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1.
FeCrNiCoBx high-entropy alloy coatings were prepared by laser cladding, and the effects of boron addition on the microstructure, hardness and corrosion resistance of the coatings were studied. Results showed that the coatings comprised a simple FCC solid solution with boride precipitation. When 0.5?≤?x?≤?1.0, (Cr, Fe)2B with an orthorhombic structure was found in the coatings, and the hardness and corrosion resistance of the coatings were enhanced by increasing boron content. As x approached 1.25, the borides changed from orthorhombic (Cr, Fe)2B to tetragonal (Fe, Cr)2B, which deteriorated the corrosion resistance of the coatings. Stacking faults found in (Cr, Fe)2B may be caused by the phase transformation of borides. 相似文献
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为改善激光熔化沉积TC31高温钛合金力学性能,本文通过光学显微镜、SEM、TEM和力学性能测试的方法研究了退火温度对合金中组织演化行为的影响,及其与合金室温和650 ℃高温力学性能的关系。结果表明:组织中初生α相含量随着退火温度升高而降低,其溶解主要发生在950 ℃以上,980 ℃退火后含量仅为29%。当退火温度超过930 ℃时,初生α相片层宽度明显增加。随着退火温度升高,α/β界面处析出的(Ti, Zr)6Si3相尺寸增加,且进入α相片层内部。合金在800~1 000 ℃退火时,合金室温拉伸屈服强度随退火温度升高趋于降低。受相界面析出的硅化物聚合长大及α相片层尺寸增加等因素影响,合金高温屈服强度随退火温度升高先降低后增加。合金经过1 000 ℃退火后,呈现良好的高温性能,其650 ℃下抗拉强度达657 MPa、屈服强度约为466 MPa、延伸率27%。 相似文献
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Microstructure and mechanical properties of a new β high strength Ti–3.5Al–5Mo–6V–3Cr–2Sn–0.5Fe titanium alloy were investigated in this paper. Both the α/β and β solution treatment and subsequent aging at temperatures ranging from 440 °C to 560 °C for 8 h were introduced to investigate the relationship between microstructures and properties. Microstructure observation of α/β solution treatment plus aging condition shows that the grain size is only few microns due to the pinning effect of primary α phase. The β solution treatment leads to coarser β grain size and the least stable matrix. The size and volume fraction of secondary α are very sensitive to temperature and strongly affected the strength of the alloy. When solution treated at 775 °C plus aged at 440 °C, the smallest size (0.028 μm in width) of secondary α and greatest volume fraction (61%) of α resulted in the highest yield strength (1624 MPa). And the yield strength decreased by an average of 103 MPa with every increase of 40 °C due to the increase of volume fraction and decrease of the size of secondary α. In β solution treatment plus aging condition, tensile results shows that the strength if the alloy dramatically decreased by an average of 143 MPa for every increase of 40 °C because of larger size of secondary α phase than α/β solution treated plus aged condition. 相似文献
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Microstructure and mechanical properties of nanostructure multilayer CrN/Cr coatings on titanium alloy 总被引:1,自引:0,他引:1
Piotr Wiecinski Jerzy SmolikHalina Garbacz Krzysztof J. Kurzydlowski 《Thin solid films》2011,519(12):4069-4073
Five different nanostructured, multilayer coatings (CrN/Cr)x8 with different thickness ratio of Cr and CrN layers were deposited by PAPVD (Plasma Assisted Physical Vapour Deposition) vacuum arc method on Ti6Al4V titanium alloy. The microstructure, chemical and phase composition of the CrN and Cr sub-layers were characterized by SEM with EDX and Cs-corrected dedicated STEM on cross-sections prepared by focus ion beam. Besides, hardness and Young's modulus of the (Cr/CrN)x8 coatings has been measured. The adhesion has been tested by scratch test method. The obtained (CrN/Cr) multilayer coatings, 5-6 μm in thickness, have homogeneous and nanocrystalline structure, free of pores and cracks. The microstructures of Cr and CrN layers consist of columnar grains below 100 nm in diameter. The hardness and Young's modulus of these coatings depend linearly on thickness ratio of Cr and CrN layers. The decrease of the thickness ratio Cr/CrN 0.81 to 0.15 results in the increase of hardness from 1275 HV to 1710 HV and Young's modulus from 260 GPa to 271 GPa. 相似文献
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《Materials Science & Technology》2013,29(11):987-993
AbstractSuperplastic forming is particularly attractive for high temperature Ti alloys because of the much lower forming stresses compared with those encountered during forging. The superplastic deformation parameters of IMI 834 sheet were obtained at 900, 940, and 990°C. At 990°C, IMI 834 shows low flow stresses, high values of strain rate sensitivity, and minimum strain anisotropy, however, 300% superplastic elongation was readily obtained at the lower forming temperature of 940°C but with a higher flow stress. A reduction in the room temperature and 600°C tensile properties with superplastic strain resulted from strain enhanced grain growth during superplastic deformation; this effect was greatest at 990°C. Aging of post 990°C superplastically formed material was studied. The creep performance of IMI 834 was found to be slightly reduced by superplastic forming. These properties and the changes in the microstructure and texture are compared with other Ti alloys under superplastic conditions.MST/1822 相似文献
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Effects of substrate temperature and post-annealing on microstructure and properties of (AlCrNbSiTiV)N coatings 总被引:1,自引:0,他引:1
AlCrNbSiTiV nitride films were deposited by reactive radio-frequency magnetron sputtering from an AlCrNbSiTiV equimolar target. Effects of substrate temperatures from 100 °C to 500 °C and post-annealing on the chemical composition, microstructure and mechanical properties of the films were investigated. Experimental results indicate that all nitride films have a single face-centered cubic (NaCl-type) structure with the stoichiometric nitride ratio approximately as Al8Cr8Nb7Si9Ti9V8N50. Increasing the substrate temperature increases the grain size and the compressive residual stress, but decreases the lattice constant. The highest hardness of (AlCrNbSiTiV)N nitride films is 41 GPa, corresponding to the super-hard grade. Even annealing in a vacuum at 900 °C for 5 h caused no notable change in the crystalline structure, lattice parameter, grain size or hardness. The super-hard level and thermal stability of these multi-component coatings are discussed. 相似文献
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Ultrasonic treatment was applied during solidification forming of 6016 aluminium alloys. The effects of ultrasonic vibration on the microstructure and mechanical properties of the 6016 aluminium alloy ingot were studied. Compared with conventional casting, the ingot prepared with ultrasound applied to the molten metal had a fully refined microstructure and greater material homogeneity. Ultrasonic treatment reduced the amount of porosity developed by embedded gas and also resulted in an obvious decrease in solidification defects, like shrinkage. In addition, component segregation was minimised and the mechanical properties were enhanced. 相似文献
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Tomohiro Ando Koichi Nakashima Toshihiro Tsuchiyama Setsuo Takaki 《Materials Science and Engineering: A》2008,486(1-2):228-234
High nitrogen titanium alloy with the chemical composition of Ti–4%Cr–0.6%N was produced by solution nitriding to nitrogen-free Ti–4%Cr alloy, and then its microstructure was controlled to have fine (α + β) dual phase structure by aging treatment to improve the ductility. As solution-nitrided specimen has a platelet hcp-martensitic structure (α′) and is characterized by hard but brittle nature that has been produced by solid solution of 0.6% of nitrogen. On the following aging treatment, fine β phase formed along the original plate boundaries, resulting in a fine (α + β) dual phase microstructure. X-ray and EELS analyses revealed that nitrogen is greatly concentrated in the tempered α′ phase. Although the hardness of as-quenched material gradually decreases during the aging treatment with increasing volume fraction of β, the hardness can be kept much higher than that of the aged Ti–4%Cr alloy without nitrogen. As a result of tensile testing, it was found that the aged Ti–4%Cr–0.6%N alloy has high tensile strength over 1 GPa with moderate ductility. 相似文献
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采用Ti、Ni纯元素混合粉末真空烧结技术制备了孔隙分布均匀且力学性能优良的多孔TiNi形状记忆合金(SMA),并利用X射线衍射仪、金相显微镜、扫描电子显微镜及电子万能试验机研究对比了900、950、1000、1050、1100和1150℃6个不同烧结温度对合金微观结构和力学性能等的影响。结果表明,烧结温度是影响多孔TiNi合金性能的决定性因素,通过调节烧结温度可有效调节合金的相组成、孔隙特征和力学性能。随着烧结温度的升高,合金的次生相逐渐减少,相组成成分更加均一;致密度不断提高,由59%上升到62%,孔隙分布愈加均匀且孔隙形貌由多尖角形趋于球形化;抗拉强度由72.43MPa增加到160.12MPa,弹性模量从1.08GPa增加到1.32GPa。 相似文献
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The effects of the rheocasting process and T5 heat treatment on microstructure and mechanical properties of A356 alloy were investigated. The results show that the temperature range for the solid-liquid state is roughly between 560 °C and 630 °C, and the solid fraction increases from 0% to 100% with decreasing temperature. The finer microstructure in rheocasting in comparison with the one in conventional casting was attributed to pressure breaking down the secondary dendrite arms, especially for specimens around 600-610 °C. It was proved that rheocasting specimens have improved mechanical properties over the conventional casting ones. Furthermore, the result shows that T5 heat treatment can strengthen A356 alloy, while the plasticity was reduced at the same time. 相似文献
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采用异步轧制、多向异步轧制、高温异步轧制、高温多向异步轧制四种不同的方式轧制双相镁锂合金板材。通过光学显微镜、MTS E43拉伸试验机和X射线衍射仪观察不同工艺轧制后合金的显微组织、力学性能以及织构特征,综合分析温度和轧制方向条件耦合对镁锂合金组织和力学性能的影响。结果表明:四种轧制工艺可以使α-Mg相沿轧制方向伸长,同时沿着轧制方向法向细化。高温多向异步轧制后α相厚度最低为2.6μm。多向异步轧制后材料的屈服强度、抗拉强度、伸长率分别为149,167 MPa,14.5%,其综合力学性能最优。多向轧制使双峰织构沿ND方向45°偏转,高温轧制使双峰织构由基极向RD方向偏转的角度降低。轧制后样品R-cube织构组分最强,高温多向异步轧制使β-Li相轧制织构转变成为{001}〈100〉织构,有利于{011}〈111〉滑移系发生多滑移。 相似文献
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《Thin solid films》2006,494(1-2):173-178
Polycrystalline CrN/AlN multilayer coatings were deposited by RF magnetron sputtering on silicon (001) substrates. The bilayer periods of CrN/AlN were controlled from 4 nm to 20 nm by the use of shutters, which were adjusted by a programmable logic control (PLC). To evaluate the thermal stability, the films were annealed at 500 °C, 600 °C, 700 °C, 800 °C, and 850 °C, for 1 h in both vacuum and air environments. The phase transformation during thermal evolution was studied by X-ray diffraction (XRD). The microstructure of CrN/AlN multilayer coatings as-deposited and after annealing was observed by transmission electron microscopy (TEM). The hardness of as-deposited CrN/AlN coating with a period of 4 nm was 28.2 GPa, which was 60% higher than that predicted by the rule of mixtures. The hardness of CrN/AlN multilayer coatings annealed at 850 °C in vacuum remained similar to the as-deposited state, and the nano-layered structure still persisted. The thermal stability of CrN/AlN coatings was better than that of CrN coating. The hardness degradation ratio of CrN/AlN coating with modulation period of 4 nm was only 8.1% at 700 °C, which was superior to that of a simple CrN coating. 相似文献
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Microstructure evolution of the extruded AZ80 magnesium alloy and different precipitation behavior of β-Mg17Al12 phase in different heat treatment conditions were investigated. Solution treatment caused the dissolution of β-Mg17Al12 phase and the grain coarsening. During aging, discontinuous precipitates were preferentially initiated at some of the grain boundaries and then continuous precipitates appeared in the grain interiors. In the period of direct-aging, discontinuous precipitates formed between the banded structure and no continuous precipitate appeared. After solution and aging treatment, an improved combination of strength and elongation was obtained. The highest strength was achieved for the extruded AZ80 sample after directing-aging treatment. 相似文献
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为寻求优化钛合金组织和力学性能的新思路,本文采用电冲击处理方法对TC11钛合金进行组织结构调控,并利用SEM和EBSD对处理前后材料的微结构、相含量和织构分布进行表征分析,同时利用处理前后的硬度分布和压缩性能分析来体现力学性能变化。微结构研究表明,当电冲击处理时间增加至0.04 s,材料发生针状二次α向β相转变,β相含量从10.1%增加到14.4%,且初生α/β相界面平滑度增加,主要归因于电冲击处理过程的热效应和非热效应。织构研究表明,电冲击处理0.04 s后,α相织构强度从6.77增大到10.53,β相织构强度增加不明显,α相和β相织构变化与电冲击处理能量集中引起的相变有关。力学性能研究结果显示,电冲击处理0.06 s后,显微硬度和屈服强度明显提高,主要原因是样品内部析出大量细小的针状马氏体α相,起到弥散强化作用。综上,利用电冲击处理来调控钛合金微结构将是一种新的探索,可为钛合金力学性能改善提供一条新途径。 相似文献
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M. Shaat 《Materials Science & Technology》2018,34(10):1149-1167
This review presents an investigation on effects of the processing conditions on the microstructural evolution and mechanical properties of commercial pure titanium processed by Equal Channel Angular Pressing (ECAP). An overview of ECAP processing is presented. A discussion on the microstructure evolution of ECAPed titanium emphasising effects of the ECAP-route type, processing temperature, number of ECAP passes, and mechanical/thermal treatments is presented. Moreover, the variations of the mechanical properties (yield strength, tensile strength, and ductility) of titanium as functions of the grain size are reported for the different conditions of ECAP processing. In addition, the best estimates of the Hall–Petch parameters for titanium processed by ECAP, ECAP followed by mechanical and/or thermal annealing are reported. 相似文献
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Aluminium alloy (6063) was severely rolled upto 92% thickness reduction at liquid nitrogen temperature and room temperature to study the effect of rolling temperature on its mechanical properties and microstructural characteristics by using tensile tests and SEM/electron back scattered diffraction (EBSD), transmission electron microscope (TEM), DSC, X-ray diffraction (XRD) as compared to room temperature rolled (RTR) material with the same deformation strain. An improved strength (257 MPa) of cryorolled 6063 Al alloy was observed as compared to the room temperature rolled alloy (232 MPa). The improved strength of cryorolled alloy is due to the accumulation of higher dislocation density than the room temperature rolled material. The tensile properties of cryorolled alloy and the alloy subjected to different annealing treatments were measured. The cryorolled alloy subjected to annealing treatment at 300 °C for 5 min exhibits an ultrafine-grained (UFG) microstructure with improved tensile strength and ductility. 相似文献