Microstructure and heat treatment for Ni3Al-based single crystal alloy with different crystal orientations

Ni₃Al-based single crystal alloy IC6SX with different crystal orientations were prepared by seed crystal method. The microstructure and heat treatment of the alloy were investigated. The results showed that the microstructure of the alloy was in dendrite structure, and the crystal orientation had significant effect on the dendrite morphology of this alloy. The precipitated phases of (MoNi)₆C and NiMo appeared in the microstructure of the three alloys with different crystal orientations during solidification process. Compared with other two alloys, the volume fractions of precipitated phases of both (MoNi)₆C and NiMo was the most in the alloy with [111] orientation and the least in the alloy with [001] orientation. The solidus and liquidus temperatures of the alloy IC6SX tested by differential scanning calorimetry (DSC) were 1356 °C and 1387 °C, respectively. Meanwhile, the effect of different solution temperatures on the microstructure of the alloy with different orientations was studied. The results showed that the precipitated phases of (MoNi)₆C and NiMo were eliminated with the solid solution treatment under the condition of 1300 °C/10 h. However, the incipient melting of the alloys occurred due to the dissolution of low melting point phases. As the temperature dropped to 1280 °C, the area of incipient melting in the alloy with different orientations decreased gradually. However, there was no incipient melting appearing in the three alloys with different orientations when the solution treatment temperature dropped to 1260 °C.     

5A02铝合金板料深冲有限元模拟与实验研究

对5A02铝合金板料深冲过程进行了实验研究,并在率相关晶体塑性本构理论框架下,实现了5A02铝合金板料深冲过程的晶体塑性有限元模拟.研究了深冲过程中的制耳和板厚的分布情况,分析预测了极限拉深系数值;结果表明,晶体塑性有限元法模拟的制耳轮廓的高度和极限拉深系数值与实测值比较吻合,板料的厚度变化与实际情况一致.     

Dendrite morphology and evolution mechanism of nickel-based single crystal superalloys grown along the o0014 and o0114 orientations

Nickel-based single crystal superalloys oriented along the o0014 and o0114 lattice directions were produced by a bottom seeding technique in an attempt to understand the evolution mechanism of the dendrite grown along different orientations in the present study. The changes in primary dendrite arm spacing for single crystal with different orientations are also discussed. It was found that the dendrite morphologies of single crystal superalloy grown along o0114 were different from that of o0014. Firstly, the dendrites showed the irregular cruciforms and array in rows in a transverse section. Secondly, no typical primary dendrites were observed but the dendrite morphologies appeared like the letter ‘‘V’’ or ‘‘W’’ in a longitudinal section. The primary dendrite arms grew along the o0014 orientation from the bottom of the sample in the o0014 orientation. However, in the o0114 orientation, the single crystal developed by continuous side-branching along the [001] and [010] orientations. The primary dendrite arm spacing was as the function of the deviation angle f. It indicates that with the increase in the deviation angle f, the primary dendrite arm spacing first increased, and then decreased.     

微尺寸单晶金属应变突变现象的随机有限元分析

微米尺寸单晶柱体的压缩实验发现,在其塑性变形过程中应变会发生突变,致使塑性流动呈现明显的间歇性. 通过随机有限元方法,分析了微米尺寸和块体镍单晶柱体在混合加载方式下的间歇性塑性流动行为. 同时,结合镍单晶柱体的实验数据以及基于经典晶体塑性理论的有限元方法,对近期新建立的理论模型进行了分析研究. 结果表明:新理论模型能够捕捉应变突变的发生;对于块体材料,新模型计算结果与常规晶体塑性有限元结果以及实验结果均比较吻合;当单晶柱体尺寸减小至几十μm左右时,新模型预测结果仍然能够与实验结果保持一致;微柱体的塑性流动是通过一系列的应变突变行为实现的.     

Effects of subgrain size and static recrystallization on the mechanical performance of polycrystalline material: A microstructure-based crystal plasticity finite element analysis

In this paper, the effects of subgrain size and static recrystallization on the mechanical performance of polycrystalline material were investigated using a microstructure-based crystal plasticity finite element(CPFE) model. Firstly, polycrystalline microstructures with different mean subgrain sizes were prepared using simple assumption based on experimental observations, and intermediate microstructures during static recrystallization(SRX) were simulated by a cellular automata model adopting curvature driven grain/subgrain growth mechanism. Then, CPFE method was applied to perform stress analysis of plane strain tension on these virtual microstructures. The results show that the subgrains inside pre-existing grains have an effect on the heterogeneity of the stress distributions. The average stress decreases with increasing the mean subgrain radius. As grain/subgrain grows during SRX, the average stress also decreases. It can be deduced that well-defined and finer subgrain structure may strengthen the polycrystalline material, while grain/subgrain growth during SRX process will degrade the strength.     

α相与β相比例对TC6钛合金力学性能的影响

 通过热处理方法获得TC6钛合金3种典型组织,利用电液伺服材料试验机测定3种组织的静态力学性能,通过专用图形分析软件测定3种组织中α相与β相比例,对比分析了α相与β相比例对TC6钛合金静态力学性能的影响.结果表明:组织中α相比例增大(即β相比例减少)时,相应组织塑性也增大,而强度随着α相比例增大(即β相比例减少)而减小.     

气-液界面表面活性剂单分子膜BAM图像的模拟计算

对界面上不同结构缺陷所引起的分子排列和取向进行了组合,建立了分子的取向模型,利用光传播的电磁场理论,模拟出了布儒斯特角显微镜(BAM)的理论图像,并将其与实验观察得到的BAM图像进行了比较。结果显示:理论计算图像与实际BAM观察结果基本一致;复杂的BAM图案可由点缺陷和线缺陷组合得到。     

Zr-xNb-4Sn alloys with low Young’s modulus and magnetic susceptibility for biomedical implants

The microstructure, mechanical and magnetic properties of Zr–x (8, 9, 10, wt.%)Nb–4Sn alloys were investigated to obtain novel Zr-based alloy with low Young’s modulus and magnetic susceptibility for biomedical implants. After homogenization annealing, hot forging and solution annealing, Zr–8Nb–4Sn, Zr–9Nb–4Sn and Zr–10Nb–4Sn alloys were composed of β+α″ phase, β+α″ phase, β+ω phase, respectively. The temperature at which the α" and ω phase were transformed into β phase during the heating process was about 200 ​°C, and the phase transformation temperature decreased with the increase of Nb element. Among all the Zr–x (x ​= ​8,9,10)Nb–4Sn(wt.%) alloys, Zr–9Nb–4Sn alloy had the lowest Young's modulus of 46.6 ​GPa and the low magnetic susceptibility of 1.294 ​× ​10⁻⁶ cm³g⁻¹, which has a good application prospect for biomedical applications.     

α-(2,5-二甲基-3,4-二乙酰基吡咯基)萘的合成和晶体结构

 在酸性介质中,3,4-二乙酰基-2,5-己二酮与萘胺作用,合成得到了α-(2,5-二甲基-3,4-二乙酰基吡咯基)萘,用IR,1H-NMR,MS,HRMS对其进行了表征,并用X射线衍射测定了α-(2,5-二甲基-3,4-二乙酰基吡咯基)萘的晶体结构.该晶体属三斜晶系,P1空间群,晶体学数据为:a是0.8045(1)nm,b是1.0018(1)nm,c是2.0757(2)nm,α是80.09(1)°,β是82.66(1)°,γ是83.81(1)°,V是1.6281(3)nm³,Z是4,M_r是305.36,D_c是1.246×10³kg/m³,μ(M_oK_α)是0.080mm^-1,F(000)是648,在I>2σ(I)的独立可观测衍射点为3669个,最终偏差因子R是0.0406,W_R是0.0962.     

Deformation mechanism of fine structure and its quantitative relationship with quasi-static mechanical properties in near β-type Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr −2.9Zn alloy

The deformation mechanism of the fine structure composed of primary α phase (α_p) and acicular secondary α phase (α_s) on quasi-static mechanical properties is still not very clear. The main controversy is focused on the role of α_p in the mechanical behavior. In this paper, the microstructure of the heat-treated near β-type Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn alloy after tensile tests was observed by transmission electron microscopy (TEM). And the results showed that in the slight deformation region the dislocations were accumulated at the intersection of α_p and β matrix separated by α_s, while only a few dislocations nucleated in β matrix. In the severe deformation region, a large quantity of dislocations in both α_p and β matrix were observed. It can be inferred that α_p deformed firstly and then activated the deformation of β matrix, that is, the thickness of α_p and the inter-particle spacing of α_s played a dominant role in the deformation process. The quantitative relationship between the yield strength and the microstructure parameters is consistent with this inference. By adjusting the solution treatment parameters and the subsequent aging treatment, three fine structures were obtained, and the corresponding mechanical properties were determined. Furthermore, the yield strength can be described by the mathematical model σ_y ​= ​756.4 ​+ ​135.6/h_p^1/2 +32.2/d_s^1/2, where h_p and d_s are the thickness of α_p and the inter-particle spacing of α_s, respectively.     

Unit-cell design for two-dimensional phase-field simulation of microstructure evolution in single-crystal Ni-based superalloys during solidification

Phase-field simulation serves as an effective tool for quantitative characterization of microstructure evolution in single-crystal Ni-based superalloys during solidification nowadays. The classic unit cell is either limited to γdendrites along 001 crystal orientation or too ideal to cover complex morphologies for γ dendrites. An attempt to design the unit cell for two-dimensional(2-D) phase-field simulations of microstructure evolution in single-crystal Ni-based superalloys during solidification was thus performed by using the MICRESS(MICRostructure Evolution Simulation Software) in the framework of the multi-phase-field(MPF) model,and demonstrated in a commercial TMS-113 superalloy. The coupling to CALPHAD(CALculation of PHAse Diagram) thermodynamic database was realized via the TQ interface and the experimental diffusion coefficients were utilized in the simulation. Firstly, the classic unit cell with a single γ dendrite along 001 crystal orientation was employed for the phase-field simulation in order to reproduce the microstructure features.Then, such simple unit cell was extended into the cases with two other different crystal orientations, i.e., 011 and 111 . Thirdly, for 001 crystal orientations, the effect of γ dendritic orientations and unit cell sizes on microstructure and microsegregation was comprehensively studied, from which a new unit cell with multiple γdendrites was proposed. The phase-field simulation with the newly proposed unit cell was further performed in the TMS-113 superalloy, and the microstructure features including the competitive growth of γ dendrites,microsegregation of different solutes and distribution of γ′ grains, can be nicely reproduced.     

微裂纹起裂扩展机理的晶体相场模拟

【目的】研究初始晶向倾角为15°的样品分别在垂直和水平方向上,单轴拉应变作用下的纳观尺度裂口发射位错与裂纹扩展行为,了解韧性裂纹的生长特征和扩展规律,揭示纳米级韧性裂纹扩展机理及其对材料断裂的影响。【方法】采用晶体相场(PFC)方法观察15°晶向倾角下位错发射与裂纹扩展演化图及其对应的应力曲线图。【结果】垂直和水平不同方向拉应变作用下裂纹扩展方向不同,但裂纹都是韧性断裂模式扩展;当单轴拉应变作用达到临界值时,样品裂口开始发射滑移位错,随着外应力的增大,位错在滑移过程中留下一系列空位,空位长大连通形成裂纹并与主裂口相连,裂纹随着位错运动而扩展。【结论】在韧性裂纹扩展中,位错发射的运动对韧性裂纹扩展演化有重要影响。     

晶体结构对(Zn,Cd)S:Cu电致发光材料发光性能的影响

采用X射线衍射法定量测定了不同Cd2+含量下,(Zn,Cd)S:Cu,Cl电致发光粉的晶体结构成分.发现随着Cd2+的增加,材料中立方结构的含量逐渐减少,发光光谱向长波方向移动,而且亮度逐渐降低.利用相变使材料结构由六角结构向立方结构转变,大幅度提高了材料的发光亮度.     

中空纤维多孔膜基气体吸收传质性能研究

气相传质阻力是中空纤维多孔膜基气体化学吸收过程中的主要传质阻力。文中采用聚丙烯中空纤维膜组件、CO₂-空气-水和CO₂-空气-NaOH水溶液两种体系对膜基气体吸收过程的传质性能进行了研究。测定了不同气速和液速条件下的总传质系数。根据气液反应理论对实验结果进行分析,由实验和理论计算获得了气相分传质系数。通过进一步的拟合计算获得中空纤维多孔膜管内气相传质数学关联式Sh =0.0038Re^0.44Sc^0.33_.用此关联式计算得到的总传质系数与实验测得的结果进行了比较,一致性良好.     

Structural,elemental, optical and magnetic study of Fe doped ZnO and impurity phase formation

We have prepared a series of(ZnO)1-x(Fe2O3)x≤0.10bulk samples with various concentrations of Fe dopant by ball milling and investigated their structural, compositional, optical and magnetic properties by means of X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS),Raman spectrometer and vibrating sample magnetometer(VSM), respectively. Information about different impurity phases was obtained through Rietveld refinements of XRD data analysis. XPS results showed different valence states(Fe2+ tand Fe3+) supported by shaking satellite peaks in samples. With increasing Fe doping percentage, the crystal quality deteriorated and a shift of E2 low band(characteristic of ZnO) has been observed in Raman spectra. Energy band gap estimated from reflectance UV–vis spectroscopy showed shift for all bulk samples. The magnetic behavior was examined using a vibrating sample magnetometer(VSM), indicating ferromagnetic behavior at room temperature(300 K). The effective magnetic moment per Fe atom decreases with increase in doping percentage which indicates that ferromagnetic behavior arises from the substitution of Fe ions in the ZnO lattice.     

Zr-4合金薄板的织构与耐疖状腐蚀性能的关系

采用500 ℃/10.3 MPa过热蒸汽中腐蚀的方法,研究热处理及织构取向对Zr-4合金薄板耐疖状腐蚀性能的影响.样品在820 ℃-1 h加热快冷后,晶粒发生长大,得到了集中的 (0001)［11 20］和 (0001)［10 10］织构,这时耐腐蚀性能比较好的（0001）面基本平行于轧面,而样品四周的侧面是耐腐蚀性能较差的(11 20)和(10 10)面.样品经过这样热处理后,增加了Fe和Cr合金元素在 α-Zr中的过饱和固溶含量,提高了样品轧面的耐疖状腐蚀性能,但是样品的侧面上仍然会出现疖状腐蚀现象.耐疖状腐蚀性能的好坏与织构的晶体取向有关,只有当样品在1 000 ℃ β 相加热快冷,使 Fe和Cr合金元素在 α-Zr中的过饱和固溶含量进一步得到提高后,才能完全抑制疖状腐蚀现象.     

面心立方金属的基于位错密度的循环本构模型

在晶体塑性理论框架下,建立适用于面心立方金属多晶材料的基于位错密度的循环本构模型.在各向同性硬化律中总位错密度被离散为螺位错和刃位错两部分,考虑了位错增殖、湮灭和相互作用的演化机制,同时采用了修正的非线性随动硬化律,建立单晶的循环本构模型,通过显式尺度过渡准则,把该模型拓展到多晶尺度.应用该模型模拟了典型面心立方结构材料多晶铜的棘轮行为.数值模拟结果表明,该模型不仅可以从多晶尺度模拟材料的棘轮行为和循环硬化特征,还可以从单晶尺度预测不同晶向和不同应力水平下的棘轮行为.     

扫描电镜电子通道衬度技术研究铜双晶体循环饱和位错组态

通过对垂直晶界［５９１３］⊥［５７９］铜双晶体进行循环变形,借助于扫描电镜电子通道衬度技术研究了组元晶体及晶界附近的循环饱和位错组态,结果表明两个组元晶体的表面滑移程度不同,两个组元晶体中的循环饱和位错组态也明显不同,驻留滑移带只能在组元晶体Ｇ１中形成,驻留滑移带能够到达晶界但不能穿过晶界．讨论了组元晶体取向对双晶体的表面滑移形貌及饱和位错组态的影响以及驻留滑移带与晶界的交互作用．     

Microstructure and texture evolution of a near β titanium alloy Ti-7333 during continuous cooling hot deformation

The microstructure and texture evolution during continuous cooling hot deformation(CCHD) in a near β titanium alloy, named Ti-7Mo-3Nb-3Cr-3Al(Ti-7333), were investigated by using the electron backscattered diffraction(EBSD). The results indicate that the precipitation of secondary α phase was restricted by CCHD, and the morphology of primary α phase nearly had no change with the deformation and temperature drop. In contrast, βphase underwent more deformation and the grains tended to refine. This may be due to the dynamic recrystallization(DRX) of β phase, including continuous dynamic recrystallization(CDRX) and discontinuous dynamic recrystallization(DDRX). In addition, the textures of {110} 110 , {225} 520 and{115} 123 transformed to {100} 110 and {001} 100 during CCHD. Among these, the η-fiber component of {001} 100 was the dominant deformation texture in the deformed Ti-7333 alloy. Finally,continuous cooling has an important effect on the work hardening and softening during CCHD, contributing to the different flow behaviors at different cooling rates.     

Peculiar aging response of near b Ti–25 Nb–2Mo–4Sn alloy for biomedical applications

In this paper,aging response of a recently developed near β Ti-25Nb-2Mo-4Sn(wt%) alloy with high strength and low modulus was investigated intensively.The experimental results from X-ray diffraction and transmission electron microscopy showed that the aging production of the Ti-2524 alloy was(β+ω) or(β+α) even under the same aging treatment condition,depending on the pre-treatments prior to the aging.Solid evidence confirmed the competition between stable α phase and metastable ω phase during the decomposition of β phase on aging.Different aging response of Ti-2524 alloy can be attributed to high-density dislocations and grain boundaries which suppress the formation of ω,and alternatively promote a phase formation.This provides a thermo-mechanical approach to inhibit deleterious ω phase formation and assist fine α phase precipitation.Upon an appropriate aging treatment,superior mechanical properties of high ultimate tensile strength(1233 MPa) and low elastic modulus(77 GPa) were achieved in Ti-2524 alloy.