生物医用Ti-3Zr-2Sn-3Mo-25Nb合金的弹性变形行为(英文)

研究了新型医用近β钛合金Ti-3Zr-2Sn-3Mo-25Nb(质量分数,%)不同组织状态的的弹性变形行为。具有单一β相的固溶态合金表现出典型的双屈服现象,在与应力诱发马氏体相关的第一屈服之前显示出一定程度的非线性弹性变形特征。时效处理后,由拉伸测试所得的合金初始弹性模量的变化与时效析出α相体积含量没有明显的对应关系;然而弹性模量随着β晶粒与α相尺度的减小而增大。提出合金加载过程中,晶格剪切被细小α相有效阻止,这将导致合金较高的静态弹性模量的出现以及非线性弹性特征的减弱。     

退火时间对冷轧态Ti86.5Nb7.5Mo4Sn2合金显微组织及其超弹性的影响

用水冷铜模吸铸法制备Ti86.5Nb7.5Mo4Sn2(at%,下同)合金,将合金在室温下进行了冷轧(变形量为80%),然后在973 K,不同保温时间下对合金进行了退火。研究了退火时间对合金显微组织及其超弹性的影响。结果表明,冷轧后得到了晶粒细长的变形组织,该组织在973 K下固溶处理后发生了再结晶,形成了细小的等轴晶粒组织。冷轧后的合金组织主要由β相以及少量的α′′相组成,而固溶后的合金组织主要由β相以及少量的α相和α′′相组成。随着固溶时间延长,合金的晶粒尺寸逐渐增大。固溶处理后的合金在室温下表现出超弹性,其马氏体诱发临界应力σSIM与晶粒尺寸的关系满足Hall-Petch方程。因此,减小合金晶粒尺寸,可有效提高合金的超弹性性能。     

组织对医用Ti-3Zr-2Sn-3Mo-25Nb钛合金低周疲劳行为及变形机制的影响

研究了具有2种不同组织（固溶态、时效态）的Ti-3Zr-2Sn-3Mo-25Nb(TLM)合金在室温应变控制的低周疲劳循环变形行为及微观变形机制。结果表明：TLM合金的循环硬化/软化行为与应变幅和组织密切相关。固溶态合金的低周疲劳寿命更高,且弹性模量均随循环周次和总应变幅的增大,从保持不变到急剧增加,时效态的弹性模量则在循环变形过程中基本保持不变。微观组织特征表明,固溶态合金的循环变形机制主要依赖位错滑移、变形诱发的α″马氏体和独特的“Z”型β孪晶协同作用,而时效态合金则只是以位错滑移为主。     

固溶态Ti-41Nb合金的微观组织与力学行为研究

采用光学显微镜、力学性能测试和原位同步辐射高能X射线衍射等方法系统地研究了固溶态Ti-41Nb合金的微观组织与力学行为。结果表明,Ti-41Nb合金经800℃固溶淬火处理后,其等轴β基体上分布着微量的板条状α″马氏体,呈现典型的双相结构。在拉伸过程中,固溶态Ti-41Nb合金除发生弹性变形外,还发生了β→α″应力诱发马氏体相变。应力诱发马氏体相变在0.0%～3.3%应变范围内较剧烈,在3.3%～4.0%应变范围内相对轻微。在随后的卸载过程中,固溶态Ti-41Nb合金发生了弹性回复,同时伴随着α″→β逆马氏体相变。卸载后,固溶态Ti-41Nb合金中仍有大量的α″马氏体未转变为β母相,这导致合金仍有2.9%的残余应变。     

Ti-7.5Nb-4Mo-2Sn-1.6Si合金的显微组织及超弹性行为

采用真空电弧熔炼法制备Ti-7.5Nb-4Mo-2Sn-1.6Si（原子百分比,at%）合金,在800 ℃对合金进行了热压处理（变形量为50%）, 然后在700 ℃对合金进行固溶处理20 min,对其显微组织和超弹性性能进行了研究。该合金显微组织由b相和少量a″相组成,在b相基体中有弥散细小的Ti₅Si₃颗粒的析出。与Ti-7.5Nb-4Mo-2Sn合金相比,由于Si的固溶强化和Ti₅Si₃的弥散强化作用,含1.6at%合金的应力诱发马氏体相变临界应力得到提高,从而使该合金在室温下表现出更好的超弹性。随着预变形量的增加,该合金的超弹性回复率降低。在预变性量为4%条件下,对该合金进行循环拉伸-卸载“训练”,在经过11次循环后,合金的超弹性得到进一步改善。     

Ti-22Nb-6Zr(at%)合金的超弹性和形状记忆效应

用弯曲法和拉伸法测定Ti-22Nb-6Zr（at％）合金的超弹性和形状记忆效应，研究固溶处理温度对Ti-22Nb-6Zr合金组织结构及性能的影响。结果表明：固溶处理后Ti-22Nb-6Zr合金的室温组织为单一的β相，晶粒尺寸随固溶处理温度升高而增大；合金的静态弹性模量小于30GPa；Ti-22Nb-6Zr合金具有良好的超弹性和一定的形状记忆效应。室温下变形，合金的超弹性和形状记忆效应随固溶处理温度升高而提高。900℃固溶处理后的合金在室温下拉伸变形，应变为5％时，总的最大回复应变达4．12％，其中超弹性回复应变为3．91％，记忆回复应变为0.21％。     

应变速率对β固溶Ti-10V-2Fe-3Al合金应力诱发马氏体相变的影响

研究应变速率对β固溶处理的Ti-10V-2Fe-3Al合金应力诱发马氏体相变的影响。结果表明,随着应变速率由5×10-4 s-1增加到1 500 s-1,合金都发生应力诱发马氏体转变,且诱发应力随着应变速率的增加而增加。金相形貌及XRD分析显示,在所有的应变率下,合金拉伸后的微观组织均由针片状α″相和β基体相组成。应用热激活界面运动模型及拉伸过程的温度升高解释了随着应变速率的增加,诱发应力增加的现象。     

Co含量对Fe-30Ni-xCo-10.5Al-3Nb-0.05B形状记忆合金组织与伪弹性的影响

熔炼了Fe-30Ni-xCo-10.5Al-3Nb-0.05B(x=0、9、18、22,原子分数,%)多晶合金,将合金冷轧后进行固溶和600℃下的时效处理,时效时间为60 h。应用扫描电镜、X射线衍射仪研究了合金组织和物相的变化,并对合金进行了室温下的硬度和伪弹性测试。结果表明:Co含量为0%时,时效后晶内析出γ'和β两相;Co含量为9%～22%时,时效后晶内析出单一的γ'相;随着Co含量的增加,合金晶粒大小逐渐增加,γ'相的粒径也会发生变化。Co含量为0%的合金表现出超弹性,最大可回复应变为5.87%;Co含量为9%～22%的合金表现出伪弹性,其中,Co含量为18%的合金伪弹性最佳,形状回复率达84.00%,可回复应变达5.25%。合金的应力-应变曲线显示,合金伪弹性的来源除了应力诱发的马氏体相变,还存在其它机制。     

循环热处理对3J33（C）马氏体时效钢组织、性能的影响

3J33（C）马氏体时效钢是以无碳（或超低碳）铁镍马氏体为基体的时效强化型高弹性合金。采用工业电炉处理合金,高温固溶处理后,再经过4次变温循环相变,基体组织由高温固溶后220μm的粗大等轴晶细化为15μm左右的均匀细小晶粒。进一步时效处理后,合金抗拉强度、屈服强度、弹性极限、硬度提高10%以上,断面收缩率、断后伸长率、冲击吸收功提高30%以上。     

热处理对铸态60NiTi合金第二相析出与硬度的影响

利用OM、XRD、SEM、EDS和DSC等分析测试手段研究了不同热处理方式对60NiTi合金中第二相析出,及其对马氏体转变和硬度的影响。结果表明:固溶后水淬处理能显著提高铸态60NiTi合金的硬度,但炉冷处理却显著降低合金的硬度。400℃时效略微降低固溶后水冷合金的硬度,但长时间时效对硬度的影响不大。Ni_3Ti相的大量固溶是固溶水冷处理显著提高铸态合金硬度的原因,而固溶后炉冷合金硬度下降则来源于更多Ni_3Ti相的析出。60NiTi合金的硬度取决于马氏体转变发生的难易程度。     

GdF_3:Ce~(3+),Ln~(3+)(Ln~(3+)=Eu~(3+),Tb~(3+),Dy~(3+),Sm~(3+))纳米晶体的制备与发光性能研究

应用共沉淀法,制备共掺同一敏化剂(Ce3+)和不同激活剂(Tb3+,Eu3+,Sm3+,Dy3+)的GdF3纳米晶体。在单一波长(254nm)紫外光的激发下,掺杂不同镧系激活离子的样品能够发射出不同颜色的明亮可见发光,因而适用于多色生物标记。     

三自由度并联机构（3SPS 3SRR）的位置分析

针对一种3SPS-3SRR并联机构,运用符号法对该机构进行位置分析建模及求解。构建动、静坐标系,通过矩阵转换对机构建立约束方程,运用Sylvester消元方法进行消元得到机构单变元输入输出方程,求得机构位姿的封闭解。最后进行实例求解,得到该机构处于一般姿态的32组实数解,并使机构处于特殊位姿,将所得封闭解与预估解对比,从而验证该位置求解模型的正确性。基于符号法的3SPS-3SRR并联机构位置分析模型具有准确、高效的特点,规避了基于数值法的诸多缺点,对该机构的深入分析具有重要理论意义及实用价值。     

Thermodynamic analysis of the CsNO3-KNO3-NaNo3 system

The thermodynamic properties of the CsNO₃-KNO₃-NaNO₃ system have been derived from an optimization procedure using experimental and published information concerning phase diagram and thermodynamic data for the constituent binary systems and ternary liquid phase. The results are in very close agreement with the experimental data.     

Phase diagrams of binary systems: AgNO3KNO3 and AgNO3 -@#@ NaNO3

AgNO₃-KNO₃ and AgNO₃-NaNO₃ phase diagrams were drawn using a simultaneous thermal analysis technique in the range 373 to 623 K. The apparatus is described briefly. Figure 1 shows a continuous solid solution in equilibrium with the liquid phase. It exhibits a eutectoid mixture (20 mol% NaNO₃) at 380.7 K. Figure 2 shows a eutectic mixture (45 mol % KNO₃) at 413 K, a eutectoid mixture (20 mol % KNO₃) at 409 K, and a continuous invariant at 404 K.     

3-D or not 3-D

When developing mathematical models of physical phenomena, physical scientists have been limited to two-dimensional solutions. In some cases, those solutions may be qualitatively correct, but in many others, the solutions are far from reality. This paper presents three examples of the limitations of two-dimensional modeling :diffusion-limited electrolytic reduction of a liquidproduct from a liquid electrolyte, morphological development of a solid dendrite, and behavior of a two-phase fluid under shear.     

BiFeO3-BaTiO3-LaFeO3三元多铁性陶瓷材料的制备及性能

采用固相法制备了1-x(0.71BiFeO3-0.29B aTiO3)-xLaFeO3 (x=0.0,0.1,0 2,0 3,0 4,0.5)三元多铁性陶瓷材料,并研究了LaFeO3含量对陶瓷物相结构、微观组织、电学性能和磁电耦合性能的影响。结果显示,所有陶瓷均为单一钙钛矿结构,但随LaFeO3含量的增加,伴随着结构相变。所得陶瓷晶粒尺寸均匀,表现出良好的微观形貌,陶瓷晶粒随LaFeO3含量的增加而明显变小。虽然LaFeO3的加入在一定程度上降低了陶瓷的介电常数,但分析发现,x=0.1时能降低陶瓷的漏导,其漏电流达到了最小值,在10-7~10-8 A/cm2数量级,并且该陶瓷的剩余极化强度Pr和磁电耦合系数αME均达到最大值,分别为0.45μC/cm2和132.21 mV/cm·Oe (120 kHz)。因此,与0.71BiFeO3-0.29BaTiO3陶瓷相比,添加少量LaFeO3可以在一定程度上增加陶瓷的铁电性和磁电耦合性能。     

3

In this paper, a planning algorithm for multi-path/multi-layer circular locus is poposed. The algorithm is applied to weld the nipples on the header of boiler. Multi-path/multi-layer circular locus is planned according to three teaching points, which is lapped head-on-end to satisfy the requirement of technology. For the nipples wherever they are arranged radially or axially, even if there are errors caused by positioning and thermal deformations, providing that nipple's position and orientation relative to the teaching one can be measured, the multi-path/multi-layer circular locus can be planned without teaching any more. The algorithm has been applied in welding robot for manufacturing power station' boiler.     

Electronic structures of semiconducting FeGa3, RuGa3, OsGa3, and RuIn3 with the CoGa3- or the FeGa3-type structure

Electronic structure of FeGa₃, RuGa₃, OsGa₃ and RuIn₃ with the crystal structures belonging to the space group of P4n2 (No. 118), which is usually referred to as the CoGa₃-type structure, and P4₂/mnm (No. 136), which is usually referred to as the FeGa₃-type structure, have been calculated using a first-principle pseudopotential method based on the density-functional theory within the local density approximation (LDA) with the generalized gradient correction. All of them have the similar band structure in that the valence band maximum occurs at or near A and the conduction band minimum occurs at a point between Z and Γ. From the total energies calculated, compounds with the FeGa₃-type structures are more stable than those with the CoGa₃-type structures. The band gaps of FeGa₃, RuGa₃, OsGa₃ and RuIn₃ with the FeGa₃-type structure are about 0.50, 0.26, 0.68, and 0.30 eV, respectively, which are wider than those with the CoGa₃-type structure. Calculated band gaps are wider than the observed gaps, which is unusual in the LDA calculation.     

Features of feathery γ structure in a near-γ TiAl alloy

This work characterizes the feathery-like structures produced in a Ti–46.8Al–1.7Cr–1.8Nb (at.%) alloy during rapid continuous cooling from the α domain. Their morphology and crystallography are described using different microscopy and orientation mapping techniques. These feathery-like structures are divided into many small domains, characterized by low-angle misorientations (rotated less than 15°) between the domains. The domains comprise multiple parallel γ lamellae and rare traces of α₂. These lamellae follow the Blackburn orientation relationship and have a {1 1 1}_γ habit plane. Two types of γ-feathery structures were identified according to their location and crystallography. The grain-boundary γ-feathery structures originate from lamellar structures that grow into a neighboring grain. Alternatively, the internal γ-feathery structures are located in the interior of prior α grains and show an average misorientation of 36° around one $〈100{〉}_{{\mathrm{\gamma }}_{\text{L}}}$ axis of the lamellar structure in which it is embedded. This paper describes these two γ-feathery structures in detail and discusses their development in light of the mechanisms available in the literature, particularly sympathetic nucleation.     

PMN-PNN-PT单晶的固相法生长研究

采用两步法和埋入PMN-PT单晶为模板的等离子放电烧结（SPS）技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷，随后在1200℃下退火100h来诱导晶体的生长。实验结果表明，PMN-PNN-PT单晶〈111〉方向的生长速度明显快于〈001〉方向，而〈111〉方向生长的晶体形状为V字形，这是由钙钛矿结构的生长机理决定的，钙钛矿结构晶体的生长是通过〈001〉方向的层状生长来实现的。