碳含量对Ti-60合金时效过程中硅化物的影响

Ti-60合金在β和α β相区固溶处理后空冷,形成的片状组织和双态组织中没有硅化物析出.随后在700～800℃时效处理168 h,在α/β片层界面、α片层内及初生α相内析出S2类型的硅化物(Ti,Zr)6Si3.C的加入阻碍硅化物在界面处和基体中的形核和长大,降低硅化物的析出速率.随着合金中C含量的增加,显著减小时效过程中硅化物的析出尺寸,这是由于C的加入,基体中固溶Si的能力增加及Zr原子扩散速度降低所导致的结果.相同温度下时效处理,双态组织中析出的硅化物尺寸比片状组织大.时效温度升高,硅化物的析出直径增大.     

固溶时效对热轧态QAl10.9-5-5合金组织及性能的影响

采用OM、XRD等分别研究了850~980℃固溶、350~650℃时效工艺对热轧态QAl10.9-5-5合金的显微组织及力学性能的影响。结果表明:随着固溶温度的升高,热轧态QAl10.9-5-5合金中未溶的α、κ相逐步固溶到高温组织中,并在室温组织中以β′相出现,当固溶温度升至925℃时,合金基本为单一均匀的β′相组织,此时硬度达到最大值;在随后的时效过程中,随着时效温度的升高,原子扩散速率加快,细小的κ相不断从β′相中析出,并产生明显的沉淀强化作用;当时效温度为450℃,保温2h时,合金硬度值可达326HB;继续升高时效温度,合金中开始出现大量的α相,从而导致其硬度随之下降。综合比较,热轧态QAl10.9-5-5合金的较佳热处理工艺为925℃×1h固溶、450℃×2h时效。     

高强高韧Mg-8.5Gd-2.0Y-1.0Ag-0.4Zr合金的组织与性能

研究了高强高韧Mg-8.5Gd-2.0Y-1.0Ag-0.4Zr(wt.%)合金的显微组织和力学性能。结果表明,该合金铸态组织细小,主要由α-Mg固溶体、晶界析出相Mg5(GdY)以及分布在晶粒内部的Zr核组成;T4态时晶界析出相基本完全消失,但出现了一些方块相γ;合金具有明显的时效硬化效果,且随着时效温度的提高,合金的峰值时效硬度下降,峰值时间相应缩短。经200℃峰值时效处理后表现出极为优异的室温力学性能,抗拉强度(UTS)和延伸率分别达到396MPa和9.1%,显著的时效强化是该合金具有优异力学性能的主要原因。如此优异的强度和塑性在常规铸造镁合金中是极为罕见的,对于推广镁合金的应用具有重要意义。     

热处理对铸造Ti15-3合金显微组织和力学性能的影响

借助光学显微分析、ＴＥＭ和ＳＥＭ分析手段研究了不同热处理工艺对Ｔｉ１５－３合金显微组织和力学性能的影响。结果表明：合金在铸态时的组织特征为粗大的β相,由于合金中没有析出相的弥散强化作用,因而合金的强度低,在不同温度时效处理后,在晶内和晶界析出α相,随着时效温度和时效时间的增加,析出相不断粗化,与铸态相比,合金时效后强度大幅度提高而处伸率大幅度下降,在变形过程中,合金中的位错在析出相周围形成缠结,合     

热处理对Ti35Nb3.7Zr1.3Mo合金的组织与性能影响

依据钛合金相关设计理论设计了低弹性模量、中高强度、良好塑性的新型生物医用近β型Ti35Nb3.7Zr1.3Mo合金,研究了固溶温度和时效温度对合金组织和力学性能的影响。结果表明:随着固溶温度的升高,α相逐渐溶解,合金的强度和弹性模量尚未发生明显变化。在低温时效时析出脆性ω相;随着时效温度升高,逐渐析出α相,且α相逐渐粗化;合金的强度与弹性模量先升高,达到峰值后下降;延伸率先降低后升高。合金经750℃固溶和450℃时效后综合力学性能优良,可以满足生物植入材料力学性能的要求。     

热处理对Ti2448合金冷轧板组织和性能的影响

研究了热处理对Ti-24Nb-4Zr-8Sn(Ti2448)合金冷轧板材的显微组织和力学性能的影响,结果表明:Ti2448合金的杨氏模量和力学性能对其显微组织很敏感.在550-850℃,随着退火处理温度的升高Ti2448合金板材的晶粒长大,强度和杨氏模量降低而塑性提高;在400-500℃时效处理,合金中析出α相.控制时效时析出α相的形貌、含量和析出位置,可以调节合金强度、杨氏模量和塑性之间的匹配关系;控制热处理温度和时间可以实现高强度、低杨氏模量和良好室温塑性的匹配.     

挤压温度对AZT802镁合金组织和性能的影响

将铸态AZT802合金分别在350℃、380℃和400℃下挤压,随后进行T5时效处理,研究不同挤压温度对AZT802镁合金挤压态和时效态组织和性能的影响。结果表明,当挤压温度为350℃时,晶粒尺寸分布不均匀,同时观察到大块的条状第二相沿挤压方向析出。当挤压温度高于350℃时,挤压态合金获得均匀等轴晶粒,第二相以颗粒状形貌沿晶界均匀分布。经T5时效处理后,颗粒状Mg_2Sn相均匀分布于基体中,Mg_(17)Al_(12)相以连续相和非连续相析出,非连续析出相随时效前挤压温度的升高而逐渐增多。力学性能测试结果表明,AZT802合金在380℃下挤压,并进行175℃(3h)T5时效处理后,获得最佳综合力学性能。     

生物医用Ti-Nb系合金组织与性能研究

本文结合相关参考文献,研究了Ti9Nb13Ta5Zr合金的显微组织与力学性能。研究结果表明,随着固溶温度的升高,晶粒尺寸逐渐降低,强度和弹性模量呈现出下降的趋势,但是塑性明显升高;合金经过时效处理后,基体组织中开始有针状的α相析出,同时合金的强度与弹性模量相对于固溶态明显升高。     

Inconel 740H合金750℃长期时效后的组织稳定性

对Inconel 740H合金管材在750℃进行500~3000h的无应力时效实验,采用热力学模拟,OM,FEG-SEM,显微硬度测定等方法研究了合金微观组织及显微硬度的变化趋势。结果表明:供货态(固溶处理)管材的合金成分及拉伸性能等均满足ASME要求,管材合格;长期时效后合金的主要析出相为γ′及M23C6,无η,σ等有害相析出。随着时效时间的延长,γ′粒子的粗化速率较快,其规律符合LSW熟化理论,M23C6相尺寸变化不明显;合金的显微硬度呈现先上升后下降的变化趋势,但整体波动较小。长期时效后合金组织及显微硬度的变化表明Inconel 740H在750℃/3000h条件下的组织稳定性较好,可用于进一步进行持久等长时力学性能的检验。     

热处理对Ti6242S钛合金组织性能及探伤的影响

采用固溶时效及退火两种工艺对Ti6242S钛合金大棒材进行热处理,研究了不同热处理坯料尺寸对显微组织、力学性能以及探伤杂波水平的影响。结果表明:固溶时效态Ti6242S钛合金大棒材越靠近心部初生α含量越高,而退火态显微组织中等轴初生α相含量较固溶时效态更高;普通退火处理后蠕变性能较差,固溶时效态综合性能最好;固溶时效处理后大棒材水浸探伤底波的均匀性略有提高,而普通退火无此效果。     

Fe86Zr5.5 Nb5.5 B3非晶合金的超高压烧结成型

为了获得致密的块状Fe86Zr55Nb55B3纳米晶合金,研究了高压快速烧结工艺参数对样品致密度和α-Fe相晶粒尺寸的影响.结果表明:快淬球磨破碎非晶粉末在5.5 GPa/3min烧结条件下,当Pw=1150 W后,可获得相对密度为98.3%、单相α-Fe纳米晶(16.3 nm)块体合金,且随着Pw和t的增加,样品相对密度和α-Fe相晶粒尺寸均略有增加,样品典型的比饱和磁化强度σs和矫顽力Hc分别为119.6 emu/g,63.8 Oe.     

Thermodynamic properties of Pt5La,Pt5Ce,Pt5Pr,Pt5Tb and Pt5 Tm intermetallics

The Gibbs’ energies of formation of Pt₅La, Pt₅Ce, Pt₅Pr, Pt₅Tb and Pt₅ Tm intermetallic compounds have been determined in the temperature range 870–1100 K using the solid state cell: $$Ta,M + MF_3 /CaF_2 /Pt_5 M + Pt + MF_3 ,Ta$$ . The reversible emf of the cell is directly related to the Gibbs’ energy of formation of the Pt₅M compound. The results can be summarized by the equations: $$\begin{gathered} \Delta G_f^ \circ \left\langle {Pt_5 La} \right\rangle = - 373,150 + 6 \cdot 60 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Ce} \right\rangle = - 367,070 + 5 \cdot 79 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Pr} \right\rangle = - 370,540 + 4 \cdot 69 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Tb} \right\rangle = - 372,280 + 4 \cdot 11 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Tm} \right\rangle = - 368,230 + 4 \cdot 89 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \end{gathered} $$ relative to the low temperature allotropic form of the lanthanide element and solid platinum as standard states The enthalpies of formation of all the Pt₅M intermetallic compounds obtained in this study are in good agreement with Miedema’s model. The experimental values are more negative than those calculated using the model. The variation of the thermodynamic properties of Pt₅M compounds with atomic number of the lanthanide element is discussed in relation to valence state and molar volume.     

Synthesis of tritium-labeled 5-fluorouracil and 5-fluorocytosine

The effect of various catalysts and temperature on the solid-phase isotope exchange of 5-fluorouracil and 5-fluorocytosine with tritium was studied. The isotope exchange yielding the desired compounds is accompanied by dehalogenation and hydrogenation of the 5,6-double bond of the pyrimidine ring. Performing the reaction at a temperature below 160°C allowed the process to be carried out selectively, i.e., with the preservation of the functional groups and double bond in the starting compound. The yields of various products formed in the reactions of tritium with the above compounds were estimated. Synthesis conditions were found, and tritium-labeled 5-fluorouracil and 5-fluorocytosine were prepared with the molar radioactivity of 0.45 Ci mmol⁻¹ (16.7 TBq mol⁻¹) and 4.4 Ci mmol⁻¹ (0.16 PBq mol⁻¹), respectively, and with the purity exceeding 98%.     

Evolution of the structure of Ti-5Al-5Mo-5V alloy deformed by high pressure

Specific features of straining of the Ti-5Al-5Mo-5V (VT22) alloy deformed by high pressure (cold and hot screw extrusion) are studied depending on its phase composition by the methods of X-ray diffraction analysis, optical microscopy, and electron microscopy. It is shown that the application of high pressure and complex schemes of deformation in combination with the action of temperature enables one to attain high levels of strains in the material without fracture. Under these conditions, new structures (containing nanosized particles responsible for the new properties) are formed. The mechanisms of deformation on the mesolevel are specified. It is shown that, in the process of cold hydroextrusion, the alloy in the one-phase β-state is deformed according to the mechanism of rotation via the formation of strain-induced martensite, whereas the alloy in the two-phase state is deformed according to the mechanism of bending. It is also shown that the mechanisms of deformation strongly depend on the initial phase composition of the alloy. The procedure of hot screw extrusion is characterized by the action of several mechanisms of deformation. Knowing these mechanisms, it is possible to choose the required modes of treatment and obtain structures guaranteeing the optimal combination of strength and plasticity. __________ Translated From Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 3, Pp. 57–64, May–June, 2006.     

Characterization of coprecipitated ferroelectric Bi2 VO5·5

Fine powders of orthorhombic bismuth vanadate (Bi₂ VO_5·5) have been synthesized by coprecipitation method. Powder X-ray diffraction and electron microscopic techniques have been used to characterize these samples. The formation of the monophasic Bi₂ VO_5·5 was confirmed. The compacted powders sintered at 1070K have been characterized for their dielectric properties as a function of both temperature (300–900 K) and frequency (100 Hz–10 MHz) and found to be superior to those obtained by the conventional solid-state reaction route.     

DFT方法对LaNi5及LaNi5H0.5晶体结构的预测

根据密度泛函理论,以扩展平面波函数为基集,采用超软赝势技术,对LaNi5 储氢合金及其吸氢后的晶胞模型进行了优化,从理论上给出了其结构参数及性质。计算结果表明该方法能较好地符合 LaNi5 及其氢化物结构的实验值,为该类合金的结构预测提供了一个理论估算途径。此外,根据模型的结构参数分析了LaNi5 中不同间隙位的吸氢稳定性,解释了影响间隙位稳定性的因素。     

GAMS5

The construction of the double-crystal γ-spectrometer GAMS5 was finished recently and the instrument is now operational. Measurements with double flat crystals were carried out and we will report here on the progress concerning the characteristics of the spectrometer.     

Ordering of Cubic Titanium Monoxide into Monoclinic Ti5O5

The structures of ordered and disordered cubic Ti _x O _z = TiO _y (y= z/x) phases containing both Ti and O vacancies were studied by x-ray diffraction. The results demonstrate that annealing TiO _y with y= 0.9–1.1 below 1300 K leads to the formation of a monoclinic ordered Ti₅O₅phase (sp. gr. C2/m(A12m/1)). Symmetry analysis of the monoclinic Ti₅O₅superstructure indicates that the TiO _y –Ti₅O₅ordering transition is defined by the {k ₁₀} Lifshits and {k ₄} and {k ₁} non-Lifshits wavevector manifolds. The ordering is shown to be a first-order transition accompanied by a decrease in the unit-cell volume of the parent lattice. The Ti and O distribution functions in titanium monoxide are calculated, and the Ti- and O-site near-neighbor environments in the monoclinic Ti₅O₅superstructure are identified. The region of possible long-range-order parameters is outlined.