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The combined effects of alloying additions and heat treatment on the evolution and development of the microstructures of Fe3Al-based Fe−Al−Cr−C alloys produced by melt suction processing have been examined. Particular emphasis has been placed on
the distribution and morphology of carbides in rapidly solidified Fe3Al-based intermetallics. The results suggest that the formation of intrinsically hard and brittle Fe3AlC and Cr7C3 type carbides depends on the alloying content. These carbides tend to form preferentially along the grain boundaries where
more continuous and coarse networks are observed, especially for alloys having higher Cr and C content. These networks are
fragmented as a result of heat treatment at 1200 °C and subsequent air cooling and quenching. 相似文献
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Metal Science and Heat Treatment - 相似文献
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Seung Eon Kim Hi Won Jeong Yong Taek Hyun Yong Tai Lee Chan Hoi Jung Soon Kook Kim Jae Sung Song Jun Hee Lee 《Metals and Materials International》2007,13(2):145-149
The effect of niobium and tantalum on the elastic modulus and the in vitro biocompatibility in binary titanium alloys was
studied. The Young's modulus of titanium was effectively lowered with additions of Nb or Ta, depending significantly upon
the microstructure. Martensitic microstructures such as α' and α" decreased the elastic modulus, while the ω phase increased
it. Ti−10%Nb, Ti−30%Nb and Ti−30%Ta alloys exhibited very low elastic moduli of 74, 80, and 58 GPa, respectively. The corrosion
resistance of Ti−xTa was slightly higher than that of Ti−xNb, which was comparable to that of CP Ti or Ti−6A−4V. No ion release
was detected in Hank's solution, while Ti ions were released in 0.1% lactic acid ranging from 0.03 to 0.11 μg/ml for both
the Ti−xNb and Ti−xTa alloys. MG63 osteoblast-like cell proliferation on Ti−30%Ta was less active compared with Ti−30%Nb,
CP Ti or Ti−6Al−4V. 相似文献
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The correlation between the oxide impedance and corrosion behavior of two series of Zr−Nb−Sn−Fe−Cu alloys was evaluated. Corrosion
tests were performed in a 70 ppm LiOH aqueous solution at 360°C for 300 days. The results of the corrosion tests revealed
that the corrosion behavior of the alloys depended on the Nb and Sn content. The impedance characteristics for the pre- and
post-transition oxide layers formed on the surface of the alloys were investigated in sulfuric acid at room temperature. From
the results, a pertinent equivalent circuit model was preferably established, explaining the properties of double oxide layers.
The impedance of the oxide layers correlated with the corrosion behavior; better corrosion resistance always showed higher
electric resistance for the inner layers. It is thus concluded that a pertinent equivalent circuit model would be useful for
evaluating the long-term corrosion behavior of Zr−Nb−Sn−Fe−Cu alloys. 相似文献
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Metal Science and Heat Treatment - 相似文献
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《中国有色金属学会会刊》2019,29(10):2117-2127
To clarify phase transformation evolution of Nb-doped Ni−Mn−Ga bulk alloys after aging and ball milling, the microstructure and phase transformation of the aged and ball-milled dual-phase Nb-doped Ni−Mn−Ga alloys were investigated by SEM, EDS, XRD, DSC and susceptibility measurements. The as-cast alloys were mainly composed of the second phase with layer-shape and presented a reduced martensitic transformation with increasing the second phase content. The second phase transformed from layer-shape to dense bar-shape and the martensitic transformation was enhanced after being quenched at 1173 K. After aging at 673 and 873 K, the 3% Nb alloy with less second phase exhibited a single-step phase transformation, whereas the 6% Nb and 9% Nb alloys with more second phase exhibited a two-step martensitic transformation and Curie transition. The martensitic transformation and Curie transition of the as-milled dual-phase particles disappeared and were retrieved after annealing at 1073 K due to the recovery of high ordered structure of the matrix. 相似文献
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《中国有色金属学会会刊》2021,31(11):3328-3341
In order to simultaneously improve strength and formability, an analytical model for the concentration distribution of precipitates and solute elements is established and used to theoretically design and control the heterogeneous microstructure of Al−Zn−Mg−Cu alloys. The results show that the dissolution of precipitates is mainly affected by particle size and heat treatment temperature, the heterogeneous distribution level of solute elements diffused in the alloy matrix mainly depends on the grain size, while the heat treatment temperature only has an obvious effect on the concentration distribution in the larger grains, and the experimental results of Al−Zn−Mg−Cu alloy are in good agreement with the theoretical model predictions of precipitates and solute element concentration distribution. Controlling the concentration distribution of precipitates and solute elements in Al−Zn−Mg−Cu alloys is the premise of accurately constructing heterogeneous microstructure in micro-domains, which can be used to significantly improve the formability of Al−Zn−Mg−Cu alloys with a heterostructure. 相似文献
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Xiao-ping LIN Yang KUO Lin WANG Jie YE Chong ZHANG Li WANG Kun-yu GUO 《中国有色金属学会会刊》2021,31(6):1587-1598
Mg?Zn?Cu?Zr?Ca samples were solidified under high pressures of 2–6 GPa. Scanning electron microscopy and electron backscatter diffraction were used to study the distribution of Ca in the microstructure and its effect on the solidification structure. The mechanical properties of the samples were investigated through compression tests. The results show that Ca is mostly dissolved in the matrix and the Mg2Ca phase is formed under high pressure, but it is mainly segregated among dendrites under atmospheric pressure. The Mg2Ca particles are effective heterogeneous nuclei of α-Mg crystals, which significantly increases the number of crystal nuclei and refines the solidification structure of the alloy, with the grain size reduced to 22 μm at 6 GPa. As no Ca segregating among the dendrites exists, more Zn is dissolved in the matrix. Consequently, the intergranular second phase changes from MgZn with a higher Zn/Mg ratio to Mg7Zn3 with a lower Zn/Mg ratio. The volume fraction of the intergranular second phase also increases to 22%. Owing to the combined strengthening of grain refinement, solid solution, and dispersion, the compression strength of the Mg–Zn–Cu–Zr–Ca alloy solidified under 6 GPa is up to 520 MPa. 相似文献
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Six Mg−Zn−Zr alloys, with and without RE additionswere tested at room temperature and 473 K. Yield stresses of parts of the
six alloys were calculated theoretically. Microstructures of the specimens before and after heat treatment were compared in
order to determine the reason for the decrease in yield stresses at room temperature. The strengthening mechanisms at different
temperatures were discussed.
This article is based on a presentation in “The 7th Korea-China Workshop on Advanced Materials” organized by the Korea-China
Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju
Hotel, Jeju Island, Korea on August 24–27, 2003. 相似文献
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《中国有色金属学会会刊》2020,30(6):1429-1438
The effects of minor Sc and Zr additions on the mechanical properties and microstructure evolution of Al−Zn−Mg−Cu alloys were studied using tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ultimate tensile strength of the peak-aged Al−Zn−Mg−Cu alloy is improved by about 105 MPa with the addition of 0.10% Zr. An increase of about 133 MPa is observed with the joint addition of 0.07% Sc and 0.07% Zr. For the alloys modified with the minor addition of Sc and Zr (0.14%), the main strengthening mechanisms of minor addition of Sc and Zr are fine-grain strengthening, sub-structure strengthening and the Orowan strengthening mechanism produced by the Al3(Sc,Zr) and Al3Zr dispersoids. The volume of Al3Zr particles is less than that of Al3(Sc,Zr) particles, but the distribution of Al3(Sc,Zr) particles is more dispersed throughout the matrix leading to pinning the dislocations motion and restraining the recrystallization more effectively. 相似文献
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《中国有色金属学会会刊》2020,30(9):2326-2338
The microstructure and mechanical properties at different depths of squeeze-cast, solution-treated and aged Al−5.0Mg−3.0Zn−1.0Cu alloy were investigated. For squeeze-cast alloy, from casting surface to interior, the grain size of α(Al) matrix and width of T-Mg32(AlZnCu)49 phase increase significantly, while the volume fraction of T phase decreases. The related mechanical properties including ultimate tensile strength (UTS) and elongation decrease from 243.7 MPa and 2.3% to 217.9 MPa and 1.4%, respectively. After solution treatment at 470 °C for 36 h, T phase is dissolved into matrix, and the grain size increases so that the UTS and elongation from surface to interior are respectively reduced from 387.8 MPa and 18.6% to 348.9 MPa and 13.9%. After further peak-aging at 120 °C for 24 h, numerous G.P. II zone and η′ phase precipitate in matrix. Consequently, UTS values of the surface and interior increase to 449.5 and 421.4 MPa, while elongation values decrease to 12.5% and 8.1%, respectively. 相似文献
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《中国有色金属学会会刊》2020,30(8):2143-2155
The influence of brazing temperature and brazing time on the microstructure and shear strength of γ-TiAl/GH536 joints brazed with Ti−Zr−Cu−Ni−Fe−Co−Mo filler was investigated using SEM, EDS, XRD and universal testing machine. Results show that all the brazed joints mainly consist of four reaction layers regardless of the brazing temperature and brazing time. The thickness of the brazed seam and the average shear strength of the joint increase firstly and then decrease with brazing temperature in the range of 1090−1170 °C and brazing time varying from 0 to 20 min. The maximum shear strength of 262 MPa is obtained at 1150 °C for 10 min. The brittle Al3NiTi2 and TiNi3 intermetallics are the main controlling factors for the crack generation and deterioration of joint strength. The fracture surface is characterized as typical cleavage fracture and it mainly consists of massive brittle Al3NiTi2 intermetallics. 相似文献
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《中国有色金属学会会刊》2019,29(10):2047-2055
The morphology and crystal structure of the precipitates in Mg−7Gd−3Y−1Nd−1Zn−0.5Zr alloy during isothermal ageing at 240 °C were investigated using transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). After under-ageing for 2 h, the precipitates in the alloy are ordered solute clusters with rare earth atomic columns exhibiting hexagonal ring structure, zigzag GP zones and β' in its early formation. After peak-ageing for 18 h, the precipitates are mainly β' and new rod-like β'p accompanied with β'. After over-ageing for 100 h, the precipitates are β', β1, long-period stacking ordered (LPSO) building block known as γ′ and 14H-LPSO. β' has the three-dimensional shape of convex lens with smaller length-to-width ratio viewed along 〈0001〉α than that in the EW75 alloy. The excellent thermal stability of this alloy can be attributed to the γ' and 14H-LPSO retarding the growth of β' and β1, low diffusion rate of rare earth atoms and physical character of β' and β1. 相似文献
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Evaluations of austenite fraction and transformation kinetics upon intercritical annealing of low carbon TRIP steels were
attempted using quantitative dilatometric analysis. The measured dilation curves were analyzed by taking the carbon distribution
between austenite and its decomposed phases into account. The amount of austenite formed during intercritical annealing and
its carbon content obtained by dilatometric measurement was compared with the values predicted by thermodynamic calculations
under the ortho-equilibrium and para-equilibrium conditions. The kinetics of the reaustenization process including pearlite
dissolution and non-isothermal and isothermal formation of austenite could be quantitatively characterized by means of a modified
JMAK (Johnson-Mehl-Avrami-Kolmogrov) equation. 相似文献