A Comparative Study of the γ/γ′ Eutectic Evolution During the Solidification of Ni-Base Superalloys

The evolution of γ/γ′ eutectic during the solidification of Ni-base superalloys CMSX-10 and CMSX-4 was investigated over a wide range of cooling rates. The microsegregation behavior during solidification was also quantitatively examined to clarify the influence of elemental segregation on the evolution of γ/γ′ eutectic. In the cooling rate ranges investigated (0.9 to 138.4 K/min (0.9 to 138.4 °C/min)), the γ/γ′ eutectic fraction in CMSX-10 was found to be more than 2 times higher than that in CMSX-4 at a given cooling rate. However, the dependence of the γ/γ′ eutectic fraction on the cooling rate in both alloys showed a similar tendency; i.e., the γ/γ′ eutectic fraction increased with increasing the cooling rate and then exhibited a maximum plateau at and above the certain critical cooling rate in both alloys. This critical cooling rate was found to be dependent on the alloy composition and was estimated to be about 12 K/min (12 °C/min) and 25 K/min (25 °C/min) for CMSX-10 and CMSX-4, respectively. The calculated solid compositions based on the modified Scheil model revealed that even a small compositional difference of total γ′ forming elements in the initial composition of the alloy can play a significant role in the as-cast eutectic fraction during the solidification of Ni-base superalloys. The evolution of the γ/γ′ eutectic fraction with respect to the cooling rate could be rationalized by taking into account the effects of back-diffusion in solid and dendrite arm coarsening on decreasing the extent of microsegregation.     

Application of binary interdiffusion models to γ′(Ni3Al)/γ(Ni) diffusion bonded interfaces

Nickel and Ni₃Al platelets have been joined by diffusion solid state bonding with two different sets of bonding parameters (applied pressure, temperature, duration). The γ/γ′ interfaces obtained are examined and the transverse concentration profiles are determined. The application of the classical binary interdiffusion models to this particular case is discussed, with increasingly refined hypotheses. A step-by-step numerical calculation procedure is finally proposed which is able to account correctly for the measured profiles at the highest annealing temperature (1100°C). To apply this procedure an experimental determination of the interdiffusion coefficients of Al in the phases γ and γ′ as functions of the local concentration was made according to Matano's method.     

Fe-Cr-Mn(W,V)合金中层错和fcc(γ)→hcp(ε)转变特征

利用TEM和X射线衍射仪对固溶态、固溶空冷态和固溶冰水淬火态亚稳奥氏体Fe-12Cr-10Mn(W,V)合金(84),以及固溶态、固溶+拉伸变形态稳定奥氏体Fe-13Cr-17Mn(W,V)合金(85N)中γ→ε转变与层错之间的关系进行了研究,并对影响γ→ε马氏体转变的合金元素进行了分析,提出了进一步提高合金相稳定性的措施。     

The Influence of Slip Character on the Creep and Fatigue Fracture of an α Ti-Al Alloy

The mechanical performance of engineering titanium alloys has long been known to be sensitive to the nature of applied load waveform. Sustained load hold periods imposed during the fatigue loading of two-phase α + β alloys are detrimental to material performance. A number of factors, particularly material texture, phase morphologies, and slip behavior, are thought to affect the dwell fatigue responses of these materials. This study examines the roles of slip character and applied load waveform on an alloy with a simpler microstructure than the two-phase alloys studied previously. It is found that planar slip has significant influence over the dwell, fatigue, and fracture behaviors of equiaxed-grained, single-phase α Ti-7 wt pct Al.     

w(MgO)/w(Al2O3)对复合炉料熔滴性能的影响

 高炉炉料中适宜的w(MgO)/w(Al₂O₃)可以提高炉渣的冶金性能,有利于高炉的冶炼,以达到增产、节能和降耗的目的。为探究MgO质量分数对复合炉料性能的影响,在试验过程中分别改变复合炉料内烧结矿、球团矿的w(MgO)/w(Al₂O₃),使用高温熔滴炉检测其熔滴性能,并对未滴落物进行XRD、SEM-EDS检测,探究渣中成分和分布规律,最终得到合理的MgO配分结构。试验结果表明,烧结矿中w(MgO)/w(Al₂O₃)由0.8增加至1.2的过程中,滴落温度先减小后增大,软熔带位置不断下移并呈现先变窄后变宽的趋势,镁硅钙石和镁黄长石的含量不断增大,而尖晶石和方镁石含量在w(MgO)/w(Al₂O₃)超过1.0后逐渐增大;球团矿中w(MgO)/w(Al₂O₃)由1.39增加至2.09的过程中,熔化区间先减小后增大,软熔带先上移后下降。烧结矿中w(MgO)/w(Al₂O₃)为1.0、球团矿中w(MgO)/w(Al₂O₃)为1.74时,熔滴特征值为95.55 kPa·℃,复合炉料熔滴性能最佳,有利于高炉顺行。     

原位自生 (Cr,Fe)7C3/Fe3Al复合材料组织结构及物相组成的研究

本文通过真空雾化方法制备原位自生(Cr,Fe)_7C_3/Fe_3Al粉末,采用显微硬度,SEM,TEM,XRD等分析方法对制品的成分,表面形貌,物相组成,及硬度等进行初步分析。研究结果表明,(Cr,Fe)_7C_3/Fe_3Al粉末硬度较Fe3Al粉末有明显提高,同时急速冷却状态下,Fe_3Al粉末与(Cr,Fe)_7C_3/Fe_3Al粉末中基体相皆由DO_3型有序相Fe_3Al组成,Cr以固溶方式存在于基体中。(Cr,Fe)_7C_3以类珠光体团簇状均匀弥散分布在基体之中,碳化物保持Cr_7C_3点阵类型,Fe原子固溶在其中。     

永磁材料R1-δ(2T)δT5型化合物[(R=稀土元素,T=Fe,Co,Ti,V,等过渡金属元素),(δ=2/5,1/2)]的结构和磁性

总结了稀土金属(R)与过渡金属(T)化合物RT₅型系列衍生物中R₃(Fe,M)₂₉和R(Fe,M)₁₂的结构和内禀磁性,以及它们之间的关系.阐述了稳定元素(M)和嵌入轻原子(N,C,H)对其结构和内禀磁性的影响。     

Influence of magnesium on electrochemical properties of RE3-xMgx(Ni0.7Co0.2Mn0.1)9（x=0.5-1.25） alloy electrodes

RE3-xMgx(Ni0.7Co0.2Mn0.1)9 (x=0.5-1.25) alloys were prepared by induction melting and the influence of the partial substitution of RE (where RE stands for La-rich mischmetal) by Mg on the hydrogen storage and electrochemical properties of the alloys were investigated systematically. These alloys mainly consisted of three phases, La(Ni,Mn,Co)5 phase, La2Ni7 phase and Mg2Ni phase. The P-C-T isotherms showed that with Mg content increasing in the alloys, the hydrogen storage capacity first increased and reached the maximum capacity of 1.36 wt.% when x=1.0, and then decreased with x increasing further. Electrochemical studies revealed that the discharge capacity reached the maximum value of 380 mAh/g and the alloy electrode presented better cyclic stability when RE/Mg=2. The high rate discharge ability of the alloy electrodes was also improved by the substitution of Mg for RE. The RE2Mg(Ni0.7Co0.2Mn0.1)9 alloy exhibited better hydrogen absorption kinetics (x=1.0).)     

Studies of Orientations of β″ Precipitates in Al-Mg-Si-(Cu) Alloys by Electron Diffraction and Transition Matrix Analysis

Transition matrix, combine with high-resolution transmission electron microscopy (HRTEM) and stereographic projection, was used in this article to predict and characterize the orientations and electron diffraction patterns of β″ precipitates in Al-Mg-Si-(Cu) alloys. It was found that the β″ phases as the main strengthening precipitates had 12 variants with Al matrix, and the orientation relationships could be expressed as (010) _β″//{100}_Al, [001] _β″//〈310〉_Al, and [100] _β″//〈230〉_Al. Further, based on the C-centered monoclinic structure of β″ precipitate, a new diffraction patterns model under the [001]_Al zone axis could be established, which was in good agreement with the experiment date. Further, it could be used to explain reasonably some issues (for example, the “cross-shaped” diffraction streaks phenomenon). Simultaneously, we also found that the β″ precipitates had only three different zone axes, [010] _β″, [304] _β″, and [ [`1]06 ]_b^￠￠ , left[ {bar{1}06} right]_{{beta^{prime prime } }} , parallel to the [001]_Al direction when they were precipitated from the Al matrix, and the β″ precipitate might deviate 1.6 deg from its original orientation because of the lattice relaxation.     

On the Precipitation-Strengthening Contribution of the Ta-Containing Co3(Al,W)-Phase to the Creep Properties of γ/γ′ Cobalt-Base Superalloys

Metallurgical and Materials Transactions A - The creep strength of single-crystalline Co-based superalloys was found to be comparable to first-generation Ni-base superalloys. However, considerable...     

Preparation of Ce2Fe17N3-δ@FePO4 composite with excellent microwave absorption performance by reduction-diffusion(R/D) and phosphating processes

Ce₂Fe₁₇N_3-δ composites have always been focused on electromagnetic wave(EMW) absorbing field because of their high resonance frequency and magnetic loss.However,the issues of preparation cost and impedance mismatching still limit the industrial conversion and practical application of Ce₂Fe₁₇N_3-δ composites.In this work,the composites of Ce₂Fe₁₇N_3-δ with a phosphate insulation layer(Ce₂Fe...     

Study on preparation and gas sensing property of water-soluble polyaniline/SmBaCuMO_(5+δ)(M=Fe,Co, Ni) for NH_3

Water-soluble polyaniline(PANI), prepared by chemical-oxide and SmBaCuMO5+δ(M=Fe, Co, Ni)(SBCM) powders, prepared by sol-gel method were analyzed through Fourier transform infrared spectroscopy(FT-IR) spectra, X-ray diffraction(XRD), transmission electron microscopy(TEM) and energy dispersive spectroscopy(EDS) respectively, so as to investigate the gas sensitivities of PANI/SmBaCuFeO5+δ(SBCF) and its sensitivity to NH3 under room temperature. The results showed that all of SBCM powders were of double-perovskite structure and PANI was successfully obtained. Under the same condition, the gas sensor based on PANI/SmBaCuFeO5+δ(SBCF) material exhibited higher resistance sensitivity, better selectivity and shorter response-recovery time than others. The resistance sensitivities to NH3 increased with the increasing of atom radius of M in PANI/SBCM.     

Nucleation and epitaxy growth of high-entropy REBa2Cu3O7-δ(RE=Y,Dy,Gd,Sm,Eu)thin films by metal organic deposition

High-entropy REBa₂Cu₃O_7-δ(RE=Y_0.7+Dy_0.2+Gd_0.2+Sm_0.2+Eu_0.2)(HE-REBCO) superconducting films doped with multiple rare earth elements were successfully fabricated with thickness up to 800 nm by a trifluoroacetate-metal organic deposition(TFA-MOD).The enhanced entropy change ΔS of the HEREBCO system promotes the c-axis growth of REBCO thin film in the competition with a/b-axis growth.The microstructure and elemen...