Al-Ti-B晶粒细化合金中的有效形核相

研究了ＡｌＴｉＢ晶粒细化合金中各化合物相ＴｉＡｌ３、ＴｉＢ２和ＡｌＢ２对铝晶粒的细化作用。结果表明，ＴｉＡｌ３相是有效形核相，ＴｉＢ２和ＡｌＢ２相不能单独作为形核相，Ｂ对ＡｌＴｉＢ的细化作用有显著影响，但Ｂ及硼化物不能单独影响细化过程，而是富集在ＴｉＡｌ３相中对细化过程产生重要影响。

电解低钛铝合金的相组成和细化机理的研究

采用在电解过程中直接形成低钛铝合金的方法 ,研究了电解铝中不同含 Ti量及其在合金中存在不同第二相对细化效果的影响。结果表明 ,电解掺 Ti的细化效果好于纯铝加 Al- Ti中间合金 ,钛在电解铝中起到异质形核和抑制晶粒长大的作用。

钛合金中ω相变的研究进展

钛合金中的ω相及其相变对合金的组织性能影响较大,因此近年来ω相变也成为钛合金研究中的热点问题之一。从ω相的形成、分解、组织形貌以及ω相辅助α形核的角度总结归纳了相关研究报道,对比了相关模型观点的优缺点,阐述了ω相目前仍存在的学术分歧。

落管中Co-Sn共晶合金的快速凝固

采用落管无容器处理技术实现了Co-34.2％Sn共晶合金在微重力条件下的快速凝固,获得了直径为100～900μm液滴的凝固组织。研究发现,随着过冷度的增大,共晶生长由层片共晶向不规则共晶转变,实验中获得了0～309K的过冷度,最大过冷度达到0.22T_E,理论分析与实验结果表明,γCo_3Sn金属间化合物是领先形核相;过冷度大于213K时,金属间化合物γCo_3Sn将取代层片共晶成为领先生长相;Co-Sn合金的共晶共生区偏向于富Co方,其成分范围为19.0％～39.6％Sn,实验达到的过冷度范围内,αCo固溶体和γCo_3Sn金属间化合物均以溶质扩散控制方式生长。

乳腺血管内皮肉瘤一例报告

乳腺血管内皮肉瘤一例报告王学范医师刘日圣，潘心海临朐县人民医院（２６２６００）女性患者，２２岁、未婚。乳房发现肿块７月余，于９０年４月１４日突然大出血来院就诊。查体：病人重度贫血貌，脉博、血压测不到、呼吸微弱、神志不清。左乳房肿胀为３０×２５×１５ｃ...

Improving in plasticity of orthorhombic Ti_2AlNb-based alloys sheet by high density electropulsing

In order to optimize the ductility of orthorhombic Ti2AlNb-based alloys sheet,Ti22Al27Nb sheet was treated by high density electropulsing（J max =6.80 7.09 kA/mm2,tp =110 μs） under ambient condition.Microstructures were observed by SEM,and the tensile properties were also studied using uniaxial tension tests.The experimental results show that electropulsing can refine the microstructures of Ti22Al27Nb sheets.The specimen with the fine and homogeneous microstructures has good plasticity,and its elongation reaches 19.4%.The mechanism about the effect of electropulsing treatment on the microstructure of Ti22Al27Nb sheets was discussed.It was thought that the increase in nucleation rate during phase transformation and a very short treating time were regarded as the main reasons of producing smaller grains and increase in the plasticity by electropulsing.

Magnesium vapor nucleation in phase transitions and condensation under vacuum conditions

Recent findings related to coagulable magnesium vapor nucleation and growth in vacuum were assessed critically, with emphasis on understanding these processes at a fundamental molecular level. The effects of magnesium vapor pressure, condensation temperature, and condensation zone temperature gradient on magnesium vapor nucleation in phase transitions and condensation from atomic collision and coacervation with collision under vacuum conditions were discussed. Magnesium powder and magnesium lump condensates were produced under different conditions and characterized by scanning electron microscopy （SEM） and energy-dispersive X-ray spectroscopy （EDS）. The right condensation zone temperature approach to the liquid transition primarily improved the magnesium vapor concentration rate. The gas-solid phase transition was primarily inhibited by setting a small condenser temperature gradient. Under the right condensation temperature and temperature gradients, increasing magnesium vapor partial pressure improved crystallization and reduced the oxidation rate.

Enhancement of nucleation of diamond films deposited on copper substrate by nickel modification layer

A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.

Time-temperature-property curves for quench sensitivity of 6063 aluminum alloy

The quench sensitivity of 6063 alloy was investigated via constructing time-temperature-property（TTP） curves by interrupted quenching technique and transmission electron microscopy（TEM） analysis.The results show that the quench sensitivity of 6063 alloy is lower than that of 6061 or 6082 alloy,and the critical temperature ranges from 300 to 410℃ with the nose temperature of about 360℃.From TEM analysis,heterogeneous precipitate β-Mg2Si is prior to nucleate on the（AlxFeySiz） dispersoids in the critical temperature range,and grows up most rapidly at the nose temperature of 360℃.The heterogeneous precipitation leads to a low concentration of solute,which consequently reduces the amount of the strengthening phase β＇＇ after aging.In the large-scale industrial production of 6063 alloy,the cooling rate during quenching should be enhanced as high as possible in the quenching sensitive temperature range（410-300℃） to suppress the heterogeneous precipitation to get optimal mechanical properties,and it should be slowed down properly from the solution temperature to 410℃ and below 300℃ to reduce the residual stress.

Nucleation interface of Al-Sb alloys on single crystal Al_2O_3 substrate

Lattice structure information of heterogeneous nucleation at nucleation interface was present.The crystal orientation,and interfacial structure characteristic of liquid Al alloys nucleated on the basal surface(0001)Al2O3single crystal substrate were identified by X-ray diffraction(XRD),scanning electron microscopy(SEM)and high resolution transmission electron microscopy(HRTEM)analysis.The preferred crystal orientations of pure Al and Al-1%Sb(mass fraction)alloy adjacent to the nucleation interface were examined as(200)and(220)planes of Al,respectively,and two corresponding orientation relationships were obtained.An improved nucleation efficiency and refined grains were attributed to both the reduced interplanar spacing of preferred orientation and the decrease of lattice misfit from16.4%to7.0%in Al-1%Sb/Al2O3nucleation group.

Simplification of Double Folding Model Calculations in Study of Interaction Between Two Deformed Nuclei

The Double Folding （DF） model calculation of the internuclear potential in heavy-ion interactions when the participant nuclei are deformed in their ground states involves a six-dimensional integral. Using the multipole expansion in these calculations, the DF six-dimensional integral reduce to the sum of the products of three single-dimensional integrals. In this paper we have presented a procedure for the calculation of the radius dependent functions in the multipole expansion of the nuclear density and their Fourier transforms. We have also reduced the DF model integrals to the sum of the single dimensional integrals using the obtained relations for the radius dependent functions in the multipole expansion and their Fourier transforms.

Karyotype Analysis of the Fiddleneck （Phacelia tanacetifofia Benth.）

Two varieties of fiddleneck （Phacelia tanacetifolia Benth.） plant were determined for visualizing somatic chromosomes. The 4-5 days old root tips were pre-treated in 6% a-monobromonaphtalane in ＋4 ℃ for 7.5 h, then fixed in glacial acetic acid for 30 min and transferred to 70% ethanol for long storage. When the root tips were analyzed, they were hydrolyzed with 1 N HCI for 13 min at room temperature （25 ℃）. After hydrolyzing, root tips were stained with 2% aceto orcein in darkness for 2.5 h. The squash method for preparation was used for chromosomal investigations. The chromosome length （C）, relative length （RL）, the long arm （L） and short arm （S） lengths, arm ratio （AR; L/S） and centromefic index （S/C） were calculated for caryologic parameters. The ideograms and detailed chromosome morphology measurements of the species were performed by the use of MicroMeasure 3.3. According to results, fiddleneck （Phacelia tanacetifolia Benth.） has 2n = 22 chromosomes and the karyotype formulas of two varieties of fiddleneck were 16 median and 6 submedian （16 m ＋ 6 sm）.

Tailored microstructures and strengthening mechanisms in an additively manufactured dualphase high-entropy alloy via selective laser melting

Dual-phase high-entropy alloys(DP-HEAs)with excellent strength-ductility combinations have attracted scientific interests.In the present study,the microstructures of AlCrCuFeNi3.0DP-HEA fabricated via selective laser melting(SLM)are rationally adjusted and controlled.The mechanisms engendering the hierarchical microstructures are revealed.It is found that the AlCrCuFeNi3.0fabricated by SLM at the scanning speed of 400 mm s-1falls into the eutectic coupled zone,and increasing the scanning speed will make this composition deviate away from the eutectic coupled zone due to the increased cooling rate.The enrichment of Cr and Fe solutes with large growth restriction values ahead of the solid/liquid interface can develop a constitutional supercooling zone,thus facilitating the heterogeneous nucleation and nearequiaxed grain formation.The synergy of the near-eutectic DP nano-structures and near-equiaxed grains instead of columnar ones effectively suppresses cracking for the as-built DP-HEA.During the tensile deformation,the intergranular back stress hardening similar to the grain-boundary strengthening is discovered.Meanwhile,the near-eutectic microstructures comprised of soft face-centered cubic and hard ordered bodycentered cubic(B2)DP nano-structures lead to plastic strain incompatibility within grains,thus producing the intragranular back stress.The Cr-rich nano-precipitates inside the B2 phase are found to be sheared by dislocation gliding and can complement the back stress.Additionally,multiple strengthening mechanisms are physically evaluated,and the back stress strengthening contributes obviously to the high performances of the as-built DP-HEA.

Phase field simulation of solidification under supergravity

In order to understand the influence of supergravity on the microstructure of materials,crystal nucleation,dendritic growth,and polycrystal solidification under supergravity are investigated by using the modified nucleation theory and phase field models.Firstly,supergravity is considered in the nucleation theory by using pressure-dependent Gibbs free energy.It is found that the critical radius decreases and the nucleation rate increases when supergravity rises.Secondly,anisotropic heat transport is proposed in the phase field model to investigate the influence of supergravity on dendritic growth.Phase field simulations show that supergravity promotes the secondary dendritic growth in the direction parallel to supergravity.Finally,a multiply phase field model with pressure-dependent interfacial energy is employed to simulate the polycrystalline solidification under supergravity.Due to the depth-dependent pressure by supergravity,crystal grains are significantly refined by high pressure.In addition,gradient distribution of grain size is obtained in the solidification morphology of polycrystalline,which is consistent with previous experimental observations.Results of this work suggest that supergravity can be used to tune the microstructures and properties of materials.