High-temperature stability of nanocrystalline structure in a TiAl alloy prepared by mechanical alloying and hot isostatic pressing

1998 ◽  
Vol 13 (12) ◽  
pp. 3399-3410 ◽  
Author(s):  
O. N. Senkov ◽  
N. Srisukhumbowornchai ◽  
M. L. Öveçoglu ◽  
F. H. Froes
Keyword(s):  
Grain Size ◽  
Mechanical Alloying ◽  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Nanocrystalline Structure ◽  
Temperature Stability ◽  
Growth Exponent ◽  
Pinning Force ◽  
High Temperature Stability ◽  
Isostatic Pressing

A fully dense nanocrystalline compact of the Ti–47Al–3Cr (at. %) alloy was produced by mechanical alloying and hot isostatic pressing at 725 °C. Microstructure characteristics and grain growth behavior of this compact were studied after annealing for up to 800 h in the temperature range of 725 to 1200 °C, using analytical transmission electron microscopy techniques. The temperature and time dependencies of the grain sizes and the grain size distributions were determined. The grain growth occurred, with a timeand temperature-invariant single-peak grain size distribution (when normalized by the mean grain size), which was consistent with normal grain growth. The experimentally measured grain growth exponent decreased from 10 to 4.6 when the temperature was increased. The grain growth kinetics was described by a single thermally activated rate process limited by a permanent pinning force on the grain boundaries. The microhardness decreased on annealing and followed the Hall–Petch relationship with the parameters Hυo = 5.8 GPa and KH = 1.6 MPa m0.5.

scholarly journals Structure-Property Correlation in Ir Transparent Zinc Sulphide (Zns) Ceramics Under Chemical Vapour Deposited & Hot Iso-Statically Pressed Conditions

2019 ◽  
Vol 3 (2) ◽  
Keyword(s):  
Grain Size ◽  
Hot Isostatic Pressing ◽  
Chemical Vapour ◽  
Complex Impedance ◽  
Ac Impedance ◽  
Spectroscopic Studies ◽  
Structure Property ◽  
Frequency Range ◽  
Equivalent Circuit Analysis ◽  
Isostatic Pressing

IR Transparent ZnS ceramics processed through chemical vapour deposition were subjected to Hot Isostatic pressing and the samples in both the conditions were characterized by XRD, microstructure and high temperature impedance spectroscopic studies for the dielectric and electrical properties. Both the samples have shown cubic sphalerite phase with enhanced orientation along (111) plane as a result of hot isostatic pressing as revealed by XRD.HIP treatment to ZnS facilitated the enhancement of the homogeneity of microstructure and enhancement in the grain size from 10μm to 50μm. The electrical behavior of both the samples was investigated by AC impedance spectroscopy in the frequency range 1Hz to 1MHz from RT to 500°C in dry air. HIP has resulted in a significant increase in the dielectric constant, which can be attributed to the increase in homogeneity and the grain size. Further, the complex impedance plots exhibited two impedance semicircles identified in the frequency range is explained by the grain and grain boundary effects. An equivalent-circuit analysis of AC impedance spectra based on the brick-layer model was performed. Activation energies obtained from the conductivity plots indicates an Arrhenius type thermally activated process.

Effect of Sintering Temperature on Structure and Dielectric Properties of Lead Free K0.5Na0.5NbO3 Prepared via Hot Isostatic Pressing

2017 ◽  
Vol 888 ◽  
pp. 42-46 ◽  
Author(s):  
Fatin Khairah Bahanurdin ◽  
Julie Juliewatty Mohamed ◽  
Zainal Arifin Ahmad
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Hot Isostatic Pressing ◽  
Solid State Reaction Method ◽  
Lead Free ◽  
Tangent Loss ◽  
Isostatic Pressing ◽  
Tan Δ

In this research, alkaline niobate known as K0.5Na0.5NbO3 (KNN) lead-free piezoelectric ceramic was synthesis by solid state reaction method which pressing at different sintering temperatures (1000 °C and 1080 °C) prepared via hot isostatic pressing (HIP)). The effect of sintering temperature on structure and dielectric properties was studied. The optimum sintering temperature (at 1080 °C for 30 minutes) using hot isostatic pressing (HIP) was successfully increase the density, enlarge the particle grain size in the range of 0.3 µm – 2.5 µm and improves the dielectric properties of K0.5Na0.5NbO3 ceramics. The larger grain size and higher density ceramics body will contribute the good dielectric properties. At room temperature, the excellent relative permittivity and tangent loss recorded at 1 MHz (ɛr = 5517.35 and tan δ = 0.954), respectively for KNN1080HIP sample. The KNN1080HIP sample is also exhibits highest relative density which is 4.485 g/cm3. The ɛr depends upon density and in this work, the density increase as the sintering temperature increase, which resulting the corresponding ɛr value also increases.

scholarly journals Chromium Effect as Grain Growth Inhibitor of Nanostructured WC-10Co after Sintering by Hot Isostatic Pressing

2018 ◽  
Vol 24 (S1) ◽  
pp. 2300-2301
Author(s):  
C. G. Garay-Reyes ◽  
M. A. Ruiz-Esparza-Rodriguez ◽  
I. Estrada Guel ◽  
S. E. Hernandez-Martinez ◽  
J.L. Hernandez-Rivera ◽  
...  
Keyword(s):  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Growth Inhibitor ◽  
Isostatic Pressing ◽  
Grain Growth Inhibitor ◽  
Chromium Effect

Temperature Dependent Mechanical Behavior of ODS Steels

2018 ◽  
Vol 941 ◽  
pp. 257-262
Author(s):  
Massimo de Sanctis ◽  
Alessandra Fava ◽  
Gianfranco Lovicu ◽  
Roberto Montanari ◽  
Maria Richetta ◽  
...  
Keyword(s):  
Grain Size ◽  
Mechanical Alloying ◽  
Mechanical Behavior ◽  
Hot Isostatic Pressing ◽  
Hot Extrusion ◽  
Oxide Dispersion Strengthened ◽  
Steel Powder ◽  
High Energy ◽  
Superior Mechanical Properties ◽  
Ods Steels

An oxide dispersion strengthened (ODS) ferritic steel with nanometric grain size has been produced by means of low-energy mechanical alloying (LEMA) of steel powder (Fe-14Cr-1W-0.4Ti) mixed with Y2O3 particles (0.3 wt%) and successive hot extrusion (HE). The material has equiaxed grains (mean size of 400 nm) and dislocation density of 4 x 1012 m-2, and exhibits superior mechanical properties with respect the unreinforced steel. The mechanical behavior has been compared with that of ODS steels prepared by means of the most common process, high-energy mechanical alloying (HEMA), consolidation through hot isostatic pressing (HIP) or hot extrusion (HE), annealing around 1100 °C for 1-2 hours, which produces a bimodal grain size distribution. The strengthening mechanisms have been examined and discussed to explain the different behavior.

Effect of Isothermal Sintering Time on the Properties of the Ceramic Composite ZrO2-Al2O3

2006 ◽  
Vol 530-531 ◽  
pp. 526-531 ◽  
Author(s):  
Claudinei dos Santos ◽  
L.H.P. Teixeira ◽  
J.K.M.F. Daguano ◽  
Kurt Strecker ◽  
Carlos Nelson Elias
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Ceramic Composite ◽  
Growth Exponent ◽  
Microstructural Development ◽  
Growth Equation ◽  
Sintering Time ◽  
Al2o3 Composite ◽  
Average Grain Size ◽  
Grain Size Distributions

In this work the influence of isothermal sintering time on the microstructural development of ZrO2-Al2O3 composite was studied. Powder mixture of ZrO2 containing 20 wt% Al2O3 was prepared by milling, compaction and sintering at 16000C, in air. The isothermal sintering time at 16000C was varied between 0 and 1440 min. The sintered samples were characterized in terms of phase composition and relative density. Their microstructures were characterized by grain size distributions and average grain size. These results were evaluated using the classic grain growth equation as a function of time, determining the grain growth exponent of these materials. Furthermore, the microstructural aspects were related to the mechanical properties (Vicker’s hardness and fracture toughness) of these composites.

Mechanical properties and low-temperature aging of tetragonal zirconia polycrystals processed by hot isostatic pressing

2003 ◽  
Vol 18 (10) ◽  
pp. 2415-2426 ◽  
Author(s):  
J. Muñoz-Saldaña ◽  
H. Balmori-Ramírez ◽  
D. Jaramillo-Vigueras ◽  
T. Iga ◽  
G. A. Schneider
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Low Temperature ◽  
Hot Isostatic Pressing ◽  
Tetragonal Zirconia ◽  
Hot Water ◽  
Full Density ◽  
Isostatic Pressing ◽  
Low Temperature Aging ◽  
Temperature Aging

The influence of grain size and density of yttria-tetragonal zirconia polycrystals (Y-TZPs) ceramics on mechanical properties and on low-temperature aging degradation (LTD) in air and in hot water was investigated. A TZP powder containing 3 mol% Y2O3 was consolidated by slip casting and densified by the sintering/hot isostatic pressing (HIP) method. Only the presintered samples that contained less than 0.15% open porosity reached near full density after HIP. The best conditions to reach full density were found to be attained by presintering and HIP both at 1400 °C. At these conditions, some of the best mechanical properties such as modulus of rupture and Weibull modulus reached 1397 ± 153 MPa and, 10.6, respectively. These values were clearly higher than those obtained from sintered bodies and samples hot isostatically pressed at 1600 °C. Aging degradation of 3Y-TZP materials can be avoided through microstructural design. Fully dense materials with a critical grain size <0.36 μm did not show any evidence of degradation after extreme aging conditions at pressurized autoclaving in hot water at 100, 200, and 260 °C for 8 h. We propose a criterion to predict degradation in air as well as in hot water for the characterized materials based on the microstructure and density control of the samples.

Simultaneous Synthesis and Sintering of Al2O3/Mo2N Composites Using Capsule-Free Nitrogen Hot Isostatic Pressing and their Characterization

2010 ◽  
Vol 62 ◽  
pp. 197-202
Author(s):  
Hirota Ken ◽  
Takaoka Katsuya ◽  
Murase Yasushi ◽  
Kato Masaki
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Vickers Hardness ◽  
Bending Strength ◽  
Hot Isostatic Pressing ◽  
Isostatic Pressing ◽  
Simultaneous Synthesis ◽  
Powder Compacts ◽  
Al2o3 Matrix

Synthesis of dense materials with the compositions of Al2O3/Mo2N=100/0 ~ 40/60 vol% has been attempted directly from Al2O3/Mo mixed raw powder compacts using capsule-free N2 hot isostatic pressing (HIP). During HIPing [1500°C/(16~20)MPa]/1h], solid/gas reaction between Mo and N2 was introduced to form Mo2N. Most sintered composites consisting of only Al2O3 and Mo2N phases reached a higher relative density than 98.0% with closed pores nevertheless capsule-free HIPing. Distribution of Mo2N particles just formed suppressed the grain growth of Al2O3 during sintering. Mechanical properties, such as bending strength (Σb), Vickers hardness (HV), fracture toughness (K1C), and other properties have been evaluated as a function of their compositions. The best mechanical values of Σb (c.a. 573 MPa), HV (c.a. 20.3 GPa) and K1C (c.a. 5.00 MPa･m1/2) were attained at the composition of Al2O3/Mo2N=90/10 vol%, due to a high density (98.6%) and small grain size of Al2O3 matrix (Gs c.a. 4.70 μm). Further addition of Mo2N reduced the sinterability of matrix grains, resulting in low densities of around 90% at the 40/60 vol% composition.

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