Low Temperature Sintering and Deformation of Nanocrystalline TiO2

1990 ◽  
Vol 196 ◽  
Author(s):  
H. Hahn ◽  
J. Logas ◽  
H. J. Höfler ◽  
P. Kurath ◽  
R. S. Averback
Keyword(s):  
Grain Size ◽  
Diffusion Coefficients ◽  
Pressureless Sintering ◽  
Strain Rates ◽  
Low Temperature Sintering ◽  
Compression Tests ◽  
Nanocrystalline Tio2 ◽  
Deformation Kinetics ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTThe sintering and deformation kinetics of nanocrystalline (n-) TiO2 were studied. It was found that pressureless sintering yields densities above 95 % with modest increase in grain size whereas pressure assisted sintering (1GPa) results in high density samples without grain growth. In addition compression tests were performed. Large true strains up to 0.6 and strain rates as high as 8 × 10−5 s−1 were observed at 810 °C without fracturing. The sintering and creep results are discussed in terms of the microstructure and diffusion coefficients in n-TiO2.

Elastic Modulus of Pb/Sn Solder Joints in Microelectronics

2002 ◽  
Author(s):  
Cemal Basaran ◽  
Jianbin Jiang
Keyword(s):  
Grain Size ◽  
Elastic Modulus ◽  
Single Crystal ◽  
Solder Alloy ◽  
Ultrasonic Testing ◽  
Heterogeneous Materials ◽  
Testing Methods ◽  
Nano Indentation ◽  
Deformation Kinetics ◽  
Kinetics Of

Young’s modulus (E) values published in literature for the eutectic Pb37/Sn63 and near eutectic Pb40/Sn60 solder alloy vary significantly. One reason for this discrepancy is different testing methods for highly rate sensitive heterogeneous materials, like Pb/Sn alloys, yield different results. In this paper, we study different procedures used to obtain the elastic modulus; analytically, by single crystal elasticity and experimentally by ultrasonic testing and Nano indentation. We compare these procedures and propose a procedure for elastic modulus determination. The deformation kinetics of the Pb/Sn solder alloys is discussed at the grain size level.

Refinement of Size Distributions for Primary Crystallizations

1997 ◽  
Vol 481 ◽  
Author(s):  
E. Pineda ◽  
T. Pradell ◽  
D. Crespo ◽  
N. Clavaguera ◽  
J. ZHU ◽  
...  
Keyword(s):  
Grain Size ◽  
Metastable Phase ◽  
Primary Crystallization ◽  
Controlled Growth ◽  
Diffusion Controlled ◽  
Average Grain Size ◽  
Soft Impingement ◽  
Single Grain ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTThe microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled.

scholarly journals Mechanical Properties of Dye 3 Greenland Deep Ice Cores

1984 ◽  
Vol 5 ◽  
pp. 1-8 ◽  
Author(s):  
Nobuhiko Azuma ◽  
Akira Higashi
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Power Law ◽  
Ice Core ◽  
Ice Cores ◽  
Uniaxial Stress ◽  
Strain Rates ◽  
Compression Tests ◽  
Polycrystalline Ice ◽  
Relationship Of

Uniaxial compression tests were carried out with specimens cut from several deep ice cores obtained at Dye 3, Greenland, in 1980 and 1981. The power law relationship of = Αση was obtained between the uniaxial strain-rate and the uniaxial stress σ. In a range of strain-rates between 10−8 and 10−7 s−1, the value of the power n for samples with strong single maximum fabric was approximately 4, significantly larger than the value of 3 which has been generally accepted from experiments using artificial polycrystalline ice. A work-hardening effect was found in the ice-core samples taken from a depth of 1900 m, which had a smaller grain size than the others. Recrystallization occurred when the temperature of the specimen was raised during the test and this ultimately caused the formation of the so-called diamond pattern ice fabric.

scholarly journals Study of Static Recrystallization Kinetics and the Evolution of Austenite Grain Size by Dynamic Recrystallization Refinement of an Eutectoid Steel

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1289
Author(s):  
Cesar Facusseh ◽  
Armando Salinas ◽  
Alfredo Flores ◽  
Gerardo Altamirano
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Static Recrystallization ◽  
Controlled Rolling ◽  
Strain Rates ◽  
Peak Strain ◽  
Compression Tests ◽  
Eutectoid Steel ◽  
Austenite Grain Size ◽  
Austenite Grain

Interrupted and continuous hot compression tests were performed for eutectoid steel over the temperature range of 850 to 1050 °C and while using strain rates of 0.001, 0.01, 0.1, and 1 s−1. The interrupted tests were carried out to characterize the kinetics of static recrystallization(SRX) and determinate the interpass time conditions that are required for initiation and propagation of dynamic recrystallization (DRX), while considering that the material does not contain microalloying elements additions for the recrystallization delay. Continuous testing was used to investigate the evolution of the austenite grain size that results from DRX. The results indicate that carbon content accelerates the SRX rate. This effect was observed when the retardation of recrystallization due to a decrease in deformation temperature from 1050 to 850 °C was only about one order of magnitude. The expected decelerate effect on the SRX rate when the initial grain size increases from 86 to 387 µm was not significant for this material. Although the strain parameter has a strong influence on SRX rate, in contrast to a lesser degree of strain rate, both of the effects are nearly independent of the chemical composition. The calculated maximum interpass times that are compatible with DRCR (Dynamic Recrystallization Controlled Rolling), for relatively low strain rates, suggest that the onset and maintaining of the DRX is possible. However, while using the empirical equations that were developed in the present work to estimate the maximum times for high strain rates, such as those observed in the wire and rod mills, indicate that the DRX start is feasible, but maintaining this mechanism for 5% softening in each pass after peak strain is not possible.

Effect of Silver on Superplastic Deformation in YBa2Cu3O7–x/Ag Composites

2002 ◽  
Vol 17 (5) ◽  
pp. 1172-1177
Author(s):  
Jondo Yun ◽  
Ye T. Chou ◽  
Martin P. Harmer
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Superplastic Deformation ◽  
Close Agreement ◽  
Silver Content ◽  
Strain Rates ◽  
Compression Tests ◽  
Fine Grained ◽  
Soft Inclusion ◽  
Activation Energy Of Deformation

Superplastic deformation was studied in fine-grained (0.7–1.1 μm) YBa2Cu3O7–x/Ag composites containing 2.5–25 vol% Ag. The compression tests were conducted in the temperature range of 750–875 °C and at strain rates of 10−5 to 10−3/s. For the YBa2Cu3O7−x/25%Ag composites with grain size of 0.7–1.1 μm, deformed at 800–850 °C and 10−5 to 10−3/s, the stress exponent, grain size exponent, and the activation energy of deformation were 2.0 ± 0.1, 2.5 ± 0.7, and 760 ± 100 kJ/mol, respectively. These values were the same as those of the pure YBa2Cu3O7−x, indicating that the deformation of the composite was controlled by that of the rigid YBa2Cu3O7−x phase. However, the strain rate was increased by the addition of silver as explained by the soft inclusion model of Chen. The dependence of the flow stress on the silver content was in close agreement with the prediction of the model.

Effect of Changing Strain Rate during Warm Deformation on Static Recrystallisation of IF Steel

2007 ◽  
Vol 550 ◽  
pp. 3-12
Author(s):  
C. Prentice ◽  
C.M. Sellars
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Subgrain Size ◽  
Constant Strain Rate ◽  
Salt Bath ◽  
Interstitial Free ◽  
Compression Tests ◽  
Constant Rate ◽  
Interstitial Free Steel ◽  
Kinetics Of

Plane strain compression tests have been carried out on Ti stabilised interstitial free steel at 700oC with constant and changing strain rates. Specimens were annealed in a salt bath at 750oC to determine the effects of changing strain rate on the kinetics of static recrystallisation and on the recrystallised grain size. After relatively slow changes in rate, the recrystallisation behaviour at the end of the change was the same as for tests at constant strain rate with the final value. For faster changes in rate, there were transients in recrystallisation rate and recrystallised grain size at the end of the change in strain rate at a strain of 1.0. These were removed by a further increment of 0.1 strain at constant rate. In all cases the recrystallised grain size correlated with the subgrain size present at the end of deformation.

Kinetics of Dynamic Recrystallization of 18 Ni Maraging Steels

2016 ◽  
Vol 850 ◽  
pp. 13-20 ◽  
Author(s):  
Ni Li ◽  
Fei Zhao ◽  
Huan Zhang ◽  
Yong Hai Ren
Keyword(s):  
Dynamic Recrystallization ◽  
Peak Stress ◽  
Strain Rates ◽  
Recrystallization Behavior ◽  
Compression Tests ◽  
Flow Curves ◽  
Maraging Steels ◽  
Dynamic Recrystallization Behavior ◽  
Characteristic Values ◽  
Kinetics Of

The dynamic recrystallization behavior of 18 Ni maraging steels was investigated by hot compression tests at temperatures ranging from 900 °C to 1100 °C and strain rates ranging from 0.001 to 1 s-1. Based on the flow curves from the tests, the effects of temperatures and strain rates on the dynamic recrystallization behavior were analyzed. The strain-hardening rates versus stress curves were used to determine to the critical strain, the peak stress (strain), the saturated stress and the steady stress. With the assistance of the process parameters, constitutive equations were obtained and the activation energy was determined to be 413544.96 J/mol. The dependence of the characteristic values on Zener-Hollomon was found. The dynamic recrystallization kinetics model of the tested steels was constructed and the validity was confirmed based on the experimental results.

scholarly journals Dynamic Precipitation in Mg–8.08Gd–2.41Sm–0.30Zr Alloy during Hot Compression

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2147
Author(s):  
Limin Zhu ◽  
Quanan Li ◽  
Qing Zhang ◽  
Xiaoya Chen
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Compression ◽  
Strain Rates ◽  
Dynamic Precipitation ◽  
Compression Tests ◽  
Effects Of Temperature ◽  
Compression Temperature

Dynamic precipitation of Mg–8.08Gd–2.41Sm–0.30Zr (wt %) alloy during hot compression was studied in the present work. The effects of temperature and strain rate on dynamic precipitation, and the effects of dynamic precipitation on dynamic recrystallization (DRX) and microhardness, were systematically analyzed. For this purpose, hot compression tests were conducted at the strain rates of 0.002~1 s−1 and temperatures of 350~500 °C, with the compaction strain of 70% (εmax = 0.7). The obtained results revealed that dynamic precipitation occurred during hot compression at 350~400 °C, but did not occur for T ≥ 450 °C. The precipitates were demonstrated to be β-Mg5Gd with a size of 200~400 nm, and they were distributed in the DRXed region. Dynamic precipitation occurred at strain rates in the 0.002~0.01 s−1 range, but did not occur when the strain rates were in the 0.1~1 s−1 range for the hot compression temperature of 350 °C. The relationships between the hot compression temperature (T) and DRXed grain size (lnd), microhardness (Hv), and DRXed grain size (d−1/2) of Mg–8.08Gd–2.41Sm–0.30Zr alloy were obtained.

Grain Size and the Compressive Strength of Ice

1985 ◽  
Vol 107 (3) ◽  
pp. 369-374 ◽  
Author(s):  
D. M. Cole
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
Strain Rate ◽  
Peak Stress ◽  
Applied Strain ◽  
Test Material ◽  
Strain Rates ◽  
Grain Size Effect ◽  
Compression Tests ◽  
Polycrystalline Ice

This work presents the results of uniaxial compression tests on freshwater polycrystalline ice. Grain size of the test material ranged from 1.5 to 5 mm, strain rate ranged from 10−6 to 10−2 s−1 and the temperature was −5°C. The grain size effect emerged clearly as the strain rate increased to 10−5 s−1 and persisted to the highest applied strain rates. On average, the stated increase in grain size brought about a decrease in peak stress of approximately 31 percent. The occurrence of the grain size effect coincided with the onset of visible cracking. The strength of the material increased to a maximum at a strain rate of 10−3 s−1, and then dropped somewhat as the strain rate increased further to 10−2 s−1. Strain at peak stress generally tended to decrease with both increasing grain size and increasing strain rate. The results are discussed in terms of the deformational mechanisms which lead to the observed behavior.

Sign in / Sign up

Export Citation Format

Share Document