Search results for: P.F. Becher

Items from 1 to 16 out of 16 results

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Grain rotation and translation contribute substantially to creep of a zirconium diboride silicon carbide composite

M.W. Bird, P.F. Becher, K.W. White

Acta Materialia > 2015 > 89 > C > 73-87

Electron back scatter diffraction (EBSD) techniques as well as a novel microstructure mapping technique for the direct measurement of local grain-to-grain movements, provided the tools necessary for the assessment of creep deformation mechanisms of a ZrB₂–20% SiC composite. Flexure creep behavior determined here draws upon our previous research conducted at 1800°C and 16 through 97MPa for the same...

article

Local dislocation creep accommodation of a zirconium diboride silicon carbide composite

M.W. Bird, T. Rampton, D. Fullwood, P.F. Becher, more

Acta Materialia > 2015 > 84 > C > 359-367

A grain boundary sliding creep mechanism, accommodated by “mantle” dislocation activities, is shown to allow for large strain (ε>0.08) during the creep of a ZrB₂–20% SiC composite at 1800°C. We characterized the local grain deformation behavior using high-resolution electron backscatter diffraction microscopy and an indentation deformation mapping technique. Deformation gradients near grain boundaries...

article

Mechanisms of toughening in silicon nitrides: The roles of crack bridging and microstructure

S. Fünfschilling, T. Fett, M.J. Hoffmann, R. Oberacker, more

Acta Materialia > 2011 > 59 > 10 > 3978-3989

Crack-bridging mechanisms can provide substantial increases in toughness coupled with strength in ceramics. Herein, we describe the various bridging mechanisms, their toughening contributions and how they are affected by microstructure in silicon nitride ceramics, which are a classic example where both high strength and toughness are achieved. Crack growth resistance curves (R-curves) for seven different...

article

Controlled normal/shear loading and shear fracture in bulk metallic glasses

C.H. Hsueh, H. Bei, C.T. Liu, E.P. George, more

Intermetallics > 2009 > 17 > 10 > 802-810

Limited plasticity inhibits the engineering applications of bulk metallic glasses (BMGs), which often deform by the formation of localized shear bands. Overcoming the brittleness of BMGs necessitates advances in our understanding of the mechanisms of shear band initiation and propagation. Up to now, a major hurdle has been the ability to control the generation of shear bands and the associated fracture...

article

Shear fracture of bulk metallic glasses with controlled applied normal stresses

C.H. Hsueh, H. Bei, C.T. Liu, P.F. Becher, more

Scripta Materialia > 2008 > 59 > 1 > 111-114

The Mohr–Coulomb criterion has been invoked to characterize the dependence of shear fracture of bulk metallic glasses on the stress normal to the shear plane. However, systematic verification of its applicability is lacking. We use a unique test fixture that is capable of controlling (i) the location of shear fracture and (ii) the ratio of the normal to shear stress on the fracture plane to perform...

article

Composition and local bonding in RE–Si–M–O–N (M=Mg, Al ; RE=La, Lu) glasses

V. Fouquet-Parry, F. Paumier, M.J. Guittet, M. Gautier-Soyer, more

Applied Surface Science > 2008 > 254 > 15 > 4665-4670

Two series of oxynitride glasses, RE–Si–Mg–O–N (M=Mg, Al ; RE=La, Lu), have been studied by X-Ray photoelectron spectroscopy (XPS). The oxygen 1s photoelectron lineshape reveals a striking difference depending on the rare earth, both in the Mg series and in the Al series. Specifically, the oxygen 1s photoelectron lines of the La doped glasses are broader than the ones of the Lu doped glasses. This...

article

Analyses of layer-thickness effects in bilayered dental ceramics subjected to thermal stresses and ring-on-ring tests

C.H. Hsueh, G.A. Thompson, O.M. Jadaan, A.A. Wereszczak, more

Dental Materials > 2008 > 24 > 1 > 9-17

The purpose of this study was to analyze the stress distribution through the thickness of bilayered dental ceramics subjected to both thermal stresses and ring-on-ring tests and to systematically examine how the individual layer thickness influences this stress distribution and the failure origin.Ring-on-ring tests were performed on In-Ceram Alumina/Vitadur Alpha porcelain bilayered disks with porcelain...

article

Modelling of bonded multilayered disks subjected to biaxial flexure tests

C.H. Hsueh, C.R. Luttrell, P.F. Becher

International Journal of Solids and Structures > 2006 > 43 > 20 > 6014-6025

Biaxial flexure tests have been used extensively for the strength measurements of monolithic brittle materials. However, despite the increasing applications of multilayered structures, characterization of their strengths using biaxial flexure tests is unavailable. This is because the analytical description of the relation between the strength and the fracture load for multilayers subjected to biaxial...

article

Influence of additives on anisotropic grain growth in silicon nitride ceramics

P.F. Becher, G.S. Painter, N. Shibata, R.L. Satet, more

Materials Science & Engineering A > 2006 > 422 > 1-2 > 85-91

Tailoring microstructure and composition are critical components for obtaining high-performance silicon nitride (Si ₃ N ₄ ) ceramics. Anisotropic growth behavior of Si ₃ N ₄ grains can be used to form very elongated grains, which serve to reinforce the matrix analogous to whisker-reinforcement of ceramics. The Si ₃ N ₄ grain morphology is known to be...

article

Deflection versus penetration of a wedge-loaded crack: effects of branch-crack length and penetrated-layer width

M.Y. He, C.H. Hsueh, P.F. Becher

Composites Part B > 2000 > 31 > 4 > 299-308

A crack intersecting an interface between two dissimilar material layers may advance by either deflecting along or penetrating through the interface. The criterion of deflection versus penetration can be established by the comparison of two ratios, the energy release rate ratio and the fracture energy ratio, of deflection to penetration. The effects of: (1) a finite length of the branch crack emanating...

article

Properties of silicon-aluminum-yttrium oxynitride glasses

E.Y. Sun, P.F. Becher, S.-L. Hwang, S.B. Waters, more

Journal of Non-Crystalline Solids > 1996 > 208 > 1-2 > 162-169

The thermal and mechanical properties of two Si-Al-Y-O-N systems, including linear thermal expansion coefficient, glass transition temperature, elastic modulus, hardness and fracture toughness, were characterized. Results are compared with those previously reported in the literature in an attempt to expand our knowledge of silicon oxynitride glasses. It is found that increasing the nitrogen content...

article

Debonding of interfaces between beta-silicon nitride whiskers and Si Al Y oxynitride glasses

P.F. Becher, E.Y. Sun, Chun-Hway Hsueh, K.B. Alexander, more

Acta Materialia > 1996 > 44 > 10 > 3881-3893

Crack bridging mechanisms in self-reinforced silicon nitride ceramics rely on interfacial debonding and intergranular fracture processes. The toughening effects can be enhanced by increasing the diameter of the elongated grains. However, the composition of the additives and, hence, the grain boundary amorphous phase can significantly alter this response; the question remains as to whether this is...

article

Ceramic composites with a ductile Ni3Al binder phase

T.N. Tiegs, K.B. Alexander, K.P. Plucknett, P.A. Menchhofer, more

Materials Science & Engineering A > 1996 > 209 > 1-2 > 243-247

Composites of B-doped ductile Ni ₃ Al alloys with both non-oxide (WC, TiC) and oxide (Al ₂ O ₃ ) ceramic powders were produced by hot-pressing. The Ni ₃ Al alloys wet the non-oxide ceramic powders well and form a semi-continuous intergranular phase. However, the Ni ₃ Al alloys do not wet the oxide powders well and tend to form discrete “islands” of the metallic...

article

Ni ₃ AlAl ₂ O ₃ composites with interpenetrating networks

J. Rödel, H. Prielipp, N. Claussen, M. Sternitzke, more

Scripta Metallurgica et Materiala > 1995 > 33 > 5 > 843-848

article

Transformation behavior in Al2O3ZrO2 ceramic composites

X.-L. Wang, J.A. Fernandez-Baca, C.R. Hubbard, K.B. Alexander, more

Physica B: Physics of Condensed Matter > 1995 > 213-214 > Complete > 824-826

Neutron powder diffraction was used to investigate the tetragonal-to-monoclinic transformation of ZrO ₂ in an Al ₂ O ₃ ZrO ₂ ceramic composite containing 40 vol% tetragonal ZrO ₂ . The neutron-diffraction data were analyzed using the Rietveld refinement technique, which allowed determination of the extent of the transformation, as a function of temperature....

article

Thermal expansion anisotropy in hot-pressed SiC-whisker-reinforced alumina composites

P.F. Becher, C.-H. Hsueh, S.B. Waters

Materials Science & Engineering A > 1995 > 196 > 1-2 > 249-251

The measured linear thermal expansion coefficients α of hot-pressed SiC-whisker-reinforced aluminas decrease as the SiC whisker content is increased from 1 to 60 vol.%. However, owing to the preferred orientation of the whiskers, the α value for each SiC whisker content is greater in the direction parallel compared with the direction perpendicular, to the hot-pressing axis. The observed behavior is...

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Acta Materialia (4)
Materials Science & Engineering A (3)
Applied Surface Science (1)
Composites Part B (1)
Dental Materials (1)
Intermetallics (1)
International Journal of Solids and Structures (1)
Journal of Non-Crystalline Solids (1)
Physica B: Physics of Condensed Matter (1)
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