scholarly journals Passive Film Properties of Bimodal Grain Size AA7075 Aluminium Alloy Prepared by Spark Plasma Sintering

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3236
Author(s):  
Wenming Tian ◽  
Zhonglei Li ◽  
HuiFeng Kang ◽  
Fasong Cheng ◽  
Fangfang Chen ◽  
...  
Keyword(s):  
Passive Film ◽  
Aluminium Alloys ◽  
Defect Density ◽  
Intermetallic Phases ◽  
Coarse Grain ◽  
Fine Grain ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Sintered Alloys ◽  
Bimodal Grain Size

The bimodal-grain-size 7075 aluminium alloys containing varied ratios of large and small 7075 aluminium powders were prepared by spark plasma sintering (SPS). The large powder was 100 ± 15 μm in diameter and the small one was 10 ± 5 μm in diameter. The 7075 aluminium alloys was completely densified under the 500 °C sintering temperature and 60 MPa pressure. The large powders constituted coarse grain zone, and the small powders constituted fine grain zone in sintered 7075 aluminium alloys. The microstructural and microchemical difference between the large and small powders was remained in coarse and fine grain zones in bulk alloys after SPS sintering, which allowed for us to investigate the effects of microstructure and microchemistry on passive properties of oxide film formed on sintered alloys. The average diameter of intermetallic phases was 201.3 nm in coarse grain zone, while its vale was 79.8 nm in fine grain zone. The alloying element content in intermetallic phases in coarse grain zone was 33% to 48% higher than that on fine grain zone. The alloying element depletion zone surrounding intermetallic phases in coarse grain zone showed a bigger width and a more severe element depletion. The coarse grain zone in alloys showed a bigger electrochemical heterogeneity as compared to fine grain zone. The passive film formed on coarse grain zone had a thicker thickness and a point defect density of 2.4 × 1024 m−3, and the film on fine grain zone had a thinner thickness and a point defect density of 4.0 × 1023 m−3. The film resistance was 3.25 × 105 Ωcm2 on coarse grain zone, while it was 6.46 × 105 Ωcm2 on fine grain zone. The passive potential range of sintered alloys increased from 457 mV to 678 mV, while the corrosion current density decreased from 8.59 × 10−7 A/cm2 to 6.78 × 10−7 A/cm2 as fine grain zone increasing from 0% to 100%, which implied that the corrosion resistance of alloys increased with the increasing content of fine grains. The passive film on coarse grain zone exhibited bigger corrosion cavities after pitting initiation compared to that on fine grain zone. The passive film formed on fine grain zone showed a better corrosion resistance. The protectiveness of passive film was mainly determined by defect density rather than the thickness in this work.

Isotropic and Anisotropic Nanocrystalline NdFeB-Based Magnets Prepared by Spark Plasma Sintering and Hot Deformation

2012 ◽  
Vol 510-511 ◽  
pp. 307-314 ◽  
Author(s):  
Zhong Wu Liu ◽  
Y.L. Huang ◽  
H.Y. Huang ◽  
X.C. Zhong ◽  
Hong Ya Yu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Grain Growth ◽  
Spark Plasma Sintering ◽  
Hot Deformation ◽  
Grain Structure ◽  
Coarse Grain ◽  
Fine Grain ◽  
Plasma Sintering ◽  
Melt Spun ◽  
Spark Plasma

Isotropic and anisotropic NdFeB permanent magnets were prepared by Spark Plasma Sintering (SPS) and SPS followed hot deformation (HD), respectively, using melt spun NdFeB ribbons with various compositions as starting materials. It is found that, based on RE-rich composition, SPSed magnets sintered at low temperatures (<700 C) almost maintained the uniform fine grain structure inherited from rapid quenching. At higher temperatures, a distinct two-zone (coarse grain and fine grain zones) structure was formed in the SPSed magnets. The SPS temperature and pressure have important effects on the grain structure, which led to the variations in the magnetic properties. By employing low SPS temperature and high pressure, high-density magnets with negligible coarse grain zone and an excellent combination of magnetic properties can be obtained. For single phase NdFeB alloy, because of the deficiency of Nd-rich phases, it is relatively difficult to consolidate micro-sized melt spun powders into high density bulk magnet, but generally a larger particle size is beneficial to achieve better magnetic properties. Anisotropic magnets with a maximum energy product of ~38 MGOe were produced by the SPS+HD process. HD did not lead to obvious grain growth and the two-zone structure still existed in the hot deformed magnets. The results indicated that nanocrystalline NdFeB magnets without significant grain growth and with excellent properties could be obtained by SPS and HD processes.

scholarly journals Effect of Nano-Y2O3 Addition on Microstructure and Tensile Properties of High-Nb TiAl Alloy Prepared by Spark Plasma Sintering

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1048
Author(s):  
Yingchao Guo ◽  
Yongfeng Liang ◽  
Junpin Lin ◽  
Fei Yang
Keyword(s):  
Tensile Strength ◽  
Spark Plasma Sintering ◽  
Tial Alloy ◽  
Second Phase ◽  
Fine Grain ◽  
Fine Grain Strengthening ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Y2o3 Addition ◽  
Powder Metallurgy Route

Nano-Y2O3 reinforced Ti-47.7Al-7.1Nb-(V, Cr) alloy was fabricated by a powder metallurgy route using spark plasma sintering (SPS), and the influence of nano-Y2O3 contents on the microstructure and mechanical properties were investigated systematically. The results revealed that the ultimate tensile strength and elongation of the alloy were 570 ± 28 MPa and 1.7 ± 0.6% at 800 °C, 460 ± 23 MPa and 6.1 ± 0.4% at 900 °C with no nano-Y2O3, 662 ± 24 MPa and 5.5 ± 0.5% at 800 °C, and 466 ± 25 MPa and 16.5 ± 0.8% at 900 °C with 0.05 at% nano-Y2O3 addition, respectively. Due to the fine-grain strengthening and the second-phase strengthening, both tensile strength and elongation of the high-Nb TiAl alloy were enhanced with the addition of nano-Y2O3.

scholarly journals Powder Metallurgy Processing and Mechanical Properties of Controlled Ti-24Nb-4Zr-8Sn Heterogeneous Microstructures

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1626
Author(s):  
Benoît Fer ◽  
David Tingaud ◽  
Azziz Hocini ◽  
Yulin Hao ◽  
Eric Leroy ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Ball Milling ◽  
Processing Route ◽  
Fine Grain ◽  
Plasma Sintering ◽  
3D Network ◽  
Spark Plasma ◽  
Powder Particles ◽  
Heterogeneous Microstructures

This paper gives some insights into the fabrication process of a heterogeneous structured β-metastable type Ti-24Nb-4Zr-8Sn alloy, and the associated mechanical properties optimization of this biocompatible and low elastic modulus material. The powder metallurgy processing route includes both low energy mechanical ball milling (BM) of spherical and pre-alloyed powder particles and their densification by Spark Plasma Sintering (SPS). It results in a heterogeneous microstructure which is composed of a homogeneous 3D network of β coarse grain regions called “core” and α/β dual phase ultra-fine grain regions called “shell.” However, it is possible to significantly modify the microstructural features of the alloy—including α phase and shell volume fractions—by playing with the main fabrication parameters. A focus on the role of the ball milling time is first presented and discussed. Then, the mechanical behavior via shear tests performed on selected microstructures is described and discussed in relation to the microstructure and the probable underlying deformation mechanism(s).

Coarse-grain CeO2 doped ZrO2 ceramic prepared by spark plasma sintering

2020 ◽  
Vol 40 (14) ◽  
pp. 4844-4852
Author(s):  
Marek Vojtko ◽  
Viktor Puchy ◽  
Erika Múdra ◽  
Ondrej Milkovič ◽  
Alexandra Kovalčíková
Keyword(s):  
Spark Plasma Sintering ◽  
Coarse Grain ◽  
Plasma Sintering ◽  
Spark Plasma

Effect of Sintering Temperature on Microstructure and Mechanical Properties of Nanocrystalline Aluminum 5083 Alloy

2015 ◽  
Vol 782 ◽  
pp. 113-118
Author(s):  
Ying Mei Teng ◽  
Zhao Hui Zhang ◽  
Zi Zhou Yuan
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Compressive Strength ◽  
Sintering Temperature ◽  
Initial Pressure ◽  
Fine Grain ◽  
Microstructure And Mechanical Properties ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Bulk Nanocrystalline

The bulk nanocrystalline (NC) aluminum (Al) 5083 was synthesized by spark plasma sintering (SPS) technique with low initial pressure of 1 MPa, high holding pressure of 300 MPa and holding time of 4 min at different sintering temperatures, using surface passivated nanopowders. The effect of sintering temperature on microstructure and mechanical properties of the bulk NC Al 5083 were investigated. Results indicate that the density, grain size, the hardness and the compressive strength of the bulk NC Al 5083 increase with an increase in sintering temperature. The mechanical properties of the material are greatly improved due to the fine grain size. The bulk NC Al 5083 sintered at 723 K has the highest micro-hardness of 2.37 GPa and the best compressive strength of 845 MPa.

Effect of Grain Size on Phase Transitions and Dielectric Properties of Nano-Crystalline Barium Titanate Ceramics

2012 ◽  
Vol 602-604 ◽  
pp. 192-196
Author(s):  
Li Ming Wang ◽  
Xiang Yun Deng ◽  
Hai Tao Zhang ◽  
Jian Bao Li ◽  
Di Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Grain Size ◽  
Phase Transitions ◽  
Barium Titanate ◽  
Fine Grain ◽  
Nano Crystalline ◽  
Plasma Sintering ◽  
Transmission Electron ◽  
Spark Plasma ◽  
Titanate Ceramics

Barium titanate (BaTiO3) ceramics with grain size varied from 1000 to 8 nm were prepared by two step sintering method (TSS) and spark plasma sintering (SPS), respectively. Mixture structures of BaTiO3 ceramics were proved by in-situ temperature high resolution x-ray diffraction. Multiple ferroelectric domains present in nano-crystalline BaTiO3 ceramics were observed by transmission electron microscope. The evolution of phase transitions supported the existence of intrinsic mechanism. Dielectric loss of fine grain size BaTiO3 was higher than coarse grain size during Curie phase transition due to diffuse phase transition and grain boundary effects.

Al-Fe Chips Processed by High-Energy Ball Milling and Spark Plasma Sintering

2017 ◽  
Vol 270 ◽  
pp. 197-204 ◽  
Author(s):  
Vojtěch Kučera ◽  
Filip Průša ◽  
Dalibor Vojtěch
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Ball Milling ◽  
Spark Plasma Sintering ◽  
Iron Content ◽  
Aluminium Alloys ◽  
High Energy ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Energy Ball

Typically, conventional casting technologies are employed to manufacture aluminium alloys from scrap, but during recycling iron accumulates and increases in content. Increased iron content in such alloys reduces their mechanical properties. Because powder metallurgy is able to prepare materials with a very fine microstructure, we investigated its use for the preparation of aluminium alloys with a high iron content and the required mechanical properties. We prepared an Al-Fe17 (wt. %) binary alloy using combination of mechanical working (MW), high-energy ball milling (HEBM) and spark plasma sintering (SPS). The thus-prepared samples were analyzed (XRD, XRF, SEM-EDS, compression stress-strain test) and compared to the commercially-available alloy Al-Si12-Cu1-Mg1-Ni1, which is thermally stable. While the MW followed by SPS sample showed improved plastic deformation, the combination of MW, HEBM and SPS led to the absence of plastic deformation at room temperature. However, the MW+HEBM+SPS had much higher strength (579 MPa) and possessed similar thermal stability as the commercial Al-Si12-Cu1-Mg1-Ni1.

High Hardness BaCb-(BxOy/BN) Composites with 3D Mesh-Like Fine Grain-Boundary Structure by Reactive Spark Plasma Sintering

2012 ◽  
Vol 12 (2) ◽  
pp. 959-965 ◽  
Author(s):  
Oleg Vasylkiv ◽  
Hanna Borodianska ◽  
Petre Badica ◽  
Salvatore Grasso ◽  
Yoshio Sakka ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Spark Plasma Sintering ◽  
High Hardness ◽  
Boundary Structure ◽  
3D Mesh ◽  
Fine Grain ◽  
Grain Boundary Structure ◽  
Plasma Sintering ◽  
Spark Plasma
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