Grain Boundary Characterization in Yttria-Stabilized Zirconia by TEM Spectrum Lines

2000 ◽  
Vol 6 (S2) ◽  
pp. 220-221
Author(s):  
N. D. Evans ◽  
P. H. Imamura ◽  
M. L. Mecartneyf
Keyword(s):  
Grain Boundary ◽  
Tetragonal Zirconia ◽  
Light Element ◽  
Grain Boundary Sliding ◽  
Crystalline Materials ◽  
Fine Grained ◽  
User Facility ◽  
Near Net Shape ◽  
Net Shape Forming ◽  
Boundary Sliding

The superplasticity exhibited by some fine-grained ceramics, notably 3-mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP), offers interesting possibilities to lower manufacturing costs by near net shape forming. Both glassy and crystalline materials have been added to pure 3 Y-TZP to limit grain growth and promote grain boundary sliding during sintering and isostatic pressing. EDS spectrum lines have been used to characterize the distribution and extent of additive phases, but were not able to map some light-element components of additives (e.g., O and B in borosilicate glass). Additionally, quantification of the Si Kα peak was compromised by overlap with the Y L and Z L peaks. To both improve light element sensitivity and investigate potential changes in oxygen bonding at the grain boundaries, undoped 3 Y-TZP and 3 Y-TZP powders processed with 1 wt% barium silicate have been examined with TEM spectrum lines. Additionally, some elemental mapping has been performed. TEM specimens were examined in a 300 kV LaB6 Philips CM30T equipped with a Gatan imaging filter (GIF) at the ORNL SHaRE User Facility.

scholarly journals Characterization of Intergranular Phases in Tetragonal and Cubic Yttria-Stabilized Zirconia

1998 ◽  
Vol 4 (S2) ◽  
pp. 584-585
Author(s):  
N.D. Evans ◽  
P.H. Imamura ◽  
J. Bentley ◽  
M.L. Mecartney
Keyword(s):  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Tetragonal Zirconia ◽  
Potential Method ◽  
Grain Boundary Sliding ◽  
Fine Grained ◽  
Net Shape Forming ◽  
Boundary Sliding ◽  
Ceramic Manufacturing

Achieving superplasticity in fine-grained ceramics is a potential method to lower energy costs associated with ceramic manufacturing via net shape forming. Superplasticity is intrinsic in 3-mol%- yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP), and can be enhanced by addition of glass to form intergranular phases which are thought to both limit grain growth and promote grain boundary sliding during processing (sintering and hot isostatic pressing). This permits processing at lower temperatures. However, superplasticity has not been observed in 8-mol%-yttria-stabilized cubic zirconia (8Y-CSZ), ostensibly due to its larger grain size and high grain growth rates.3,4 As part of a larger study, high-spatial-resolution energy-dispersive X-ray spectrometry (EDS) has been performed on 3Y-TZP and 8Y-CSZ specimens doped with various glassy phases to characterize intergranular compositions.Zirconia powders were mixed with glass to produce specimens having either 1 wt % lithiumaluminum- silicate, 1 wt % barium-silicate, or 1 wt % borosilicate. Some specimens were prepared without added glass.

Role of Vacancies and Solute Atoms on Grain Boundary Sliding

1999 ◽  
Vol 601 ◽  
Author(s):  
J.S. Vetrano ◽  
C.H. Henager ◽  
E.P. Simonen
Keyword(s):  
Grain Boundary ◽  
Solute Atom ◽  
Vacancy Concentration ◽  
Grain Boundary Sliding ◽  
Fine Grained ◽  
Grain Boundary Plane ◽  
Transmission Electron ◽  
Boundary Sliding ◽  
Solute Atoms

AbstractIt is necessary for grain boundary dislocations to slide and climb during the grain boundary sliding process that dominates fine-grained superplastic deformation. The process of climb requires either an influx of vacancies to the grain boundary plane or a local generation of vacancies. Transmission electron microscopy (TEM) observations of grain boundaries in superplastically deformed Al-Mg-Mn alloys quenched under load from the deformation temperature have revealed the presence of nano-scale cavities resulting from a localized supersaturation of vacancies at the grain boundary. Compositional measurements along interfaces have also shown an effect of solute atoms on the local structure. This is shown to result from a coupling of vacancy and solute atom flows during deformation and quenching. Calculations of the localized vacancy concentration indicate that the supersaturation along the grain boundary can be as much as a factor often. The effects of the local supersaturation and solute atom movement on deformation rates and cavity nucleation and growth will be discussed.

Deformation of fine-grained alumina by grain boundary sliding accommodated by slip

2003 ◽  
Vol 51 (12) ◽  
pp. 3617-3634 ◽  
Author(s):  
Oscar A. Ruano ◽  
Jeffrey Wadsworth ◽  
Oleg D. Sherby
Keyword(s):  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Fine Grained ◽  
Boundary Sliding

Effect of Hydrostatic Pressure on Nano Crystalline Materials Behavior

2012 ◽  
Vol 18-19 ◽  
pp. 27-42 ◽  
Author(s):  
Reza Jafari Nedoushan ◽  
Mahmoud Farzin
Keyword(s):  
Grain Size ◽  
Hydrostatic Pressure ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Crystalline Materials ◽  
Nano Crystalline ◽  
Tension And Compression ◽  
Boundary Sliding ◽  
Tension Compression Asymmetry ◽  
Effect Of Hydrostatic Pressure

One of the Remarkable Differences between Mechanical Behavior of Nano-Crystalline and Coarse-Grained Materials Is Tension Compression Asymmetry that Has Been Experienced in Nano-Crystalline Materials. In this Paper a Constitutive Model Is Proposed which Considers Dominant Operative Deformation Mechanisms of Nano-Crystalline Materials Including Grain Interior Plasticity, Grain Boundary Diffusion and Grain Boundary Sliding. A Grain Size Dependent Taylor Type Polycrystalline Model Is Used to Predict Grain Interior Deformation. Three Dimensional Relationships Are Proposed to Relate Macro Stress and Strain Rate in Grain Boundary Mechanisms. The Effect of Normal Stress Acting on a Boundary Is Also Considered in Grain Boundary Sliding, Therefore, Effect of Hydrostatic Pressure Is Included in the Model. The Proposed Model Is Used to Predict Strength of Nano-Crystalline Copper in both Tension and Compression and Good Results Are Obtained Comparing with Experimental Data. The Model Also Predicts Various Behaviors of Nano-Crystalline Materials Observed in Literature's Experiments and Molecular Dynamic Simulations. Some Examples Are: Inverse Hall-Petch Effect; Tension and Compression Maximum Strength Grain Sizes; Tension Compression Asymmetry and its Change Vs. Grain Size and Strain Rate and the Yield Locus Shape.

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