Superplastic Extrusion of Al2O3-YTZ Nanocomposite and Its Deformation Mechanism

2005 ◽  
Vol 475-479 ◽  
pp. 2973-2976 ◽  
Author(s):  
Guo Qing Chen ◽  
Kai Feng Zhang
Keyword(s):  
Elevated Temperature ◽  
Grain Growth ◽  
Deformation Mechanism ◽  
Tetragonal Zirconia ◽  
Extrusion Pressure ◽  
Second Phase ◽  
Temperature Range ◽  
Punch Speed ◽  
Dynamic Grain Growth

Using Al2O3-YTZ(3mol% yttria stabilized tetragonal zirconia) nanocomposite, superplastic extrusion under different conditions was adopted to form blade models. The results demonstrate that desired microstructure is achieved through the addition of 20mol% YTZ which acts as a second-phase pinning agent. At temperature range of 1650°C to 1700°C the material shows good deformability. At this elevated temperature the maximum extrusion pressure is lower than 25MPa, and the maximum punch speed is about 0.35mm·min-1. In superplastic extrusion the dominating deformation mechanism is grain sliding and rotation, the accommodating mechanism is intergranular zirconia coordinated deformation. Meanwhile static and dynamic grain growth also plays an important role in deformation.

Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

1988 ◽  
Vol 46 ◽  
pp. 550-551
Author(s):  
R. E. Franck ◽  
J. A. Hawk ◽  
G. J. Shiflet
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Grain Growth ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Second Phase ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

Dynamic Grain Growth in Superplastic Y-TZP and Al2O3/YTZ

1990 ◽  
Vol 196 ◽  
Author(s):  
T. G. Nieh ◽  
C. M. Tomasello ◽  
J. Wadsworth
Keyword(s):  
Growth Rate ◽  
Grain Size ◽  
Grain Growth ◽  
Kinetic Constant ◽  
Boundary Energy ◽  
Tetragonal Zirconia ◽  
Grain Boundary Energy ◽  
Fine Grained ◽  
Dynamic Grain Growth ◽  
Similar Equation

ABSTRACTBoth static and dynamic grain growth have been studied during superplastic deformation of fine-grained yttria-stabilized tetragonal zirconia (Y-TZP) and alumina reinforced yttria-stabilized tetragonal zirconia (Al2O3/YTZ). Grain growth was observed in both materials at temperatures above 1350° C. In the case of Y-TZP, both static and dynamic grain growth were found to obey a similar equation of the form: where D is the instantaneous grain size, Do is the initial grain size, t is the time, and k is a kinetic constant which depends primarily on temperature and grain boundary energy. The activation energies for Y-TZP were approximately 580 and 520 kJ/mol, for static and dynamic grain growth, respectively. In the case of Al2O3/YTZ, it was found that the grain growth rate for the Al2O3 phase was slower than that for the ZrO2 phase. The growth rate of the ZrO2 phase in Al2O3/YTZ is, however, similar to that in monolithic ZrO2, i.e., Y-TZP.

Grain Refinement in Titanium-Erbium Alloys

1974 ◽  
Vol 32 ◽  
pp. 522-523
Author(s):  
B. B. Rath ◽  
J. E. O'Neal ◽  
R. J. Lederich
Keyword(s):  
Electron Microscopy ◽  
Size Distribution ◽  
Grain Refinement ◽  
Grain Growth ◽  
Volume Fraction ◽  
Pure Titanium ◽  
Systematic Investigation ◽  
Second Phase ◽  
Titanium Matrix ◽  
Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

scholarly journals Hot Deformation Behavior and Processing Maps of a New Ti-6Al-2Nb-2Zr-0.4B Titanium Alloy

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2456
Author(s):  
Zhijun Yang ◽  
Weixin Yu ◽  
Shaoting Lang ◽  
Junyi Wei ◽  
Guanglong Wang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Flow Stress ◽  
Constitutive Equation ◽  
Deformation Mechanism ◽  
Power Dissipation ◽  
Hot Deformation ◽  
Dissipation Rate ◽  
Dynamic Recovery ◽  
Processing Maps ◽  
Temperature Range

The hot deformation behaviors of a new Ti-6Al-2Nb-2Zr-0.4B titanium alloy in the strain rate range 0.01–10.0 s−1 and temperature range 850–1060 °C were evaluated using hot compressing testing on a Gleeble-3800 simulator at 60% of deformation degree. The flow stress characteristics of the alloy were analyzed according to the true stress–strain curve. The constitutive equation was established to describe the change of deformation temperature and flow stress with strain rate. The thermal deformation activation energy Q was equal to 551.7 kJ/mol. The constitutive equation was ε ˙=e54.41[sinh (0.01σ)]2.35exp(−551.7/RT). On the basis of the dynamic material model and the instability criterion, the processing maps were established at the strain of 0.5. The experimental results revealed that in the (α + β) region deformation, the power dissipation rate reached 53% in the range of 0.01–0.05 s−1 and temperature range of 920–980 °C, and the deformation mechanism was dynamic recovery. In the β region deformation, the power dissipation rate reached 48% in the range of 0.01–0.1 s−1 and temperature range of 1010–1040 °C, and the deformation mechanism involved dynamic recovery and dynamic recrystallization.

Enlarging the Temperature Range for Maximum Wear Resistance of TiNi Alloy Using a NTE Phase

2007 ◽  
Vol 539-543 ◽  
pp. 3261-3266 ◽  
Author(s):  
Iulian Radu ◽  
Dong Yang Li
Keyword(s):  
Wear Resistance ◽  
Thermal Expansion ◽  
Internal Stress ◽  
Frictional Heating ◽  
Negative Thermal Expansion ◽  
High Wear Resistance ◽  
Tini Alloy ◽  
Wear Loss ◽  
Second Phase ◽  
Temperature Range

The near-equiatomic TiNi alloy has been demonstrated to possess high wear resistance, which largely benefits from its pseudoelasticity (PE). However, the PE occurs only in a small temperature range, which makes the wear resistance of this alloy unstable as temperature changes, caused by environmental instability or frictional heating. Therefore, enlarging the working temperature of PE could considerably improve this alloy as a novel wear-resistant material. One possible approach is to develop a self-built temperature-dependent internal stress field by taking the advance of the difference in thermal expansion between the pseudoelastic matrix and a reinforcing phase. Such a T-dependent internal stress could adjust the martensitic transformation temperature to respond changes in environmental temperature so that the temperature range of PE could be enlarged, thus leading to a wide temperature range in which the minimum wear loss is retained. Research was conducted to investigate effects of an added second phase having a negative thermal expansion (NTE) coefficient on the wear resistance of a near-equiatomic TiNi alloy. It was demonstrated that the temperature range of this modified material in which the wear loss dropped was enlarged. In addition, the wear resistance of such a TiNi-matrix composite was on one order of magnitude higher than that of unmodified TiNi alloy.

Dynamic grain growth in Al–6Ni: Modelling and experiments

2005 ◽  
Vol 53 (16) ◽  
pp. 4313-4321 ◽  
Author(s):  
K HYDE ◽  
P BATE
Keyword(s):  
Grain Growth ◽  
Dynamic Grain Growth
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