Ordering of hydrogen in the intermetallic compound Ti3Sn

IT is well known^1,2 that titanium hydride can form in thin foils of titanium alloys during chemical or electropolishing. The purpose of this communication is to show that, under similar conditions for Ti₃Sn, hydrogen orders in solution and does not form hydride precipitates. The alloy used in this work was induction melted and cast under argon from Osaka 160 Ti (total O, N, and C 700 ppm) and Pass no. 1 tin (99.98 pct). The final composition was Ti-24.8 wt pct Sn.     

Ti在铁素体中的平衡固溶度

基于Thermo-Calc和相关文献测试数据所推导出的Fe2Ti在铁素体中的平衡固溶度公式,并结合Fe2Ti的形成自由能,推导出了钛在铁素体中的平衡固溶度公式。这对于钛的碳化物、氮化物及碳氮化物等第二相颗粒在铁基体中的固溶度积求算以及相关的固溶析出行为等方面的研究具有重要的作用。     

Alloying behavior of Co3Ti

The alloying (substitution) behavior of Ll₂-type Co₃Ti({fx1433-01}) compound was investigated at an isothermal section of 1323 K by the observation of the direction of solubility lobe of Ll₂ phase. The solubility lobes of additions of V, Ta, Cr, W, and Al indicated that they substitute for Ti site, those of Ni and Cu for Co site, and that of Fe for both sites. However, the preferable substitution natures for additions of Zr, Hf, Nb, Mn, and Si, and of Mo and Ge were not determined because of the small solubility limit, and because of no preferable solubility lobe, respectively. The substitution behavior and solubility limit obtained in the ternary Co₃Ti compound were evaluated with the thermo-dynamic concept. The Research Institute for Iron, Steel and Other Metals The Research Institute for Iron, Steel and Other Metals     

Tensile behavior of the L12 compound Al67Ti25Cr8

Temperature-related variations in tensile yield strength and ductility were studied on cast, homogenized and isothermally forged Al₆₇Ti₂₅Cr₈. Yield strength dropped discontinously between 623 K and 773 K and then decreased gradually with increasing temperature. Below 623 K, fracture occurred prior to macroscopic yielding. Ductility decreased from 0.2% at 623 K to zero at 773 K, but increased again at higher temperatures. At 1073 K, an elongation of ∼ 19% was obtainable, and ultimate tensile strength and localized necking were observed. Fracture surfaces and deformed microstructures were examined. The 1073 K tensile specimen that exhibited ∼ 19% elongation showed grain boundary serrations and some evidence of recrystallization (likely dynamic) although fracture occurred predominantly via an intergranular mode.     

Factors affecting the intergranular hydrogen embrittlement of Co3Ti

The influence of intergranular hydrogen embrittlement on the mechanical behavior and fracture behavior of Co₃Ti and 0.1 wt% B-doped Co₃Ti compounds were studied. The significant environmental effect was investigated at ambient temperatures. The elongation and tensile strength showed lower values in the sequence of vacuum, air and hydrogen conditions though the yield strength was insensitive to the environment. The remarkable strain rate dependence was also investigated. As the strain rate decreased, the elongation and tensile strength decreased in a sigmoidal form and again the yield strength remained constant. The decreases of the elongation and tensile strength were investigated with decreasing test temperature below 400°C at the lower strain rate. These embrittlements were severer in the nearstoichiometric alloys of Co-23 at.% Ti than in the off-stoichiometric alloys of Co-21 at.% Ti. The addition of 0.1 wt% B did not actually affect the mechanical behavior of undoped Co₃Ti compounds. Fracture behavior was fairly consistent with the mechanical behavior; there was a change in fracture mode from the transgranular fracture mode, through a mixed mode, to the intergranular fracture mode as the strain rate decreases, by the alternation from vacuum to hydrogen conditions and as the Co atoms become excess. The reduction of ductility and tensile strength occurred in the present Co₃Ti compound was suggested to be due to hydrogen-assisted intergranular embrittlement. The dynamic and atomistic mechanism by which the cohesive strength of grain boundary was affected by the hydrogen was proposed as the probable explanation.     

Solubility and diffusion of hydrogen in vanadium-oxygen alloys

The solubilities and diffusion coefficients of hydrogen have been measured in vanadium-oxygen alloys. A small increase in the isopiestic solubility of hydrogen at 297 and 373 K was caused by the addition of oxygen to vanadium, but Sieverts’ law was obeyed in each alloy in the hydrogen concentration ranges studied. Hydrogen diffusion coefficients as a function of hydrogen concentration were measured at 227, 297, and 373 K by a Boltzmann-Matano method that also allowed a determination of the terminal hydrogen solid solubility. The hydrogen diffusion coefficients decreased with increasing-oxygen concentrations. The solubility and diffusion results do not fit a simple trapping model. The terminal hydrogen solid solubility increased slightly with oxygen concentration     

Solubility of hydrogen in cubic titanium oxycarbides

Conclusions It has been established that hydrogen fills mainly the octahedral voids among the closely packed titanium atoms. Examination of infrared spectra reveals that TiC_xO_yH_u phases exhibit no valence vibrations of OH_n groups.Translated from Poroshkovaya Metallurgiya, No. 12(156), pp. 61–64, December, 1975.     

A novel hydride phase in hydrogen charged Ti3Al

The effect of internal hydrogen on the microstructural modification of Ti₃Al (α₂) compound was studied by large-angle neutron scattering and transmission electron microscopy. Ti-25 at.% Al(Ti₃Al) specimens were exposed to gaseous hydrogen atmosphere at 600°C that resulted in internal hydrogen concentration of 2000 ppm. The hydrogen-charged alloy consisted of a mixture of α₂ phase and a novel Ti₃AlH phase with the E2₁, (Pm3m) crystal structure. The lattice parameters and atomic arrangement of the Ti₃A1H phase were determined.     

Ti3Al对TiCu15Ni15钎料组织的影响

分别以0％，25％，50％，75％，100％比例的Ti3A1替换TiCu15Ni15中Ti，对所得的钎料进行组织形貌及成分分析。研究结果表明：钎料合金由先结晶低Cu，Ni含量相和后结晶的高Cu，Ni含量相组成，随TiaAl增加。低Cu，Ni含量相减少，高Cu，Ni含量相增加，同时由于Nb含量增加，背散射图像发生变化，先结晶相由灰色逐渐变为亮白色，后结晶相成分偏析增加，先结晶高Nb相为灰色，后结晶低Nb相为黑色，至5^#合金形态发生显著变化，灰色相由块团状变为短条或片状，其中央为白色边缘为灰色，这将引起性能变化。     

On the creep behavior of the Ti3Al titanium aluminide Ti25Al10Nb3V1Mo

The temperature and stress dependence of the steady-state creep behavior of the Ti₃Al alloy Ti25Al10Nb3V1Mo (at.%) has been evaluated. Two microstructural conditions were evaluated as follows: As processed (rolled) consisting of the fine grained (approx. 6–10 μm) β plus ordered α₂ phase and beta heat treated consisting of coarse grained (approx. 150 μm) retained ordered B2 phase with a fine Widmanstatten structure within the grain interiors. The steady-state creep behavior of both microstructural conditions was studied over the temperature range of 650–815°C. The apparent creep activation energies and stress exponents were measured for both microstructural conditions. The temperature and stress dependence of the steady-state creep rate of both microstructures can be described well by the power law creep equation suggesting dislocation motion as the operative deformation mechanism. Over the temperature-stress regime of the present study, the creep deformation of the fine grained microstructure possibly breaks down into a low temperature (dislocation core diffusion controlled) regime and a high temperature (bulk diffusion controlled) regime within the power law creep region as indicated by the apparent creep activation energies measured. Upon β heat treatment, creep deformation is found to be governed by a single rate limiting process. At temperatures and stress levels where a direct comparison can be made, the steady-state creep rates of the β heat treated Ti-25-10-3-1 exhibit an order of magnitude decrease over those of the processed material. This suggests the possibility of some mechanism other than power law creep controlling within the regime corresponding to the low apparent activation energy of the fine grained microstructure.     

]Microstructure and hydrogen effects on fracture in the alloy A-286

The commercial iron-base superalloy A-286 was solution-treated and aged at 993 K for times ranging from 0. 5 to 450 hours, including the peak-strength age for 16 hours. Microstructural examination showed that the equilibriumη phase formed first at grain boundaries after about 6 hours of aging and increased in amount with additional aging. Tensile tests on specimens which were uncharged or hydrogen charged from the gas phase revealed in all cases that ductile fracture took place by microvoid coalescence. The path of ductile fracture changed with aging, however, becoming increasingly intergranular with increased aging time after 50 hours. It was found that hydrogen decreased ductility, particularly for aging times greater than 4 hours, although the fracture with hydrogen remained ductile in character. The amount of loss in ductility was approximately constant beyond 4 hours of aging and was independent of fracture path. Fracture was evidently nucleated by carbide inclusion particles by they’ strengthening particles (particularly from 4 to 16 hours of aging) and, at aging times of 50 hours or more, by grain boundaryη phase. These observations were consistent with fractographic observations, including dimple size measurements, and with previous work.     

轧制下线温度对15CrNiMo硬度及析氢行为的影响

为了优化牙轮钻头用15CrNiMo圆钢轧制工艺,降低圆钢氢含量及硬度,减少白点缺陷以及应力开裂的质量风险,对比了不同轧制下线温度对圆钢宏观硬度、显微硬度以及显微组织的影响,并采用升温脱氢分析方法(thermal desorption spectroscopy,简称TDS)对圆钢析氢曲线、氢含量等进行了对比分析。结果显示,升高轧制下线温度可以有效提高钢材铁素体组织比例,从而使钢材整体硬度降低,另外也有助于减少钢中的氢含量。     

The influence of residual hydrogen and moisture-released hydrogen on the embrittlement of Ni3(Al,Ti) single crystals

The influence of residual hydrogen and hydrogen released from environment on the embrittlement of the Ni₃(Al,Ti) single crystals with [001] orientation was investigated by the tensile tests at a room temperature both in air and vacuum, using specimens containing residual hydrogen in a wide range of contents (0.6–70 massppm). The tensile elongation and the UTS values of specimens deformed in air were primarily insensitive to the residual hydrogen contents, and the associated fractography exhibited the brittle fracture mode along the [001] plane. On the other hand, the tensile elongation and the UTS values of specimens deformed in vacuum were strongly sensitive to the residual hydrogen contents. With decreasing the residual hydrogen content, the tensile elongation and the UTS values increased, and the associated fractography changed from the brittle manner to the ductile manner. These results indicate that the ductility of the Ni₃(Al,Ti) single crystals deformed in air is controlled by hydrogen released from moisture in air while that of the Ni₃(Al,Ti) single crystals deformed in vacuum is controlled by residual hydrogen.