变形温度850~1050℃条件下的压缩变形行为、组织特征,采用Arrhenius双曲正弦函数模型推导出了TA15本构方程,基于动态材料模型建立了合金在真应变0.1~0.7时的热加工图。结果表明,在本实验的应变速率和变形温度的条件下进行压缩变形,随着变形温度的升高,合金中的α相逐渐向β相转变;随着应变速率的提高,α相向β相转变的程度逐渐减小。根据热加工图确定了合金的两个热加工安全区域:(1)变形温度950~1050℃、应变速率0.01~0.37 s~(-1);(2)变形温度875~950℃、应变速率1.65~13.5 s~(-1)。     

基于修正JC模型的TA12钛合金高温流变行为

为了研究TA12钛合金高温流变行为,构建能准确描述其高温流变行为的本构模型,对TA12钛合金进行了温度范围为700～850℃,应变速率为0.001～0.1 s~(-1)的高温拉伸试验。结果表明:在所研究的变形条件下,流变应力随应变的增加而逐渐增大,达到峰值应力后又逐渐减小,直至材料发生断裂,并在850℃、0.001 s~(-1)的变形条件下出现了稳态流动应力。综合考虑应变硬化效应、应变速率硬化效应和热软化效应的影响,提出一种修正的JC本构模型,可准确地描述TA12钛合金的高温流变行为。     

航空用TA15钛合金热变形行为研究

利用Gleeble-3800热模拟试验机,在温度800~980℃及应变速率0.001~1 s~(-1)范围内进行了TA15钛合金热压缩试验,研究了TA15钛合金在热变形过程中力学行为特点及微观组织演变规律。研究结果显示,变形温度和应变速率对流变应力影响显著。随着变形温度升高和应变速率的降低,最大变形抗力减小,且使得流变曲线在较小应变下即达到稳态。当变形温度低于或等于900℃时,随应变的增加合金的动态软化效应显著,当温度高于900℃时,合金的软化效应逐渐减弱,这主要与温度升高导致密排六方α相与体心立方β相两相比例改变进而导致主导软化机制改变有关。基于流变曲线,建立了考虑摩擦效应和应变补偿的热变形本构方程。对比分析表明所建立的双曲正弦型本构模型可较好地预测不同变形阶段合金流变应力,可为TA15钛合金热加工工艺的选择等提供参考依据。     

TA7钛合金高温变形行为研究（英文）

为了分析TA7钛合金的热变形工艺参数,通过高温压缩试验对TA7钛合金的高温变形行为进行了研究。试验温度为1123~1273K,应变速率为0.001~1 s~(-1)。此外,提出了一种修正并联本构模型用来分析应变速率、变形温度及应变对流动应力的影响。然后,基于动态模型,建立了TA7钛合金的热加工图,并通过微观组织分析对加工图的准确性进行了验证。结果表明,TA7钛合金合理的工艺参数为变形温度1223 K,应变速率0.001 s~(-1),而其非稳态区域位于低温高应变速率区。     

TC4钛合金流动软化行为及本构模型研究

利用Gleeble-3500热模拟试验机进行等温恒应变速率热压缩实验,研究了TC4钛合金在温度800~950℃、应变速率0.001~10 s~(-1)条件下的流动软化行为。研究发现随变形温度降低和应变速率增大TC4钛合金的流动软化程度增大,且800~850℃、应变速率1~10 s~(-1)变形时的流动软化主要是塑形流动失稳引起的,温度900~950℃、应变速率0.001~0.1 s~(-1)条件变形时,流动软化主要是片状α相的等轴化引起的。引入应变对材料常数α、n、A和Q的影响,建立了考虑应变的TC4钛合金Arrhenius本构方程,建立的本构模型精度较好,在800,850℃和10 s~(-1)条件以及在900,950℃和0.1 s~(-1)条件下,模型平均绝对误差分别为4.2%和4.3%。TC4钛合金的平均变形激活能为403 kJ/mol,平均应变速率敏感指数为0.26。     

低碳合金钢高温本构方程及动态再结晶行为研究

利用Gleeble-3800热模拟机对典型低碳合金钢实施了变形温度900~1100℃,应变速率0.01、0.1、1.0和10 s~(-1),最大真应变为0.6的等温压缩模拟试验。通过对试验数据的回归分析,建立了应变为0.3的表观常数与物理常数Arrhenius型本构方程、动态再结晶动力学模型及运动学模型。结果表明:表观常数与物理常数Arrhenius型本构方程预测值与试验值的相关系数分别为0.9921和0.9879,平均相对误差值分别为3.6753%和5.4266%;临界应变与峰值应变之间存在关系:εc=0.4969εp;在变形温度900~1100℃,应变速率0.01 s~(-1)与变形温度1000~1100℃,应变速率0.1 s~(-1)试验条件下材料发生明显动态再结晶。     

热处理Cu-Nb纳米复合线的结构和织构演变

采用Gleeble-3800型热模拟试验机对熔铸态和锻态TiBw/TA15复合材料进行高温压缩变形试验,研究不同状态TiBw/TA15复合材料在变形量70%、变形温度900～1150℃、应变速率0.01～10 s~(-1)条件下的热变形行为,建立热加工图,并分析该复合材料在热变形过程中的组织性能演变规律。结果表明,熔铸态TiBw/TA15复合材料的热加工工艺窗口为温度900～1150℃,应变速率2.72～10 s~(-1);温度1000～1100℃,应变速率0.01～0.03 s~(-1);温度1075～1130℃,应变速率0.01～0.13 s~(-1)。锻态TiBw/TA15复合材料的热加工工艺窗口为温度900～975℃,应变速率0.37～10 s~(-1);温度960～1025℃,应变速率0.01～0.37 s~(-1);温度1025～1150℃,应变速率0.01～10 s~(-1)。通过对比发现,锻态TiBw/TA15复合材料的热加工工艺窗口宽,热变形加工性能优于熔铸态。     

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.     

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。     

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).     

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.     

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.